Isolation Transformers can save your life, and your equipment.
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- Опубликовано: 10 фев 2017
- tvrepairinfo.com
I discovered their importance of Isolation Transformers in the school of hard knocks. At that time of this educational experience I had just started working as an apprentice in a television repair shop, and my boss asked me to hook up a our oscilloscope to a TV he was repairing. The moment I attached our oscilloscopes ground wire to the TVs hot chassis I saw a bright flash of light as the TVs fuse blew, and noticed the TV we were repairing was now in worse shape than when it came in. Fortunately my boss allowed me to make a few mistakes, and after this experience I learned why using an Isolation Transformer can be so important.
Thanks to a viewer I was informed that some of the new isolation transformers which use a ground port may not isolated. I suggest you look at this video link by a youtuber named old goat who explains this problem on some of the newer isolation transformers at • ISOLATION Transformer ... . Another good one by Mr Carlson's Lab for further reasons as to why this is. • Tech Tips Tuesday, Iso...
This is not just the best explanation but the way it has been done with sketches on paper and placing one sketch over another is an ingenious technique that eliminates computer graphics and all explanations can be done in an old school way. Teachers should note this point!!
computer graphics can be a waste of time if it's something simple like this
Back in 1988 the workshop I apprenticed in had an isolation transformer at every workbench, and we always plugged the item under repair into those sockets as they were the only ones available. Made life a lot safer.
this is great great explanation like me who don't know anything about electricity . thank you
This is great. I did not appreciate the importance of an isolation transformer. I see now it's all about eliminating the ground reference (which one might be standing on). Great stuff, thanks.
I had a few times I got shocked I got nailed by 440 dc while on submarines which I spent 7 years on . It was built in the late 60 s It has a floating ground so when I was using a o scope across it with out an isolation it blew up the scope and me . Believe it or not the NAVY test for using back then was to remove the ground off the o- scope I also got nailed while working on a generator outside in a storm I was about 100 feet from a lightning strike and the voltage went across my chest and come out my hand . I was blind for 4 days and still have the scars today .I was lucky to have the guy working knew how to use a resuscitate kit.
The simplest and most effective explanation of this concept.
Great video!
Thank you
Nice job man today only I came know about the application of isolation transformer and I want to appreciate that you are well experienced one in this field.
Good video.... Made me remember what Einstein told once " if u cant explain it simply, u don't understand it well enough"
Good effort....!!!
I love your drawing!!! Great job explaining the isolation transformer.
Words to continue living by, my friend. Thanks for the info.
Three reasons to use: Prevents electric shock (ground islation), suppress electrical noise in sensitive devices, and transfer power between two circuits.
Very well explained, thank you and congratulations. Also the sound quality is very, very clear, and without background noises, hums or anything disturbing, it's all cristal clear. Great job!, and thanks for making this second improved video about this important subject.
Thanks for the comment.
Great job! Thank you! finally someone explained this without getting lost in details..
The best video description I have ever heard of isolation transformers usage.
Thank you
one of the best videos and explanation with the real problem.
I have faced the same issue but unable to find.thanks for uploading the vidoes.
The thing with some newer isolation transformers is that the neutral is connected to ground. The little adapter you had there won't prevent a hot chassis as long as the neutral is still connected to ground. You have to physically disconnect the wire that links the neutral line to ground in order to float the output.
Having a ground connected to the floating secondary side of the transformer voids the whole principle of the isolation transformer itself. Especially if it's connected to neutral, don't you have earth leakage differential breakers where you live?
Very clear explanation. Thank you.
Thank you, very clear explaination!
Balanced isolation transformers, which are popular for line noise filtration for audiophile and home theater equipment, usually have a center-tap on the secondary which is connected to the ground contact of the outlet and even the case. That has to be disconnected to use on the test bench. Otherwise there's still a DC path to ground from ground and both legs on the output.
Great explanation. I like the way on the drawing the sockets appear to have face and be horrified at the shock they are unleashing. At least that is what I saw... Thanks for sharing.
