I started putting the stuffing gland in the lid near the handle, this stopped the cables being damaged when thrown in the van at the end of the day. However we've now moved over to battery tools as no one likes carrying a transformer up several flights of stairs to drill a couple of holes...
I heard a story about one guy, who to save buying 110 V power tools required on a construction site, he directly wired the 240 V input to the 110 V sockets, and changed all his 13 A plugs to 16 A 110 V ones. Now one ever checked, even though his power tools all had colour black cables instead of the correct colour yellow. Nice rewire JW. Thanks for sharing.
Chris Walford I think I get it. So you mean he wired the 110v leads and sockets straight into the 230v supply with no transformer, replaced the plugs on his tools for 110v ones and so ran his 240v tools at 230v on site. Very crafty. I’m surprised nobody noticed that there was no transformer. It would have been more crafty to have had a transformer case with a brick in it that was wired straight through. This shouldn’t happen on our sites because all 230v MDU are padlocked and we supply and regularly test the 110v transformers and cables.
Hi John, lovely masterful descriptions of the products and how they apply to any standards. Keep up the good work. I wonder if we finally get control of the public media again. These kinds of videos should be on like adverts between programs. Public safety films like we used to have years ago.
As already noted, there should be a thin foam black gasket under lid so evidently this thing has been apart before. Also I would have plugged the unused screw hole beside your domed flex gland with mastic to prevent any water ingress, I know you said it's for indoor use only but you never know..
You should always leave the PE (Protective Earth yellow/green) LONGER than other wires because this is portable device. It must be the longest because if the mains cable loosens, it cuts off last. The inner connections look very bad. The protective earth should never be connected that odd way. This looks really weird to me. Is this some kind of homebrew apparatus?
There should have been a gasket under the lid , they are made of fiberglass filled plastic (GRP) the potting is about 20mm thick then they are filled with sand, that is the original cord grip for these, they are still made just like this. I often replace with a standard 20mm compression gland in backwards I find a step cutter works best
I never knew about 110V devices. They aren't used where I live. Actually that is pretty clever, after transforming they are much safer for sure! Not sure why the output is middle earthed though instead of floating. I used to use isolated 230V power outside and in the garden, just because I had an extra isolating transformer laying around and there is no residual current protection in my house (besides room with a shower). Totally isolated and floating like on an electronic workbench can never be a bad thing :)
Centre earth means any fault to ground is only 55V. Floating would be ok until a 1st fault occurred, then it would be 110V to earth when a 2nd fault occurred.
I had the exact same transformer years back -I was working of a scaffold and each night we lowered the tools down via a rope and pully the last piece of equipment was the transformer which as soon as offered it over the side of the scaffolding the handle broke clean off and it dropped to its death hitting various pieces of the scaffolding on the way down like a pinball machine / the poor apprentice on the ground didn’t know where to run 😂
The transformer is supposed to be NEAR the mains socket, preferably indoors. You should then run 110 volt extension leads out and up the scafolding. The whole point of 110 volt is to prevent running 240 volt cables across outdoor works
@@drivewasher what a nonsense 110 volt powertools. We dutch run 230/400 volt cables on construction sites and on scaffolding. Tools are dubble insulated every user socket is protected with 30mA rcd, sockets has a springloaded hatch/flap distributionboxes ip 66 watertight, permanent shaffonding is connected to ground with there own ground rod.
Hi John, I think you videos and short lectures are great, not only explaining theory but lovely practical demonstrations. I really like the one with the 0.5mm^2 wire and plug. I think we should ban Ebay electrical goods from certain countries completely, China etc. I have tested some of their copy switches and the results are surprising. Contacts that should be brass with brass links are actually plated steel. The result showed they would overheat at their rated current. And they were UL, CE and CSA certified. Just lovely down to earth videos all understood very well. great little lectures so thankyou.
Mine is about 80 percent filled with resin and came new with the backward stuffing gland. Seems odd that they use a choccy block and not crimps though I guess it's good practice to open it up now and again to check that the outlet terminals are tight. I only read recently that the outlet mounting screws etc don't need to be earthed as they're small and ancillary. I should source such a comment however... Flex is likely to be H05 or H07 RRF or RNF. Rubber on the basic insulation and rubber or synthetic rubber for the sheath. 07 is higher voltage rating ie thicker and more durable sheath. H07RNF is used as standard on stage lighting rigs etc I was waiting to see what you used to fill the old cable clamp screw hole in the fibreglass- bit of silicone or epoxy to keep the dust out?
I've lost count of the number of these I've repaired. Strangely, or not as the case may be, all of the issues were damage due to 'user error' ie smashed sockets or damaged cable due to people walking them like a dog. I did come across a large 30vac transformer that wasn't showing continuity across the primary. On closer inspection the potting had a huge crack through it... Scrap.
I remember years ago an 'electrician' connecting 415v to the 110 side and 'large' sparks from the 240v side, seemed loads of fun at the time. This is when I was kid helping dad on a site - which would never happen now of course...
Hi John thank you for your thorough step by step guide to repairing this transformer, very helpful. I notice you didn’t seal the original cable restrained bolt hole through the case adjacent to the cable entry hole. The other thing although I may have missed it, did you test the actual output voltage under load conditions. Thks
Why were not wire end ferrules used to connect the neutral and ground wire in the terminal? When tightening the screw terminal, the fine copper wires are squeezed and sometimes severed - thus creating a cross-sectional reduction, which may even lead to fire!
Probably only an issue when really heavy duty tools are used for extended periods of time. This particular unit seems to be for experimental and occasional use. That said, I'd feel comfier with ferrules!
Thanks for shareing this video. i have purchased used 5kva transformer from ebay and notice that they have removed the Thermal Overload Switch which is fitted next to 230v main power cable. If i need to place it back, whats the ideal device that i should need to buy. (amp etc) and will it be any issue if i continue to work without this switch ? Thanks
what was the rating of the circuit breaker.,, why was it on the primary and not the secondary..i have one of these but it has a 20amp circuit breaker4.....and a mains plug with 13a fuse...surely that wont work
with the advent of better battery tools these have become bit of a unicorn but you still see them every now and then oh and one of my first jobs as an apprentice was to replace leads on trannys i must have done about a thousand !!! my tool kit consisted of two screw drivers from my dad ( pozi 2 and a terminal ) a pair of his old Elliot Lucas pliers and a 10 inch Bowie knife my uncle bought me back from Texas !!! you can imagine that wouldn't be acceptable today pulling out a brass backed hunting /fighting knife to score a bit of flex !!!
That's a very clever idea, you can use regular 110V appliances, but only 55V to ground. Is the UK the only place where this is used? In Portugal there is no such thing, and you can't buy 110V power tools anywhere even if you wanted to.
Yes, and it's a requirement on most construction sites, at least for external work. It's especially important in damp climates when builders are often working in wet, muddy conditions.
I also thought it was a very clever solution! Never seen anything like it here in Australia, but all our stuff uses RCDs and generally is much drier than the UK. Never thought that one if the reasons why it would be in use is because of the damp climate, but makes sense now.
@@Berkeloid0 RCDs are used in the UK too, but as with any device, they aren't 100% reliable and in a wet environment they are going to be prone to nuisance trips. Also, some of the types of devices used in construction sites can trip RCDs on start-up unless they have characteristics which allow for it (and those characteristics are not the best for protecting people). The 55+0+55 system is inherently safer. For the same reason telephone systems which (usually) have a nominally 50V DC supply superimposed to provide low power and diagnostics was limited to 50V for safety reasons. Fortunately, the availability of Li-Ion powered kit has replaced a lot of the need for mains-powered portable kit in construction sites. There are now very capable SDS drills, circular saws, jigsaws etc.
t0nito - the same 110V yellow socket outlets are found in some industrial buildings, fed via fixed 230/240V to 55 - 0 - 55 transformers so that 110V power tools can be used.
That block connector and flapping about in the breeze is well dodgy. I can't believe it was like that from new. I think it fair to say some muppet has been there before.
When I next get mine out I will take it apart. Mine has a broken flange on the fuse holder which I think was original. The circuit breaker is the only outwardly difference to my transformer. I found it odd that the circuit breaker was on the primary winding. I thought you had a correct fuse in the plug of the transformer ? and the fuse was on the secondary to protect the transformer. ?
Inrush current is a bit more involved than you suggest. The flux in an inductor core is the integral of the applied voltage, and related to the current drawn.. If you apply DC to an inductor then the instantaneous flux and current will be zero, even in a perfect inductor with zero resistance.. In a perfect inductor you would get perpetually linearly rising flux and current, in a real inductor the increasing current through the resistance would eventually make the inductor voltage zero so you'd end up with steady state current determined by the resistance. With AC it depends where on the waveform you switched. Switching at peak voltage would give no inrush current, you'd be integrating from sine maximum to sine minimum so the peak flux and current would be the same as you get on every other cycle. If you switched at zero crossing you would get an inrush current as you would be integrating over a half cycle from zero to zero which would give higher peak flux, and if that was enough to saturate the core you would get a much higher current.
@@dkek383 I'm not able to think about this mathematically, but I've always imagined that an inductor presents a high resistance to a sudden change in voltage. The changing magnetic field seeks to generate a current which opposes the one which created that field in the first place. It's also known as Lenz's law. How can an inductor draw a surge current when suddenly presented with a voltage? That's what capacitors do. PS I'm being a bit lazy with terminology when referring to resistance/impedance/reactance.