Thanks for the feedback. I'm glad my fine art is appreciated. LOL
@@GrantsPassTVRepair Well when it is something worth remembering then in all seriousness actually it is very effective teaching mechanism. Thanks
WoW. Best & easy tutorial on RUclips regarding isolation transformer.. You should be a lecturer for electrical engineering not just a tv technician.. Keep it up..
Thanks Sir, it is very helpful to me, thanks for sharing 👍
One of the best videos on isolation transformer
Thank you.
There are many videos on RUclips about the purpose of an isolation transformer. This one is the clearest and most accurate. However, there is a brief reference to "having the oscilloscope connected to the isolation transformer". That is not a good procedure. Instead, connect the device under test (DUT) to the isolation transformer.
Thanks. That's the kind of comment I like to hear. Keeping it simple is a big part of my thinking when I make a video.
Just one other point: While the "earth" path does provide some (undesired) conductivity (as shown in your diagram), the ground wire running from the third prong back to the circuit breaker panel is the primary path of (undesired) conductivity. The "earth", the third prong, and the neutral are, of course, bonded together at the service breaker panel as required by the NEC. The key point to understand about a "tech" isolation transformer it is that is breaks the bond between the neutral and the ground conductor (and earth).
However, you can inadvertently reestablish the bond between neutral and ground by plugging a three-wire device into an a "boxed" isolation transformer because the input mains ground and the output mains ground are bonded together, even in a "tech" isolation transformer. That's why you also need the three-prong cheater plug when plugging a three-wire device into an isolation transformer, as explained starting at 4:58 in the video.
I wish to demonstrate noise on an AC main displayed on an oscilloscope, how will I do that safely if do not connect the isolation transformer to the scope?
Fully agree
When I wired houses, and installed the plugs during the trim, we always hooked the hot to the gold side, and the neutral to the silver. Yet, you are correct, that some people must be color blind!
Very easy to understand. Thanks!
i dont mean to be so offtopic but does any of you know of a method to get back into an instagram account..?
I somehow lost the login password. I appreciate any tricks you can offer me.
@Cannon Jabari Instablaster =)
Nicely explained.
I picked up a used Tenma 72-1095 Isolation transformer and variac combo unit a while back. It's a nice unit and can handle up to 3 amps but the funny thing is that it still has a feed through safety ground (the output ground is bonded to the input ground) even though it is a "tech" isolation transformer. I ended up modifying it and putting a toggle switch in to make the whole thing either floating or grounded depending on what I'm doing. Just goes to show now matter what you buy, always check the grounds.
Hopefully others who buy them figure this out like yourself.
Why would you need to have earth linked between input and output as it loses the whole point of being an isolation transformer? I'm sure I'm missing another sort of application here
@@santoelectron US regulations and electrical code. Devices sold in the US especially with a metal chassis and mains powered must be earthed. You just have to modify it when you buy one.
nice job as always, very good content
Clear explanation. Thanks!
great explanation thanks
The item of special note is that the earth ground is no longer present on the secondary output meaning the ground port in the secondary outlet is floating. This is important with the reason being that a device under test could have its own neutral to ground union that you are not aware of. That being the case would be similar to the neutral of the secondary windings being grounded, just in a different place.
I liked that, he gets right to the point, no gobbledygook.
Great Video!
Thanks for sharing
You rock man the minimum thing I could to was to subscribe . Thank you
As far as "hot chassis" a lot of older equipment had non-polarized plugs. Sometimes you could eliminate the hot chassis simply by flipping the plug over, or outfitting the device with a polarized plug with the neutral connected to the chassis instead.
Ryan Toomey true but that doesnt solve the isolation issue. But does make it safer.
Very easy to understand. Thanks!( best of all )
Thanks for the comment. I also have a follow up video on this topic you may find helpful at ruclips.net/video/M2v04tdp5B8/видео.html
Also to mention, that a isolation transformer doesn't have a neutral on the output, but has in fact 2 lines (hot) wires, with 110/120V or 220/240V between them,
and a ghost / phantom voltage between one of these 2 and the real earth.
Another note is that the RCD in the breakerbox doesn't trip, when you touch one of the 2 line wires of the output of the isolation transformer.
Adding a RCD at the output of a isolation transformer doesn't work either, because a RCD won't work with 2 hot wires, and needs a neutral.
To create a neutral on the output of the isolation transformer, you must bound one of the 2 hot wires to ground/earth,
that one becomes the neutral now, the other wire stays the line (hot) wire.
The RCD will then work, but you loose the benefit of the isolation between the hot and ground reference.
At the end, it is a choice to make between protection against electrocution by using a RCD, or protecting the oscilloscope by isolating the DUT (Device Under Test).
There is a sort like RCD device that works with networks without ground, and its called a "Isolation Monitor Relay", but is very expensive and used in industrial sites.
Thank you for this information.
No no no! The output is isolated. You will not get shocked by either of the wires as the output is not grounded. You must never ground the output of an isolating transformer. You will defeat the purpose and create a death trap.
An RCD will not work as it is it possible to have a ground fault as it is not grounded. An RCD does not need a neutral. It just needs a grounded (not to be confused with earthing) system. If could be midpoint grounded like US 240 V or British 110 V construction site voltage. Those both have two hots (unlike the output of the isolation transformer) and an RCD works. Isolation is a far better safety system than an RCD.
Note that you can still get shocked if you touch both of the outputs. Then you will complete the circuit and the shock is as bad as any mains voltage shock.
@@okaro6595 i'm aware that grounding a isolation transformer defeat the purpose of a isolation transformer.
But later i found that there is a way of using a RCD in combination with a isolation transformer and have a mix of both worlds.
If you tie 1wire of the secundary side of isolation transformer to the earth pin of the isolation transformer outlet socket, and from this connection a 1M 3Watt resistor to the earth of the wall outlet, then this connection becomes a neutral. The 3Watt is for the voltage rating.
This way you have a high impedance earth connection from isolation transformer output to ground, and you have a low impedance connection between the earthpin of the isolation transformers output and the second live wire of the secundairy. With this configuration a RCD will trip if there is leakage from the second live wire of the output to chassis of the DUT.
Thank you.
very good i understand now now thanks alot
In my past work we have a lot of this device on test machine use the way. It also has a varistor on both side
That's a great idea! Btw...I never trust that the house outlets are wired properly. For less than $10 you can buy a little tester you plug into the outlet that tells you if it's wired properly. Love em!
@74dart man, you are so right! My sister and brother in-law bought a 40 year old trailer in Florida to winter in (so did I). I didn't like the way their breaker box was wired, and I have two year degree in industrial electronics, so we started testing all the outlets with one of those testers. We found about eight outlets wired backwards from the factory. So many were worn from use and we replaced about a dozen. Also, they had no lightning protection at the box and I added some.
@@ggsumner1947 that's awesome that you found that situation and fixed it. You can never be too safe with electricity!
good job simple explenation.
Well explained...
Thank you.
Killer bro thanks
Likely saved a life or two !
Thanks
very good explantion, I like it
useful information, thanks
Isolation transformers are also useful on audio equipment to eliminate ground loop. Much safer than using a three-prong to two-prong adapter.
I HAVE NEVER TRIED THAT ON MY AUDIO / GUITAR SYSTEMS THANK I WILL TRY THAT NEXT TIME I GET A HUM !!!!!!!!
So nice thanks
THAT DRAWING IS AWESOME
I must have missed my calling. I shoud have been an artist. LOL
I got super lucky with a tv the other day. Symptom was wiggle the cord, tv came on. Finally died. Was given to me to fix and I opened it up and the cord was fine. When I plugged it in it arced across the rectifier and polyfuse. Bent the leads and the damn thing worked. Free 2 minute fixes for a free 50 inch works for me. Glad I didn't need to pull out a scope, don't have an isolation transformer.