HI John, at 0:35 you say that the output is centre tapped to ground, but when you test it at the end you get >500 meg between output line and earth. If it's centre tapped to ground wouldn't that show almost a DC short in that test?
I have not found any official standards but two private websites who say site transformer are grounded on the secondary. His measurements do indeed indicate the the secondary is floating. Perhaps the secondary "ground" is isolated from mains ground just like on a portable generator?
The insulation test is DC. DC does not go through a transformer. Insulation test was between the 13A pug (primary winding) and the output earth (secondary winding). If he'd tested between the output connections and output earth then the insulation would be almost zero.
Hauptwerk Hardware - on all the 110V CTE (55V - 0 - 55V) portable or fixed transformers that I have encountered, the transformer secondary mid tap is connected to earth. So a multimeter on the resistance range should show continuity between either of the 55V line output socket terminals and any earth connection (be it the output earth terminal or the mains input earth).
Weeble Wobble - no, because the DC test current should flow from the mains plug earth terminal to the transformer mid tap, through the copper winding of the secondary and to the output terminal on the 110V socket.
Its odd the "original" cable being loose to the metal case but the solution was simple and good: Nice work JW. Many appliances have one screw that is different because it gets the most handy at the time and forgot to replace with equal....
I put ferrules on all stranded cable in screw terminals now. They're so cheap, and the crimp tools aren't exactly expensive either. Crimping an end on barely takes any longer than twisting/doubling up a stranded cable. It's a habit I got from wiring narrowboats (where all of the mains cable is stranded and sockets aren't designed to accept stranded cable) which just stuck with me as a sensible idea for everything else.
Robin Whitfield - the company that I’m employed by has over fifty years experience of using stranded tinned copper wire terminating in screw terminal block / choc blocks that have wire protectors. Our failure rate on these is extremely small and we have millions of terminals.
Fick dich - no, because the DC test current should flow from the mains plug earth terminal to the transformer mid tap, through the copper winding of the secondary and to the output terminal on the 110V socket. On all the 110V CTE (55V - 0 - 55V) portable or fixed transformers that I have encountered, the transformer secondary mid tap is connected to earth. So a multimeter on the resistance range should show continuity between either of the 55V line output socket terminals and any earth connection (be it the output earth terminal or the mains input earth).
Why not put a squirt of hot melt glue or a small rubber bung in that screw hole next to the gland nut to prevent water ingress in the rain or if the transformer ends up in a puddle?
Really great vid JW. Came here trying to work out whether there was a standard for the non earth pins in the 110v socket. No clues from the wiring seen in this video. Is there a live or neutral after the step down in the induced coil. Grey doesnt really provide much of a clue.
question , can you use these transformers as a voltage converter for US appliances in the UK ? given that the continues rating is lower than the rating of the transformer
One the last part of the test you meggered between earth pin on 13a plug and 110v and got 500megs but you should have got near zoro because th e secondary has an earth on it.
The insulation test is DC. DC does not go through a transformer. Insulation test was between the 13A pug (primary winding) and the output earth (secondary winding). If he'd tested between the output connections and output earth then the insulation would be almost zero.
john flower - on all the 110V CTE (55V - 0 - 55V) portable or fixed transformers that I have encountered, the transformer secondary mid tap is connected to earth. So a multimeter on the resistance range should show continuity between either of the 55V line output socket terminals and any earth connection (be it the output earth terminal or the mains input earth).
Weeble Wobble - no, because the DC test current should flow from the mains plug earth terminal to the transformer mid tap, through the copper winding of the secondary and to the output terminal on the 110V socket.
So you just left a hole from the old screw open ??? so now damp can get inside through the hole ?? Also, was the brown leather tool wallet a BT phone engineers one ? I would have thought the internal earth connection would have been a Crimp Connection ? If it did have sand in it originally, then im guessing it would be for thermal reasons as well as damping the hum from the transformer ?
That’s only a good idea if your choc block is too big for your cable size. It doesn’t add any mechanical strength, except by filling up the hole a bit more.
@@JasperJanssen Whilst I appreciate your response. Singles can and will slide down the side of the thread of the screw and have floating wires in the terminal block. You're also less likely to cause crush damage to the wires with them folded - Especially when using flex. Good practice imo.
They weren't folded over originally, and it's lasted for 15+ years like that from the factory. The wires are large relative to the terminal block size.
Hi John , Great Video , can you draw a wiring diagram of the site transformer and show how the center tap works? I'm just curious to know how the voltage is being divided
If you knew how a cable gland works, you wouldn't ask. When used the "normal way" there is a round gripping clamp that squeezes into the outer sheath. That thing is right at the end of the domed clamp nut, and it is quite sharp. So, flexing of the cable is pushing it against that sharp edge inside the end of the gland. By reversing the gland, there ends up being a rounded edge plus the sharp thing is nowhere near the flexing point. Bottom line = the protection is BETTER with the gland reversed.
Many years ago I had to take a van load of this type of transformer back to their manufacturer to have their earths modified so that they could be used in telephone exchanges. Never could get any info on why, possibly something to do with earth potentials with GPO/BT systems. Any ideas?
A stupid question, but looking inside of that it looks as though it is earthed to the neutral. Am I correct in thinking that or have I just seen it wrong?
My father,while recovering a stolen car from a construction site that was finishing up noticed that they were literally about to throw about 20 brand new ones of those into a skip,he bought them home and they just sat in our garage for 20 odd years before he gave them to a scrap man😄.
If you don't mind me asking, is the 110 volt coming out of this transformer, AC or DC current? Sorry about the ridiculous question! Thank you very much for uploading this video. Kind regards, Dan George
I have a site transformer that I use at home with 110 tools but it keeps tripping the earth leakage, mostly on turning it off but occasionally when turning on. Does not appear to be any fault with the transformer, could the secondary be unbalanced?
@@jwflame I will get that checked again, the wiring in the garage where I use the transformer was only installed two months ago, and last night the transformer tripped the 32 amp ring main breaker instead of the earth leakage. I think that they might have used the wrong grade of breakers despite being told that I was going to be running welders and other equipment in there I have a 32 amp socket on a seperate breaker for the welder they installed so they obvious ly understood what was required.
@@mernok2001 say you have two fuses connected to an RCD. There is a small leakage or short between ground and live on fuse 1. You connect a big load on fuse 2, a small portion of the current going back through neutral on fuse 2 will go out through neutral on fuse 1 and from there to ground. Thereby tripping the RCD.
Can't believe he didn't know how the original cable grip works, trying to pull the cable outwards tightens the gripper, once the screw is loosened simply push the cable inwards and the insert comes out, LOL!!!🖖😁
after a bit of searching answered my own question The system has its origins in the 1949 Annual Report of HM Chief Inspector of Factories, which recommended the system for use on building and construction sites and other applications involving large-scale use of portable electric tools. The system was described in the British Standard Code of Practice, CP 1017:1969, Distribution of Electricity on Construction and Building Sites (superseded by BS 7375:1991, now BS 7375:2010). Equipment was specified in BS 4363:1969 Specification for Distribution Assemblies for Electricity Supplies for Construction and Building Sites (now BS 4363:1998+A1:2013, also BS EN 61439-4:2013). referenced from IET autum 2016
Roly M Early ones had Reyrolle BS 196:1961 5 and/or 15 A outlets which were also yellow, but the casing was metal rather than plastic and I think painted with Hammerite; certainly the whole thing wasn’t yellow. I’m surprised how small the actual transformer is for 3 kVA, but I suppose that’s only a tool rating. What is the rating for continuous loads such as site lighting?
In theory yes - the earth connection to the secondary needs to be accessible so that it can be removed. Voltage output is still 110V however, so not really of much use.
you could make a pretty good step down transformer for travel purposes. if you're visiting the UK/Europe from the states. But due to the high in duction of first plugging in the transformer of that size, it be more practical in theory.
Jonathan Furtado - eh? It is a step down transformer! You can connect most electrical items from the U.S.A. (or any other country that uses 110V/115V/120V) to these transformers. The only limitations are the rated power of the item has to be no greater than the rating of transformer (keeping in mind that these transformers are often tool rated, the continuous rating is lower) and any device that needs the supply to actually be 60Hz (clock/timer) will run slow.
JW referring to your reply, if you were really desperate, or bored, you could get a second tranny and fix 110V O/P of first tranny to 110V O/P of second tranny which will act as a step up giving you 230V. I can't think why on earth you would want to do such a thing in real life but it's possible
Love your videos John - looking at most modern fixed 13 amp fixed plugs and the pins are made of metal rather than brass - is there any advantage of having brass pins on plugs ?
NO. A 110volt tool connected to a United Kingdom 230volt 3 pin socket will blow the 13amp fuse. This is because a 110volt tool has a lower resistance than a 230volt tool and as a consequence will pass too much current. Should some idiot replace the 13amp fuse in the 3 pin plug then the tool will burn out.
I love them cable grips (the one you threw away), when the screw is removed, the rear insert comes out, releasing the mains lead. (I noticed a bit of sand in it, so pliers might be useful). I use them on my reel to reels.