Good deal. Sometimes the repairs are quite simple.
thank you for your video
Thanks so much for this video. In a professional audio recording atmosphere, would you say this could be a possible solution for isolating specific pieces of gear on the same circuit (analog and digital) that may introduce a 60 cycle hum back into the shared power line?
im here for the same reason
Wow excellent ....🎉
Great explanation and visual the best I have seen on you tube bar none. Carlson labs has a vid on this but fails to explain that his iso transformer is NOT completely isolated (ground) and assumes that all are like this. Some iso transformers will have a 3rd ground plug in on the output just to conform with saftey requirements but do not make a connection to the chassis and are still isolated, therefore you have complete isolation. Contrary to Mr. Carlson the adapter is safe to make complete isolation if your transformer is not. Great vid again. Thanks.
Nothing like a hands on experiment to bring a little clarity. Thanks for the kind words.
I've been having trouble with my soundbar. Not one video on soundbars with buzzing/ static type noise. And also my tv speakers sound blown unyet I've always used the soundbar... now I have to figure out if this is fixable by getting this isolator thing for a coaxial or..
good info, liked
Thanks again for the youtube tips Mr Tampatec. They are much appreciated.
thanks for the video. i got bit by 220/240 at a job whilst moving a bandsaw. i had grabbed the leg of the saw that was the ground. my foreman saw what was going on and he came over , with one arm ,grabbed me . i think he could have been grabbed too.
Your blessed to have lived through it. I remember getting a couple big shocks as a kid, and how traumatic it was. A couple years ago one of my viewers got shocked while working on a TV, and he called me to ask if he was going to die. I couldn't help but laugh since he was on the phone with me after the fact, but at the same time I understood his concern since he had never experienced anything like it before.
Thank you!!!!!
thank you
Thank you for this. I survived some shocks. Will an isolation transformer work for guitar amps when probing voltages? For example taking live voltage readings for troubleshooting. Thanks.
This video is old, but just in case someone stumbles upon it, simply removing the ground prong puts you into a worse position then before, and having the transformer not being grounded at all is also dangerous, all you want is for the neutral and ground to not be bonded, not allowing that fault current to go through you on the secondary side(where you plug your device into). It still allows fault current from the primary side(where the transformer plugs into the wall) of the transformer to go through and trip breakers instead of blowing up.
grate video
Would you put that two-prong plug on the primary side to isolate primary from mains ground, or should it be installed on the secondary side to isolate it from ground in case the secondary and primary are both grounded to the transformer body.
Heck, I still remember getting zapped removing the CRT anode cap from a Symphonic 3" B&W TV that hadn't been powered up for over 15 years. "POP!" (Why does the stick man wear grounding shoes?)
I have heard of cases where large high voltage capacitors pick up static electricity just sitting on the shelf. I can see how the same could happen with a picture tube. I've been bit by charged picture tubes on numerous occasions. It puts a little spring in your step. :-)
Explanation very clear why it’s essential, but it’s the implementation that is super confusing. Some are saying disconnect the ground wire inside the IT and you’re good to go, others say oh no that’s not right, others just use a cheater 2 prong plug, others say no. I haven’t seen a single video yet on how to get this 100% safe and correct that all agree on. Really wanna get this right but it seems impossible as I’m just starting out. :(
Does anyone have an isolation meter scheme to suggest? Even if we use isolation troansformer to supply the dut, when we Connect first oscilloscope alligator clip, we cause a 1st failure to ground. If we connect the second one All is over.
Best and simplest explanation
Can you recommend a transformer please, maybe from Amazon?
Thank you for the explenation. Do you use a light bulb in serie + isolation trasnformer. Anyone???
Hai if i checked the supply with the tester is it works or not
Isolation causes problem only if you have to scope in the primary of the power supply and connect the ground clip to the minus of the filter capacitor.Otherwise the secondary windings are isolated from the mains also the metal parts and all the internal groundings too.But scoping to the primary side of a switching power supply is not very common and does not have to reveal useful information but mostly will cause an unwanted glorious blown with spark and fume residues.
How to measure the voltage output of insulated transformer?
I bought one of these transformers, the same one in your video but it has an extra little short white wire coming out of the back (same end that you plug into the wall) Do you know why that would be?
I had no idea. If you use an isolation transformer to power a ham radio, would it introduce noise or the opposite?
I recently purchased a isolation transformer on Ebay and even thought there is no continuity or resistance between the windings when i plug it in I get almost full line voltage appearing between the small prong and ground. My understanding is that this is caused by interwinding capacitance. Do I have that right and do I need to be concerned about it when connecting a bench scope to a hot chassis under test?
Sometimes a meter can pick up what I've heard some people call phantom voltage. Perhaps that's what you're talking about when you mentioned interwinding capacitance. If whatever you are measuring is just interwinding capacitance, it should not have enough power to operate a load such as a light bulb, so it might be interesting to place a 120 volt light across the two points you measured from, and see if there's enough power to operate the light.
Question. Their is continuity (4.5ohms resistance) between the hot and neutral tabs on my Iso transformer. When you plug it into a socket then everything on that outlets hot and neutral has continuity (4.5ohms resistance instead of an open loop). Does this matter? The iso transformer is like a big wire that connects Hot and neutral together. Thanks!
Sadly I just don't think that I can do this topic Justice in a RUclips comment. LOL inductors by Nature are bit more daunting because there is more for you to visualize about them. What I will say is that you are measuring DC resistance with your multimeter and that that is not taken into account an Incredibly crucial part of inductors called Reluctance.
Regardless though, I will say that you can probably safely visualize the power coming out of your Transformer as a push-pull type of arrangement. When power is going through the Transformer and a magnetic flux is being created, the power in The Wire is basically going to be following Lenz law. This means that the electricity is going to move in a specific Direction on one half of the sine wave and the opposite on the other half. The electricity that doesn't get used in this Arrangement just gets dumped back into the Transformer again as a magnetic flux.
I probably explained this badly and maybe even incorrectly. I would just recommend that you look at the excellent videos done by afrotechmods on the subject of inductors. There is also a good one from Great Scott and I believe a ridiculously in-depth one from mr. Carlson's lab.
the first man on youtube know what is LENZ LAW and MAGNETIC FLUX ,your are the man ,You must bee european because you know what i know.( may be same school )
Thank you for a clear and concise explanation. I am a little bewildered though ! I bought a new isolation transformer for my 14 year old son who is chasing a career in electrical engineering, and after I was wondering why he needs it. Sir in you case and with your explanation, I understand that. I live in a house with a RCD on every circuit. I can put a pin into any of my 240 vac outlets and the RCD will trip at 15 mA. In Australia, the neutral (common ground) is also tied to the local ground (stake), but if there is a differential between the neutral and the active, the RCD will trip at 15 mA. So for my son, isn't it better not using the isolation transformer ? With the isolations transformer,,, if he is working on 240 vac live and he accidentally touched active and neutral he could be dead, but without the isolation transformer, the RCD would trip... I have tested my 22 RCD;s in my home... I am curious,,, and always like your videos and respect your experiences. Cheers.
I'm not sure what an RDC is, but I'm guessing you are referring to a ground fault power outlet with a built in circuit breaker. Since the isolation transformer is preventing the ground fault device from being able to trigger at 15 MA, I understand how that could be a problem. It would seem that in such a circumstance you could be better off not using an isolation transformer, so long as your ground fault outlet is reliable. On the other hand keep in mind that using an isolation transformer doesn't mean you are protected from getting a deadly shock, it simply eliminates the possibility of being shocked between earth ground and one of your mains hot wires. I hope that makes sense.
@@GrantsPassTVRepair Yes, Sir it makes sense. A RCD stands for "residual current device " meaning if there is an imbalance between active an neutral greater than 15 mA it will trigger a circuit breaker,,, they are reliable, but should be tested monthly by pressing the test button which will trigger and shut off. I think from memory it is 30 m/s. They are mandatory in all new Australian homes. There are so many RUclips videos on isolation transformers, but I don't understand the need. So I am going to connect my scope the wrong way deliberately to see what will happen. I can only predict that the scope and all else on the circuit will go silent until RCD is reset. If I am correct, then why use an isolation transformer ?
@@cookieboi4449 Touching Live and Neutral on the mains is going to be a lot worse than on the isolation transformer and you won't need to connect scope the wrong way as even the right way will trip the RCD.
In Germany, if you create a short, you'd trip the fuse, thus cutting the power. Is there a different system in the US?