@@JasperJanssen I recognized the cracking on the jacket. The rubber, or whatever it's made of, has deteriorated and had begun to crack. It was just accelerated at the joint because of stress. In less than 5 years you'll see a repeat failure and the rest of the cord will show its true condition. Having a nice emergency off switch can't be a bad thing.
Why the resistance between the incoming ground and L or N on the output is >500 MOhm at ruclips.net/video/2t_JR0CxctQ/видео.html ? I thought this is a center tap transformer with the center connected to the incoming ground as it on this wiring here ruclips.net/video/fRhofcMyAyk/видео.html
Hello sir, can these transformers be used to power audio equipment as is? I am assuming the center tapped ground would cause grounding loop issues, especially if using audio equipment in conjunction with other equipment connected to the 240v mains.
Not really, as you are going from a flexible cable to a solid core. Should have a fixed terminal on the case so any flexing of the input wire does not stress the solid wire and fatigue it. The solid wire is the transformer primary, and if you break it off at the most common point, the place where it goes into the potting, you now have a very heavy paperweight. Ferrules on the CPC however are fine, they are both flexible cables. John should have taken some sandpaper to the top epoxy to clean a spot, then used solvent to degrease the spot before putting on a cable tie base and 3M VHB foam to hold the base, then a cable tie to hold the floating connector block to the top there. Less stress on the solid wires. The original gland is easy to take apart, just push the wedge back out the back, or use the cable stub to pull it out, and then reuse it again. Those glands are quite strong, you can easily hang the transformer on it with no problems, the cable will break before the gland lets go. Cable is a silicone rubber cable, rated for use in Arctic conditions, and also rated for use in water, so it is waterproof and still flexible at -55C, and can be used up to 130C. You normally find it used on pond pumps, and I have made quite a few extension cords out of them when the pump fails, or if, as I was doing, I only needed a 50cm tail on the cable, and the pumps come standard with 10m.
BS 7671 Regulation 526.9.1 In order to avoid inappropriate separation or spreading of individual wires of multiwire, fine wire or very fine wire conductors, suitable terminals shall be used or the conductor ends shall be suitably treated.
@@garymckeown4278 as an apprentice I was taught to twist and double but that was through lack of knowledge and the fact it takes longer but once you know it's wrong why would anyone continue to do it. It doesn't make you popular when you fail entire marinas where the pontoons are all wired in h07-rnf without a single boot lace ferrule in sight when the client has only recently rewired it.
Cooling, Many of the users of these transformers would have them supplying 110v volts for a large amount of time during the work day. The sand would reduce the chances of the transformer overheating but it also would make it heavy, maybe they deliberatley removed the sand to make it lighter.
Those are known by several common names, the correct designation is IEC 60309, it is now an international standard for "industrial connectors". They are strongly color coded for voltage and have the earth/ground pin in a different "Clock position" based on that voltage color correlation. The ones in the video are IEC 60309 4h 16/20a. Common colors are Yellow for 100 ~130 VAC, Blue for 200 ~ 250 VAC, Red for 400 ~ 480 VAC (230/400 Three phase being most common for red), There are several less common colors but one in particular that may be of interest to you is Orange, Orange is only found in areas that use split single phase that wish to distribute to the end point at 120/240... that would be North America. Orange came about as part of series 2 certification for IEC 60309 plug and socket type pin & sleeve devices for use in North America. You can get these in North America but their use has primarily been industrial, but are gaining traction as replacements where proprietary pin & sleeve designs were already popular. Most smaller North American domestic sockets (NEMA) are just that, for domestic use, but in general are absolute garbage in the shop, do they work yes... are they going to survive being stepped on... well once or twice. A 60309 takes allot of abuse, I actually use these on all my portable power tools, and since I attempt to only buy 50/60hz small tools, I can use them anywhere in the world with a proper local adapter and/or transformer. Wikipedia has a nice table of voltages and configurations which offers a basic introduction to the system. en.wikipedia.org/wiki/IEC_60309 Edit: P.S. In North America they seem to be ridiculously expensive, but can be had cheaply if you keep a watch, I have boxes upon boxes of them I've picked up for reasonable prices, so I always have them at hand when I want one.. they really are superb.
Because then it would just be an isolation transformer, this is a site transformer - in which the whole point is to give it a centre tap. Though you can omit the extra earth connection yourself on some of these transformers if you so desire
Because then a short between primary and secondary in the transformer would not blow a fuse and would make the secondary side live at up to 1.5 times mains voltage relative to Earth.
@@petehiggins33 That's not true, omitting the centre tap doesn't make much difference it just makes the output 0v - 110v rather than 55v - 0v - 55v. The primary and secondary core cannot short together because they are only connected via a magnetic coupling not an electrical one - even so the power is supposed to flux between the primary and secondary coils to make it work anyhow
Ben Vahanian - because the whole point is to keep the voltage of any accidentally exposed conductor as low as possible. In a damp or wet construction site environment, it may be troublesome to maintain the system to be earth free. And the system would have to undergo regular testing to find out or confirm if it is earth free. By earth free, I mean all the 110V supply equipment, all the extension leads, all the tools etc. would have to have absolutely no insulation faults. It all would have to be tested with a insulation tester. This is not very practical. Why? Well if any of the conductors suffered an insulation fault (say a cable snagged on a piece of metal that was lying on the ground), your isolated earth free 110V system would now be an earthed 110V system. If a second fault was to occur, say a worker damaged the flex going to a power tool they were using, but did not notice. And then later on accidentally made contact with the conductor. If this was the now ‘hot’ conductor, they would complete the 110V circuit to earth/ground and could receive an 110V electric shock which could electrocute them. Even if no second fault occurred, it would fail the next insulation test. Bringing the job to a halt. Hence the solution is to centre tap the secondary winding of the transformer. Now by having an intentional proper earth, if either of the hot lines becomes earthy due to an insulation fault and a high fault current flows, the overload device will trip. Even if no significant fault current flows, if a worker accidentally makes contact with either one of the conductors, the maximum voltage that they would experience would be 55V. It is unlikely that this voltage will cause them injury. Hence this is the safest system.
C'mon John. You know it's not 230V and 400V. You know they haven't changed the taps on the transformers. Test your own input and do a video to showing what your voltage is.
Voltage here is about 250V. You are right in that the actual voltage hasn't changed in most places, but the declared voltage is 230V, and 230 is what's used for calculations, even though the actual voltage isn't usually 230V in reality.
Do you know what they *actually* changed the nominal voltage to? Here in Australia, a couple of years ago the area I live went from 240V +/- 6% to 230V +10%/-6%, which means the maximum allowed mains voltage dropped from 254.4V down to 253V. So in other words, the nominal voltage went to 230V but they didn't have to change any taps on the transformers... Although in our case they actually had a sensible reason for making this change. It seems there were so many grid-tied solar systems being installed that it was pushing the voltage too close to the limit, so by lowering the nominal voltage to 230V it means they can slowly go around changing the taps in areas that feed in a lot of solar power, and they don't have to worry about the voltage dropping below the spec on cloudy days when nobody is feeding in.
Center-tapped 110V? That's rather odd. What are those sockets? They don't look like US plugs would fit, which is what I'd expect on a 110V power tool. I didn't think 110-120V service was commonly used outside North America. The problem with reversing the cable gland is that the gripping fingers are directional. I'm surprised you don't have step bits for conduit sizes. Nylocks are a good choice, but I would probably go for blue Loctite (242). One bottle fits all screws.
It's a weird British thing, for safety purposes. These are used on construction sites, where there's a lot of potential to contact live wires while grounded. They have special tools as well, designed to work on 110v 50hz current (here in the US, it's 60hz, so our tools would theoretically work fine on one of these transformers, just slower.) The transformer is connected similar to our 240v appliances- the outside transformer in the US supplies 240v, with a center tapped neutral that is referenced to ground. In this case, it's a center tapped 110v transformer, with the center tap referenced to ground. That way, if a worker comes in contact with a live wire, it's at most 55v to ground, which is much less likely to cause injury or death. As for the different plugs, there's lots of different standards. Something similar to ours are used in China, but on 240v.
puckcat22679 - most electric drills used in most tools are actually DC motors fed via rectifier diodes. So these would not care if the supply was 50Hz or 60Hz. Secondly, not all AC motors care much about the mains frequency, as long as it is in the correct range. So again there would be no significant speed difference. The connectors are actually an international standard, look up IEC 60309
Actually almost the worst you can do, as then there is no remnant field from the previous half cycle to provide back EMF. With these a much better protection is an appropriately sized NTC inrush limiting resistor, and for larger loads you then also have a relay and time delay ( around 5 mains cycles) after power on that then shorts out the resistor. That provides enough impedance to reduce the start up surge, and still allows protection devices like fuses to act in case of a shorted output properly. I have a 2kVA variac that I did that to to reduce the inrush surge to a low enough level that it would not trip the 30A breaker it was attached to, and also not trip RCD breakers.
Actually zero crossing gives the wort case surge with a transformer. The reason is that when a transformer is running open circuit, being an inductor, the current lags behind the voltage by 90°. So normally when the voltage is crossing zero, the current is at its maximum reverse polarity and over the next half cycle of voltage it goes though zero and then to its maximum positive value. If the current starts at zero then over the first half cycle it will rise to twice its normal value. That would not be too bad except for the fact that transformers usually run with their core close to magnetic saturation for efficiency reasons. That means the core saturates during start-up. The inductance disappears and then the only thing limiting the current is the DC resistance of the primary, so the current can be enormous. Counter intuitively, the best time to turn a transformer on is when the mains is at its peak voltage.
With the transformer primary uninsulated wires flapping around and having the potential to touch each other (but probably not), I would have been tempted to fasten them down or put some insulation over at least one of them just to be on the safe side.
Yup, enamelled wire. But I'd still have been tempted to add some sleeving :-) Also I'd have used a 3-way choc block, LEN, so any future flex cable change didn't need a re-crimp; and glued or bolted it down, to avoid any wiggling of the transformer wires... :-)
Yep I know but enamelled can crack and ware off when things are touching and not fastened down. Put it like this, I would not risk holding an enamelled wire that was live if it had been able to move around freely. Not even sure I would want to anyway. In the transformer the windings you essentially have double the insulation between the windings and they are fixed and still. No cracking, flaking in the enamel should occur when totally still. But the wires are out in the open and can flex/move a bit, all bets are off (in my opinion).
This is a typically convoluted and cumbersome British "solution" to a fairly trivial problem. Use a huge heavy transformer box with huge inrush that trips normal circuit breakers, so site must provide special outlets and wiring. Requires all tradespeople to buy a second set of tools with US plugs that operate on 110V. Giant box contains no short circuit protection, so shorts to ground or between "Lines" will cause big current and unsafe fault on the tools' cable. No switches on the 2 outlets. Elsewhere in the world we use a 220/240V unit with standard sockets, so normal tools can be used. Inbuilt RCD protects operators against shorts to ground. Inbuilt short circuit protection protects the gadget and wiring. 4 individually switched outlets, 10A or 15A. Light weight and low cost. Example: www.gettoolsdirect.com.au/portable-power-board-4-way-15amp-outlet-pp015t.html
It's really not that bad. Consruction sites have 110V power from dedicated transformers, such as www.blakley.co.uk/products/transformers/site-transformers-4kva-to-20kva/site-power-transformers/tap320s12 all of which have circuit breakers on the outputs to disconnect if short circuits or overloads occur. All tools and lighting on construction sites are 110V, and if people want to use those tools elsewhere they have a small transformer such as the one in this video. No one buys 2 sets of tools. They don't have those dreadful flimsy US plugs either. RCDs and 230V can in theory be used, but they never are. 110V with 55V to ground is reliable and safe. RCDs need to be tested often and would be quickly damaged/destroyed on a typical construction site, which in the UK will frequently be soaking wet.
1. That remaining blue crimp doesn't look like its been completely squeezed down properly. The open end is still circular. 2. I would have added sleeving to those two bare copper wires so that cannot directly touch each other. 3. I would have added a neon indicator to show when it has power.
NO! You don't put the old bolts and nuts in the bin! Even though there are only 3, not 4, you can keep them to reuse for a future project. Same with the original cable grip. There must be a way to open it to remove the damaged piece of cable and put the good cable through. Also you can reuse the original spade connector. put a piece of heatshrink tube over the incoming wire, strip and solder the wire to the short piece of wire still on the spade connector, slide the heatshrink tube back over the solder joint and shrink it. RECYCLE the copper from the damaged piece of cable.
Solder wires to the stub on the spade connector? Please don't. The price of a spade connector is not worth the time or effort of bodging it back on, not to mention that it looks incredibly unprofessional. Have some pride in your work, and people will respect you for it. Doing poor work in order to save a few pennies does NOT look good!
(9:45) - *_Not that this should of course be outside where there's water..??_* Excuse me but aren't they designed to be used on building sites? Like, building sites that are open to the elements? Sorry John but I have to disagree. These transformers are very much designed to work outside. Under the pouring rain. And I don't think I'm wrong here. >
This one is a portable transformer designed to be located indoors, and 110V items attached to it for use outside. Larger building sites would have a much bigger transformer with multiple outlets, located in a single location away from where the tools and other items are being used. The point is to keep the 240V away from the work area, otherwise there isn't any point in using 110V tools. Using a portable transformer with a 240V extension lead and standing next to the transformer outside with a tool connected on a short lead is totally the wrong way to use it.
Wow. It wasn't exactly a difficult or time consuming job though, was it? It's not like it took him several extra hours of unnecessary work. If he prefers the new one that's up to him.
Please do not hit things with the palm of your hand, you have a whole lot of nerves running through there. Mess them up and your in trouble. Other than that, thanks for the video.
Most houses today in the US have two 110 volt wires and one neutral wire running into the house from the local distribution system. These wires can run underground or above ground. If there are two 110 volt wires running to the house, then the house has 220 volt service and appliances, such as dryers and air conditioners.
I think every old 110V transformer I’ve ever seen has at least one odd screw on the top! Great video as always!
I always have to replace at least one when PAT testing
I always used nyloc nuts. They just get loose in transit otherwise.
Artisan Electrics My wife often says I have an odd screw on top.....
It's common to loose a washer or a screw 😂
I started putting the stuffing gland in the lid near the handle, this stopped the cables being damaged when thrown in the van at the end of the day. However we've now moved over to battery tools as no one likes carrying a transformer up several flights of stairs to drill a couple of holes...
I heard a story about one guy, who to save buying 110 V power tools required on a construction site, he directly wired the 240 V input to the 110 V sockets, and changed all his 13 A plugs to 16 A 110 V ones. Now one ever checked, even though his power tools all had colour black cables instead of the correct colour yellow.
Nice rewire JW. Thanks for sharing.
Bet he took twice as long as everyone else to finish his jobs though!
trickyd2013 uhm... why? You mean he took a quarter of the time, right?
Apart from the safety aspect, 240V motors work better than 110V.
Jasper Janssen 240v motor running on 110v is faster?
trickyd2013: no, he put 110v c-form plugs on 240v tools
Chris Walford I think I get it. So you mean he wired the 110v leads and sockets straight into the 230v supply with no transformer, replaced the plugs on his tools for 110v ones and so ran his 240v tools at 230v on site. Very crafty. I’m surprised nobody noticed that there was no transformer. It would have been more crafty to have had a transformer case with a brick in it that was wired straight through.
This shouldn’t happen on our sites because all 230v MDU are padlocked and we supply and regularly test the 110v transformers and cables.
Good idea putting the gland that way round JW. Will do the same with mine.
Hi John, lovely masterful descriptions of the products and how they apply to any standards. Keep up the good work. I wonder if we finally get control of the public media again. These kinds of videos should be on like adverts between programs. Public safety films like we used to have years ago.
As already noted, there should be a thin foam black gasket under lid so evidently this thing has been apart before.
Also I would have plugged the unused screw hole beside your domed flex gland with mastic to prevent any water ingress, I know you said it's for indoor use only but you never know..
You should always leave the PE (Protective Earth yellow/green) LONGER than other wires because this is portable device. It must be the longest because if the mains cable loosens, it cuts off last. The inner connections look very bad. The protective earth should never be connected that odd way. This looks really weird to me. Is this some kind of homebrew apparatus?
I think it has been repaired before, the terminal block was the clue.
There should have been a gasket under the lid , they are made of fiberglass filled plastic (GRP) the potting is about 20mm thick then they are filled with sand,
that is the original cord grip for these, they are still made just like this.
I often replace with a standard 20mm compression gland in backwards I find a step cutter works best
why the sand ?
@@cagmito76 stability, some use weights
@@cagmito76 protection from impacts, and I would suspect the same as fuses extinguishing any arcs or flames
I never knew about 110V devices. They aren't used where I live. Actually that is pretty clever, after transforming they are much safer for sure! Not sure why the output is middle earthed though instead of floating.
I used to use isolated 230V power outside and in the garden, just because I had an extra isolating transformer laying around and there is no residual current protection in my house (besides room with a shower). Totally isolated and floating like on an electronic workbench can never be a bad thing :)
Centre earth means any fault to ground is only 55V. Floating would be ok until a 1st fault occurred, then it would be 110V to earth when a 2nd fault occurred.
@@jwflame That makes sense. Pretty interesting concept!
I had the exact same transformer years back -I was working of a scaffold and each night we lowered the tools down via a rope and pully the last piece of equipment was the transformer which as soon as offered it over the side of the scaffolding the handle broke clean off and it dropped to its death hitting various pieces of the scaffolding on the way down like a pinball machine / the poor apprentice on the ground didn’t know where to run 😂
The transformer is supposed to be NEAR the mains socket, preferably indoors. You should then run 110 volt extension leads out and up the scafolding. The whole point of 110 volt is to prevent running 240 volt cables across outdoor works
Steve Ashcroft yes correct
@@drivewasher what a nonsense 110 volt powertools. We dutch run 230/400 volt cables on construction sites and on scaffolding. Tools are dubble insulated every user socket is protected with 30mA rcd, sockets has a springloaded hatch/flap distributionboxes ip 66 watertight, permanent shaffonding is connected to ground with there own ground rod.
I cringed at first with the cable gland arse about, but think about it... Bloody ingenious!
Yes and not reuse the original clamp ,he talks a good job
Haha don't collect manky old screws very modern he will go far
Hi John, I think you videos and short lectures are great, not only explaining theory but lovely practical demonstrations. I really like the one with the 0.5mm^2 wire and plug. I think we should ban Ebay electrical goods from certain countries completely, China etc. I have tested some of their copy switches and the results are surprising. Contacts that should be brass with brass links are actually plated steel. The result showed they would overheat at their rated current. And they were UL, CE and CSA certified. Just lovely down to earth videos all understood very well. great little lectures so thankyou.
Mine is about 80 percent filled with resin and came new with the backward stuffing gland. Seems odd that they use a choccy block and not crimps though I guess it's good practice to open it up now and again to check that the outlet terminals are tight. I only read recently that the outlet mounting screws etc don't need to be earthed as they're small and ancillary. I should source such a comment however...
Flex is likely to be H05 or H07 RRF or RNF. Rubber on the basic insulation and rubber or synthetic rubber for the sheath. 07 is higher voltage rating ie thicker and more durable sheath. H07RNF is used as standard on stage lighting rigs etc
I was waiting to see what you used to fill the old cable clamp screw hole in the fibreglass- bit of silicone or epoxy to keep the dust out?
I've lost count of the number of these I've repaired. Strangely, or not as the case may be, all of the issues were damage due to 'user error' ie smashed sockets or damaged cable due to people walking them like a dog. I did come across a large 30vac transformer that wasn't showing continuity across the primary. On closer inspection the potting had a huge crack through it... Scrap.
I love the understated humour in these videos 😂
I remember years ago an 'electrician' connecting 415v to the 110 side and 'large' sparks from the 240v side, seemed loads of fun at the time. This is when I was kid helping dad on a site - which would never happen now of course...
Hi John thank you for your thorough step by step guide to repairing this transformer, very helpful. I notice you didn’t seal the original cable restrained bolt hole through the case adjacent to the cable entry hole. The other thing although I may have missed it, did you test the actual output voltage under load conditions. Thks
Why were not wire end ferrules used to connect the neutral and ground wire in the terminal?
When tightening the screw terminal, the fine copper wires are squeezed and sometimes severed - thus creating a cross-sectional reduction, which may even lead to fire!
Probably only an issue when really heavy duty tools are used for extended periods of time. This particular unit seems to be for experimental and occasional use. That said, I'd feel comfier with ferrules!
John, why did you not do a final test on a heavy duty drill or similar tool?
Surprised to see you using the same screwdriver on both Pozi and Phillips screws!
The screws on this are likely knackered enough that it makes no odds!
Thanks for shareing this video. i have purchased used 5kva transformer from ebay and notice that they have removed the Thermal Overload Switch which is fitted next to 230v main power cable.
If i need to place it back, whats the ideal device that i should need to buy. (amp etc) and will it be any issue if i continue to work without this switch ?
Thanks
what was the rating of the circuit breaker.,, why was it on the primary and not the secondary..i have one of these but it has a 20amp circuit breaker4.....and a mains plug with 13a fuse...surely that wont work
with the advent of better battery tools these have become bit of a unicorn but you still see them every now and then
oh and one of my first jobs as an apprentice was to replace leads on trannys i must have done about a thousand !!! my tool kit consisted of two screw drivers from my dad ( pozi 2 and a terminal ) a pair of his old Elliot Lucas pliers and a 10 inch Bowie knife my uncle bought me back from Texas !!! you can imagine that wouldn't be acceptable today pulling out a brass backed hunting /fighting knife to score a bit of flex !!!
Tipping the sand out makes it lighter to hump from site to site - or so I have heard..
That's a very clever idea, you can use regular 110V appliances, but only 55V to ground. Is the UK the only place where this is used? In Portugal there is no such thing, and you can't buy 110V power tools anywhere even if you wanted to.
Yes, and it's a requirement on most construction sites, at least for external work. It's especially important in damp climates when builders are often working in wet, muddy conditions.
Ireland uses these as well as the UK, not sure about anywhere else.
I also thought it was a very clever solution! Never seen anything like it here in Australia, but all our stuff uses RCDs and generally is much drier than the UK. Never thought that one if the reasons why it would be in use is because of the damp climate, but makes sense now.
@@Berkeloid0 RCDs are used in the UK too, but as with any device, they aren't 100% reliable and in a wet environment they are going to be prone to nuisance trips. Also, some of the types of devices used in construction sites can trip RCDs on start-up unless they have characteristics which allow for it (and those characteristics are not the best for protecting people).
The 55+0+55 system is inherently safer. For the same reason telephone systems which (usually) have a nominally 50V DC supply superimposed to provide low power and diagnostics was limited to 50V for safety reasons.
Fortunately, the availability of Li-Ion powered kit has replaced a lot of the need for mains-powered portable kit in construction sites. There are now very capable SDS drills, circular saws, jigsaws etc.
t0nito - the same 110V yellow socket outlets are found in some industrial buildings, fed via fixed 230/240V to 55 - 0 - 55 transformers so that 110V power tools can be used.
That block connector and flapping about in the breeze is well dodgy. I can't believe it was like that from new. I think it fair to say some muppet has been there before.
When I next get mine out I will take it apart. Mine has a broken flange on the fuse holder which I think was original. The circuit breaker is the only outwardly difference to my transformer.
I found it odd that the circuit breaker was on the primary winding.
I thought you had a correct fuse in the plug of the transformer ? and the fuse was on the secondary to protect the transformer. ?
Inrush current is a bit more involved than you suggest. The flux in an inductor core is the integral of the applied voltage, and related to the current drawn.. If you apply DC to an inductor then the instantaneous flux and current will be zero, even in a perfect inductor with zero resistance.. In a perfect inductor you would get perpetually linearly rising flux and current, in a real inductor the increasing current through the resistance would eventually make the inductor voltage zero so you'd end up with steady state current determined by the resistance. With AC it depends where on the waveform you switched. Switching at peak voltage would give no inrush current, you'd be integrating from sine maximum to sine minimum so the peak flux and current would be the same as you get on every other cycle. If you switched at zero crossing you would get an inrush current as you would be integrating over a half cycle from zero to zero which would give higher peak flux, and if that was enough to saturate the core you would get a much higher current.
So that’s why you switch inductive loads at zero crossing, it makes things harder! Yeah, sure.
Somewhere you’re making an error of reasoning.
@@dkek383 I'm not able to think about this mathematically, but I've always imagined that an inductor presents a high resistance to a sudden change in voltage. The changing magnetic field seeks to generate a current which opposes the one which created that field in the first place. It's also known as Lenz's law. How can an inductor draw a surge current when suddenly presented with a voltage? That's what capacitors do.
PS I'm being a bit lazy with terminology when referring to resistance/impedance/reactance.
HI John, at 0:35 you say that the output is centre tapped to ground, but when you test it at the end you get >500 meg between output line and earth. If it's centre tapped to ground wouldn't that show almost a DC short in that test?
I have not found any official standards but two private websites who say site transformer are grounded on the secondary. His measurements do indeed indicate the the secondary is floating. Perhaps the secondary "ground" is isolated from mains ground just like on a portable generator?
The insulation test is DC. DC does not go through a transformer.
Insulation test was between the 13A pug (primary winding) and the output earth (secondary winding).
If he'd tested between the output connections and output earth then the insulation would be almost zero.
The last test was between supply earth and secondary tap so open ins res is right.
I would have tested output voltage thou..
Hauptwerk Hardware - on all the 110V CTE (55V - 0 - 55V) portable or fixed transformers that I have encountered, the transformer secondary mid tap is connected to earth. So a multimeter on the resistance range should show continuity between either of the 55V line output socket terminals and any earth connection (be it the output earth terminal or the mains input earth).
Weeble Wobble - no, because the DC test current should flow from the mains plug earth terminal to the transformer mid tap, through the copper winding of the secondary and to the output terminal on the 110V socket.
Hi i lost some sand from bottom of mine..i fixed the hole..dont think i lost much ...is it still ok to use...thanks
Its odd the "original" cable being loose to the metal case but the solution was simple and good: Nice work JW. Many appliances have one screw that is different because it gets the most handy at the time and forgot to replace with equal....
But the case is yellow plastic.
@@simontay4851 Oops sorry yeah but it is plastic heavy dutty hard and and sharp on the edges, where soft cable would be torn and wear out
I personaly would have doubled the 1.5 flex where it went into the conector block to fill up the conector more
Better still, crimp ferrules onto the flexible strands.
I put ferrules on all stranded cable in screw terminals now. They're so cheap, and the crimp tools aren't exactly expensive either. Crimping an end on barely takes any longer than twisting/doubling up a stranded cable.
It's a habit I got from wiring narrowboats (where all of the mains cable is stranded and sockets aren't designed to accept stranded cable) which just stuck with me as a sensible idea for everything else.
No need to double up or use crimps if the screw terminal block / choc block has wire protectors (plates).
@@Mark1024MAK Admittedly less of a need but it still creates a better connection.
Robin Whitfield - the company that I’m employed by has over fifty years experience of using stranded tinned copper wire terminating in screw terminal block / choc blocks that have wire protectors. Our failure rate on these is extremely small and we have millions of terminals.
Why does the insulation check on the secondary pass when it's center tap is supposed to be connected to earth?
Because the test is DC and it can't pass through the primary coil - which it would need to to in order to get from the plug to the 110v outlet
Fick dich - no, because the DC test current should flow from the mains plug earth terminal to the transformer mid tap, through the copper winding of the secondary and to the output terminal on the 110V socket.
On all the 110V CTE (55V - 0 - 55V) portable or fixed transformers that I have encountered, the transformer secondary mid tap is connected to earth. So a multimeter on the resistance range should show continuity between either of the 55V line output socket terminals and any earth connection (be it the output earth terminal or the mains input earth).
Why not put a squirt of hot melt glue or a small rubber bung in that screw hole next to the gland nut to prevent water ingress in the rain or if the transformer ends up in a puddle?
Really great vid JW. Came here trying to work out whether there was a standard for the non earth pins in the 110v socket. No clues from the wiring seen in this video. Is there a live or neutral after the step down in the induced coil. Grey doesnt really provide much of a clue.
There's no standard for "polarity" here, it's split phase and simply doesn't matter.
question , can you use these transformers as a voltage converter for US appliances in the UK ? given that the continues rating is lower than the rating of the transformer
Yes, although it won't convert frequency so is of no use if something requires 60Hz.
One the last part of the test you meggered between earth pin on 13a plug and 110v and got 500megs but you should have got near zoro because th e secondary has an earth on it.
Yes I noticed that too I'm not sure whether the earth is connected to the centre tap which it certainly should be
@@dkek383 it's supposed to be earthed to comply with regulations.
The insulation test is DC. DC does not go through a transformer. Insulation test was between the 13A pug (primary winding) and the output earth (secondary winding). If he'd tested between the output connections and output earth then the insulation would be almost zero.
john flower - on all the 110V CTE (55V - 0 - 55V) portable or fixed transformers that I have encountered, the transformer secondary mid tap is connected to earth. So a multimeter on the resistance range should show continuity between either of the 55V line output socket terminals and any earth connection (be it the output earth terminal or the mains input earth).
Weeble Wobble - no, because the DC test current should flow from the mains plug earth terminal to the transformer mid tap, through the copper winding of the secondary and to the output terminal on the 110V socket.
So you just left a hole from the old screw open ??? so now damp can get inside through the hole ?? Also, was the brown leather tool wallet a BT phone engineers one ? I would have thought the internal earth connection would have been a Crimp Connection ? If it did have sand in it originally, then im guessing it would be for thermal reasons as well as damping the hum from the transformer ?
Good video JW. Any reason why you didn't fold the neg and earth over before putting into the choc block?
That’s only a good idea if your choc block is too big for your cable size. It doesn’t add any mechanical strength, except by filling up the hole a bit more.
@@JasperJanssen Whilst I appreciate your response. Singles can and will slide down the side of the thread of the screw and have floating wires in the terminal block. You're also less likely to cause crush damage to the wires with them folded - Especially when using flex. Good practice imo.
They weren't folded over originally, and it's lasted for 15+ years like that from the factory. The wires are large relative to the terminal block size.
@@mernok2001 Hahah, afraid so slip of the tongue.
Hi John ,
Great Video , can you draw a wiring diagram of the site transformer and show how the center tap works? I'm just curious to know how the voltage is being divided
Covered in this video ruclips.net/video/fRhofcMyAyk/видео.html
Top job JW, nice vid. I do have a question though. What type of plug goes to the output? It looks like a pin and sleeve connector.....
One of these: www.toolstation.com/industrial-connectors-ip44/p35522
Handy video thanks JW.
If you put the cable gland back to front ( opposite way to the way it was designed ) where is the protection to the flexible cable
If you knew how a cable gland works, you wouldn't ask. When used the "normal way" there is a round gripping clamp that squeezes into the outer sheath. That thing is right at the end of the domed clamp nut, and it is quite sharp.
So, flexing of the cable is pushing it against that sharp edge inside the end of the gland. By reversing the gland, there ends up being a rounded edge plus the sharp thing is nowhere near the flexing point.
Bottom line = the protection is BETTER with the gland reversed.
Many years ago I had to take a van load of this type of transformer back to their manufacturer to have their earths modified so that they could be used in telephone exchanges. Never could get any info on why, possibly something to do with earth potentials with GPO/BT systems. Any ideas?
Probably due to noise problems being introduced when devices where being used. Old BT Party lines used an earth but different system is used today.
A stupid question, but looking inside of that it looks as though it is earthed to the neutral.
Am I correct in thinking that or have I just seen it wrong?
Earth & neutral are separate.
Your videos are so so good to learn could you please videos on charger and power tools batteries?
Thanks
My father,while recovering a stolen car from a construction site that was finishing up noticed that they were literally about to throw about 20 brand new ones of those into a skip,he bought them home and they just sat in our garage for 20 odd years before he gave them to a scrap man😄.
If you don't mind me asking, is the 110 volt coming out of this transformer, AC or DC current? Sorry about the ridiculous question!
Thank you very much for uploading this video.
Kind regards, Dan George
It's AC.
@@jwflame Thank you very much for your swift reply! Kind regards, George
JW, TUT TUT. The stranded should have had bootlace ferrules!
If this was for site use I'm sure he'd have done just that ;)
I’ve never seen one like that, all mine the whole enclosure is filled with resin up to the connectors.
I have the same model as this, they are very common, and it is the same inside.
I have a site transformer that I use at home with 110 tools but it keeps tripping the earth leakage, mostly on turning it off but occasionally when turning on. Does not appear to be any fault with the transformer, could the secondary be unbalanced?
It may be the RCD - some can be tripped by sudden large surges, or the large voltage spike when it is turned off.
Quite common for the inrush current to trip domestic RCD's especially the higher current 3kW versions
@@jwflame I will get that checked again, the wiring in the garage where I use the transformer was only installed two months ago, and last night the transformer tripped the 32 amp ring main breaker instead of the earth leakage. I think that they might have used the wrong grade of breakers despite being told that I was going to be running welders and other equipment in there I have a 32 amp socket on a seperate breaker for the welder they installed so they obvious ly understood what was required.
It could also be that you have a fault between ground an neutral on *another* circuit. That will cause RCD to trip when starting any heavy load.
@@mernok2001 say you have two fuses connected to an RCD. There is a small leakage or short between ground and live on fuse 1. You connect a big load on fuse 2, a small portion of the current going back through neutral on fuse 2 will go out through neutral on fuse 1 and from there to ground. Thereby tripping the RCD.
Would these need a soft starter ?
The sand could be for spark arest in case of transformer failure like the ceramic fuses that are high energy ones
Can't believe he didn't know how the original cable grip works, trying to pull the cable outwards tightens the gripper, once the screw is loosened simply push the cable inwards and the insert comes out, LOL!!!🖖😁
Any body know how long ago we started using 110 volts on UK construction sites? Where did the idea come from?
after a bit of searching answered my own question
The system has its origins in the 1949 Annual Report of HM Chief Inspector of Factories, which recommended the system for use on building and construction sites and other applications involving large-scale use of portable electric tools. The system was described in the British Standard Code of Practice, CP 1017:1969, Distribution of Electricity on Construction and Building Sites (superseded by BS 7375:1991, now BS 7375:2010). Equipment was specified in BS 4363:1969 Specification for Distribution Assemblies for Electricity Supplies for Construction and Building Sites (now BS 4363:1998+A1:2013, also BS EN 61439-4:2013).
referenced from IET autum 2016
Roly M
Early ones had Reyrolle BS 196:1961 5 and/or 15 A outlets which were also yellow, but the casing was metal rather than plastic and I think painted with Hammerite; certainly the whole thing wasn’t yellow.
I’m surprised how small the actual transformer is for 3 kVA, but I suppose that’s only a tool rating. What is the rating for continuous loads such as site lighting?
@@srfurley ive still got one of those early metal ones.
Only a single outlet though and its taller, but still wotks.
Sand was likely in a bag that got torn. It would be ballast to add additional weight to the unit so that it won't tip as easy.
Thanks John - can these be converted to make an isolation transformer?
In theory yes - the earth connection to the secondary needs to be accessible so that it can be removed. Voltage output is still 110V however, so not really of much use.
you could make a pretty good step down transformer for travel purposes. if you're visiting the UK/Europe from the states. But due to the high in duction of first plugging in the transformer of that size, it be more practical in theory.
Thanks @@jwflame
Jonathan Furtado - eh? It is a step down transformer! You can connect most electrical items from the U.S.A. (or any other country that uses 110V/115V/120V) to these transformers. The only limitations are the rated power of the item has to be no greater than the rating of transformer (keeping in mind that these transformers are often tool rated, the continuous rating is lower) and any device that needs the supply to actually be 60Hz (clock/timer) will run slow.
JW referring to your reply, if you were really desperate, or bored, you could get a second tranny and fix 110V O/P of first tranny to 110V O/P of second tranny which will act as a step up giving you 230V. I can't think why on earth you would want to do such a thing in real life but it's possible
Very interesting video!
Love your videos John - looking at most modern fixed 13 amp fixed plugs and the pins are made of metal rather than brass - is there any advantage of having brass pins on plugs ?
Brass is lower resistance. I think the silver colour of the pins on some plugs is chrome plating.
Brass is a better choice for it's electrical properties, but other metals are cheaper and cost usually wins.
John Ward cheers John for the information
John Harwood - silver can tarnish 🙁
Can u cut the plugs of 110 power tools and put a 3 pin plug on them
NO. A 110volt tool connected to a United Kingdom 230volt 3 pin socket will blow the 13amp fuse. This is because a 110volt tool has a lower resistance than a 230volt tool and as a consequence will pass too much current. Should some idiot replace the 13amp fuse in the 3 pin plug then the tool will burn out.
So is this a step down transformer ? Not an earth isolating transformer ? (earth wires to the out put sockets, scares me)
A little squirt of wd40 in the plug holes is always a welcome treat for the user... as these 110 plugs can be tighter than a ducks doo daa at times. 👍
like getting a marsh mallow up a wild cats arse, in reverse
I love them cable grips (the one you threw away), when the screw is removed, the rear insert comes out, releasing the mains lead. (I noticed a bit of sand in it, so pliers might be useful). I use them on my reel to reels.
+1, we used them on our fan heaters etc, at Rima Electric (taken over by Sunbeam Electric).
I would have used a new flex cable. That one has obviously failed due to age. Plus I would also add a nice power switch.
It’s failed due to repeated stress at a particular point. Not at all due to age. And it shouldn’t have a power switch.
@@JasperJanssen I recognized the cracking on the jacket. The rubber, or whatever it's made of, has deteriorated and had begun to crack. It was just accelerated at the joint because of stress. In less than 5 years you'll see a repeat failure and the rest of the cord will show its true condition. Having a nice emergency off switch can't be a bad thing.
You would need a power switch to have the same IP rating as the transformer pot and then there something else to get broken during use. ,
Why the resistance between the incoming ground and L or N on the output is >500 MOhm at ruclips.net/video/2t_JR0CxctQ/видео.html ? I thought this is a center tap transformer with the center connected to the incoming ground as it on this wiring here ruclips.net/video/fRhofcMyAyk/видео.html
Hello sir, can these transformers be used to power audio equipment as is? I am assuming the center tapped ground would cause grounding loop issues, especially if using audio equipment in conjunction with other equipment connected to the 240v mains.
That terminal block doesn't look original.
Great video JW. Maybe should’ve used ferrules on the neutral & CPC connections though.
Not really, as you are going from a flexible cable to a solid core. Should have a fixed terminal on the case so any flexing of the input wire does not stress the solid wire and fatigue it. The solid wire is the transformer primary, and if you break it off at the most common point, the place where it goes into the potting, you now have a very heavy paperweight. Ferrules on the CPC however are fine, they are both flexible cables. John should have taken some sandpaper to the top epoxy to clean a spot, then used solvent to degrease the spot before putting on a cable tie base and 3M VHB foam to hold the base, then a cable tie to hold the floating connector block to the top there. Less stress on the solid wires.
The original gland is easy to take apart, just push the wedge back out the back, or use the cable stub to pull it out, and then reuse it again. Those glands are quite strong, you can easily hang the transformer on it with no problems, the cable will break before the gland lets go.
Cable is a silicone rubber cable, rated for use in Arctic conditions, and also rated for use in water, so it is waterproof and still flexible at -55C, and can be used up to 130C. You normally find it used on pond pumps, and I have made quite a few extension cords out of them when the pump fails, or if, as I was doing, I only needed a 50cm tail on the cable, and the pumps come standard with 10m.
BS 7671 Regulation 526.9.1 In order to avoid inappropriate separation or spreading of individual wires of multiwire, fine wire or very fine wire conductors, suitable terminals shall be used or the conductor ends shall be suitably treated.
@@garymckeown4278 common c2 on my eicrs where people shorten rcbo neutrals and just twist. No amount of tightening will guarantee a solid connection.
thomas bourne yep and on my last NICEIC assessment this was mentioned by the assessor.
@@garymckeown4278 as an apprentice I was taught to twist and double but that was through lack of knowledge and the fact it takes longer but once you know it's wrong why would anyone continue to do it. It doesn't make you popular when you fail entire marinas where the pontoons are all wired in h07-rnf without a single boot lace ferrule in sight when the client has only recently rewired it.
Is this the preview to the movie sequel being released next weekend?
Transformers, the battle of JW .
What's the purpose of the sand filling?
Cooling, Many of the users of these transformers would have them supplying 110v volts for a large amount of time during the work day. The sand would reduce the chances of the transformer overheating but it also would make it heavy, maybe they deliberatley removed the sand to make it lighter.
Why not transformer oil. That would be a better coolant than sand.
@@simontay4851It's done for stability, to stop it being knocked over, nothing to do with cooling
What kind of 110 sockets are those? They aren't like our North American ones.
www.toolstation.com/industrial-connectors-ip44/p35522
Known as CEE form colour coded yellow for 110 blue for 240 and red for 415
@@jwflame Oh, nice. Those appear to be very well designed.
Those are known by several common names, the correct designation is IEC 60309, it is now an international standard for "industrial connectors". They are strongly color coded for voltage and have the earth/ground pin in a different "Clock position" based on that voltage color correlation. The ones in the video are IEC 60309 4h 16/20a. Common colors are Yellow for 100 ~130 VAC, Blue for 200 ~ 250 VAC, Red for 400 ~ 480 VAC (230/400 Three phase being most common for red), There are several less common colors but one in particular that may be of interest to you is Orange, Orange is only found in areas that use split single phase that wish to distribute to the end point at 120/240... that would be North America. Orange came about as part of series 2 certification for IEC 60309 plug and socket type pin & sleeve devices for use in North America. You can get these in North America but their use has primarily been industrial, but are gaining traction as replacements where proprietary pin & sleeve designs were already popular. Most smaller North American domestic sockets (NEMA) are just that, for domestic use, but in general are absolute garbage in the shop, do they work yes... are they going to survive being stepped on... well once or twice. A 60309 takes allot of abuse, I actually use these on all my portable power tools, and since I attempt to only buy 50/60hz small tools, I can use them anywhere in the world with a proper local adapter and/or transformer. Wikipedia has a nice table of voltages and configurations which offers a basic introduction to the system. en.wikipedia.org/wiki/IEC_60309 Edit: P.S. In North America they seem to be ridiculously expensive, but can be had cheaply if you keep a watch, I have boxes upon boxes of them I've picked up for reasonable prices, so I always have them at hand when I want one.. they really are superb.
what name did you say on the intro? Didnt sound like john ward
It's his real name, Jay DubbleVue
He says his initals J.W., even though that has more syllables than his full name :)
@@Petertronic Missed that. thanks
Why don't they omit the centre tap so it just becomes a isolation transformer?
Because then it would just be an isolation transformer, this is a site transformer - in which the whole point is to give it a centre tap. Though you can omit the extra earth connection yourself on some of these transformers if you so desire
Because then a short between primary and secondary in the transformer would not blow a fuse and would make the secondary side live at up to 1.5 times mains voltage relative to Earth.
@@petehiggins33 That's not true, omitting the centre tap doesn't make much difference it just makes the output 0v - 110v rather than 55v - 0v - 55v.
The primary and secondary core cannot short together because they are only connected via a magnetic coupling not an electrical one - even so the power is supposed to flux between the primary and secondary coils to make it work anyhow
Ben Vahanian - because the whole point is to keep the voltage of any accidentally exposed conductor as low as possible. In a damp or wet construction site environment, it may be troublesome to maintain the system to be earth free. And the system would have to undergo regular testing to find out or confirm if it is earth free. By earth free, I mean all the 110V supply equipment, all the extension leads, all the tools etc. would have to have absolutely no insulation faults. It all would have to be tested with a insulation tester. This is not very practical.
Why? Well if any of the conductors suffered an insulation fault (say a cable snagged on a piece of metal that was lying on the ground), your isolated earth free 110V system would now be an earthed 110V system. If a second fault was to occur, say a worker damaged the flex going to a power tool they were using, but did not notice. And then later on accidentally made contact with the conductor. If this was the now ‘hot’ conductor, they would complete the 110V circuit to earth/ground and could receive an 110V electric shock which could electrocute them.
Even if no second fault occurred, it would fail the next insulation test. Bringing the job to a halt.
Hence the solution is to centre tap the secondary winding of the transformer. Now by having an intentional proper earth, if either of the hot lines becomes earthy due to an insulation fault and a high fault current flows, the overload device will trip. Even if no significant fault current flows, if a worker accidentally makes contact with either one of the conductors, the maximum voltage that they would experience would be 55V. It is unlikely that this voltage will cause them injury. Hence this is the safest system.
C'mon John. You know it's not 230V and 400V. You know they haven't changed the taps on the transformers.
Test your own input and do a video to showing what your voltage is.
Voltage here is about 250V. You are right in that the actual voltage hasn't changed in most places, but the declared voltage is 230V, and 230 is what's used for calculations, even though the actual voltage isn't usually 230V in reality.
Do you know what they *actually* changed the nominal voltage to? Here in Australia, a couple of years ago the area I live went from 240V +/- 6% to 230V +10%/-6%, which means the maximum allowed mains voltage dropped from 254.4V down to 253V. So in other words, the nominal voltage went to 230V but they didn't have to change any taps on the transformers...
Although in our case they actually had a sensible reason for making this change. It seems there were so many grid-tied solar systems being installed that it was pushing the voltage too close to the limit, so by lowering the nominal voltage to 230V it means they can slowly go around changing the taps in areas that feed in a lot of solar power, and they don't have to worry about the voltage dropping below the spec on cloudy days when nobody is feeding in.
Well, when I do my calculations I use the voltage at the job n use that instead of the stated voltage thats in the regs.
@@Berkeloid0 Same here, 230V with allowed range 216 - 253.
@@jwflame madness ain't it 🤦🏻♂️
Center-tapped 110V? That's rather odd.
What are those sockets? They don't look like US plugs would fit, which is what I'd expect on a 110V power tool. I didn't think 110-120V service was commonly used outside North America.
The problem with reversing the cable gland is that the gripping fingers are directional. I'm surprised you don't have step bits for conduit sizes.
Nylocks are a good choice, but I would probably go for blue Loctite (242). One bottle fits all screws.
It's a weird British thing, for safety purposes. These are used on construction sites, where there's a lot of potential to contact live wires while grounded. They have special tools as well, designed to work on 110v 50hz current (here in the US, it's 60hz, so our tools would theoretically work fine on one of these transformers, just slower.) The transformer is connected similar to our 240v appliances- the outside transformer in the US supplies 240v, with a center tapped neutral that is referenced to ground. In this case, it's a center tapped 110v transformer, with the center tap referenced to ground. That way, if a worker comes in contact with a live wire, it's at most 55v to ground, which is much less likely to cause injury or death. As for the different plugs, there's lots of different standards. Something similar to ours are used in China, but on 240v.
puckcat22679 - most electric drills used in most tools are actually DC motors fed via rectifier diodes. So these would not care if the supply was 50Hz or 60Hz. Secondly, not all AC motors care much about the mains frequency, as long as it is in the correct range. So again there would be no significant speed difference.
The connectors are actually an international standard, look up IEC 60309
As usual with site transformer it has been fixed at least once before._
What's unusual is that the fix has not been a complete disaster waiting to happen and burn the house down :-)
@@benbaselet2026 Yeah, someone must have known what he's doing._
what make/model is the cable crimp tool used at 12:30? it looks really good with that ratchet action.
It's CK, not sure of the model number. www.ck-tools.com/products/ck_tools/pliers_cutters/ratchet_crimping_pliers/
keep considering putting a zero crossing relay on my transformer, only really an issue in house were you cant trip the board
Actually almost the worst you can do, as then there is no remnant field from the previous half cycle to provide back EMF. With these a much better protection is an appropriately sized NTC inrush limiting resistor, and for larger loads you then also have a relay and time delay ( around 5 mains cycles) after power on that then shorts out the resistor. That provides enough impedance to reduce the start up surge, and still allows protection devices like fuses to act in case of a shorted output properly.
I have a 2kVA variac that I did that to to reduce the inrush surge to a low enough level that it would not trip the 30A breaker it was attached to, and also not trip RCD breakers.
Actually zero crossing gives the wort case surge with a transformer. The reason is that when a transformer is running open circuit, being an inductor, the current lags behind the voltage by 90°. So normally when the voltage is crossing zero, the current is at its maximum reverse polarity and over the next half cycle of voltage it goes though zero and then to its maximum positive value.
If the current starts at zero then over the first half cycle it will rise to twice its normal value. That would not be too bad except for the fact that transformers usually run with their core close to magnetic saturation for efficiency reasons. That means the core saturates during start-up. The inductance disappears and then the only thing limiting the current is the DC resistance of the primary, so the current can be enormous.
Counter intuitively, the best time to turn a transformer on is when the mains is at its peak voltage.
With the transformer primary uninsulated wires flapping around and having the potential to touch each other (but probably not), I would have been tempted to fasten them down or put some insulation over at least one of them just to be on the safe side.
Those wires are enamelled copper, not bare.
Yup, enamelled wire. But I'd still have been tempted to add some sleeving :-)
Also I'd have used a 3-way choc block, LEN, so any future flex cable change didn't need a re-crimp; and glued or bolted it down, to avoid any wiggling of the transformer wires... :-)
Yep I know but enamelled can crack and ware off when things are touching and not fastened down. Put it like this, I would not risk holding an enamelled wire that was live if it had been able to move around freely. Not even sure I would want to anyway. In the transformer the windings you essentially have double the insulation between the windings and they are fixed and still. No cracking, flaking in the enamel should occur when totally still. But the wires are out in the open and can flex/move a bit, all bets are off (in my opinion).
What about the screw hole you left why not make the hole just go to that screw hole
My builder neighbor has one of these, it looks like its been dragged through a war zone.
It has, that's what building sites are. 😉
nothing wrong with the cable grip you removed it on a taper which is tightened by the screw
This has to be one of the oddest aspects of UK electrical code, to me.
We don't collect manky old screws:JW 2019 😂
This is a typically convoluted and cumbersome British "solution" to a fairly trivial problem.
Use a huge heavy transformer box with huge inrush that trips normal circuit breakers, so site must provide special outlets and wiring. Requires all tradespeople to buy a second set of tools with US plugs that operate on 110V. Giant box contains no short circuit protection, so shorts to ground or between "Lines" will cause big current and unsafe fault on the tools' cable. No switches on the 2 outlets.
Elsewhere in the world we use a 220/240V unit with standard sockets, so normal tools can be used. Inbuilt RCD protects operators against shorts to ground. Inbuilt short circuit protection protects the gadget and wiring. 4 individually switched outlets, 10A or 15A. Light weight and low cost.
Example: www.gettoolsdirect.com.au/portable-power-board-4-way-15amp-outlet-pp015t.html
It's really not that bad.
Consruction sites have 110V power from dedicated transformers, such as www.blakley.co.uk/products/transformers/site-transformers-4kva-to-20kva/site-power-transformers/tap320s12
all of which have circuit breakers on the outputs to disconnect if short circuits or overloads occur.
All tools and lighting on construction sites are 110V, and if people want to use those tools elsewhere they have a small transformer such as the one in this video. No one buys 2 sets of tools.
They don't have those dreadful flimsy US plugs either.
RCDs and 230V can in theory be used, but they never are. 110V with 55V to ground is reliable and safe. RCDs need to be tested often and would be quickly damaged/destroyed on a typical construction site, which in the UK will frequently be soaking wet.
1. That remaining blue crimp doesn't look like its been completely squeezed down properly. The open end is still circular.
2. I would have added sleeving to those two bare copper wires so that cannot directly touch each other.
3. I would have added a neon indicator to show when it has power.
The copper wires are the ends of the transformer windings so they are already insulated
NO! You don't put the old bolts and nuts in the bin! Even though there are only 3, not 4, you can keep them to reuse for a future project. Same with the original cable grip. There must be a way to open it to remove the damaged piece of cable and put the good cable through. Also you can reuse the original spade connector. put a piece of heatshrink tube over the incoming wire, strip and solder the wire to the short piece of wire still on the spade connector, slide the heatshrink tube back over the solder joint and shrink it. RECYCLE the copper from the damaged piece of cable.
Simon Tay weapon
He had a whole unsused pack of nuts and bolts. Why keep the old ones. Also reuse old spade connectors? Just NO
Solder wires to the stub on the spade connector? Please don't. The price of a spade connector is not worth the time or effort of bodging it back on, not to mention that it looks incredibly unprofessional. Have some pride in your work, and people will respect you for it. Doing poor work in order to save a few pennies does NOT look good!
only thing i would have done is ferrule the ends of cpc and neutral
(9:45) - *_Not that this should of course be outside where there's water..??_*
Excuse me but aren't they designed to be used on building sites?
Like, building sites that are open to the elements?
Sorry John but I have to disagree.
These transformers are very much designed to work outside.
Under the pouring rain.
And I don't think I'm wrong here.
>
This one is a portable transformer designed to be located indoors, and 110V items attached to it for use outside. Larger building sites would have a much bigger transformer with multiple outlets, located in a single location away from where the tools and other items are being used.
The point is to keep the 240V away from the work area, otherwise there isn't any point in using 110V tools.
Using a portable transformer with a 240V extension lead and standing next to the transformer outside with a tool connected on a short lead is totally the wrong way to use it.
would have been easier to re use the existing cable grip rather than have to enlarge the hole to use a stuffing gland and cable tie.
Yee, exactly. And he should have done.
It’s just a wedge grip, push the wedge out and reuse it.
Wow. It wasn't exactly a difficult or time consuming job though, was it? It's not like it took him several extra hours of unnecessary work. If he prefers the new one that's up to him.
I searched Megan Fox and got this
whats that funny writing on the lid ?? "UK MADE" what does that mean ????
UK = United Kingdom / made in the United Kingdom
55 VAC RMS to Ground is almost 78VAC Peak to ground
And the peak to peak voltage of a 240V AC RMS supply to ground is 340V. Which would you prefer?
Frequently these transformers are potted in solid resin and not easily dismantled
Whose on first ?
Please do not hit things with the palm of your hand, you have a whole lot of nerves running through there. Mess them up and your in trouble.
Other than that, thanks for the video.
ssshhhhhhh.
??55 110vac I think you mean
55-0-55, 55 volts to earth, 110 volts between the two conductors.
ed riley throbber
Most houses today in the US have two 110 volt wires and one neutral wire running into the house from the local distribution system. These wires can run underground or above ground. If there are two 110 volt wires running to the house, then the house has 220 volt service and appliances, such as dryers and air conditioners.
Back under your bridge Troll.
The supply flex will be HO7RNF or HO5RNF 😆
were is the repair ?? replacing jumper wire does not repair anything :D