Great explanation. Can you still get shocked when using high voltage and current with an isolation transformer
Electricity is potentially dangerous with or without an isolation transformer, but when using an isolation transformer you eliminate the potential of getting shocked between yourself and a ground or earth ground connection or damaging your electronic equipment from an unwanted ground connection.
Hi! Thanks for the info!
Question, vintage radio/amps are what I have recently started working on.
So, on radios and amps that have a power transformer is the chance of a shock less than on those that do not have a power transformer?
Some videos I have watched talk about the 5 and 6 tube radios that do not have a power transformer, and thus they are more likely to give a shock if one is not using an isolation transformer. Is there any truth to that, or regardless, an isolation transformer should always be used? I have bought an isolation transformer due to your video.
Again, thanks for the info!!
I'm not knowledgeable enough to know.
In any case, I was unaware of an isolation transformer, and I learned a lot from your video. I will use it regardless from now on. Thanks!!
Transformerless, "AC/DC" radios (and any other device with the tube heaters connected in series directly to the AC mains voltage) usually have an electrically "hot" or "live" chassis, or, more accurately, you have a 50-50 chance of a "hot" or "live" chassis depending which way the old style, non-polarised plug is inserted into the wall socket, because one side of the incoming power cord is invariably connected *directly to the chassis*. To put it another way, if the chassis of a transformerless radio or amplifier doesn't seem to have measurable voltage on it, flipping the plug 180 degrees around will indeed energize it. Even if you install a polarized plug on the radio so that theoretically the chassis will only be connected to the neutral wire of the power-cord and never to the hot wire, if the wall outlet is wired incorrectly you can still end up with a hot, live chassis.
An isolation transformer, if designed and wired correctly, breaks the circuit in such a way that the "hot" chassis of the device is theoretically no longer "hot", relative to other grounded tools, appliances, test equipment, microphones and PA/ musical equipment, and even metal water pipes or electrical conduit. Not only is it safer for the technician but it will likely prevent blowing up an oscilloscope, VTVM, signal generator or other AC-powered test/ diagnostic equipment being used during the repair process.
Note that many older devices ---- radios, amplifiers etc ---- that do have a power transformer but only have a two-wire, non-polarized power cord and plug, often still use the neutral wire of the power cord as a return ground (a noise-shunting ground, really) for the chassis, with a voltage-blocking capacitor between the chassis and one wire of the power cord. If you happened to plug into the wall the wrong way around, the capacitor is supposed to prevent the chassis from becoming electrically live with 120 V (or 240VAC overseas) while still allowing a path to ground for unwanted electrical noise and radio frequently interference; and if the device hummed through the speaker you were expected to know enough to reverse the plug at the wall socket and hopefully lessen or cure the noise (or in the case of a guitar amplifier, there might be a polarity switch that accomplished the same thing without physicaly reversing the plug). The problem is that those chassis-isolating capacitors, commonly referred to as "death caps" by technicians, might be 50 or more years old, and frequently fail, and start leaking voltage onto the chassis. (Plug a vintage device with faulty wiring or a leaky death cap into a GFCI, a ground fault interrupting outlet typically found and required by code in most modern kitchens or bathrooms, and i the breaker built into the outlet will probably trip; if not, reverse the plug in the wall socket and see if it trips).
Old radios were frequently made with wood and plastic and non conductive parts and designed in such a way that it was difficult for the consumer to accidentally touch any part of the chassis that might be live, but vintage guitar amplifiers are a special case because the strings and metal parts of the guitar are at the same electrical potential as the chassis, and if the amp chassis has electricity on it and you touch another electrical or electronic device while your hands are on the guitar, or if you are playing guitar in a basement or garage with a concrete slab under your feet, you can be electrocuted (and damp slippers or socks might not insulated you sufficiently to prevent this). In such cases, use of an isolation transformer would likely prevent electrocution, and in my opinion is a must when using transformerless radios or amplifiers. Even on guitar amplifiers that already have built-in power transformers, knowledgeable techs will remove the death cap and install a 3-wire, grounded cord.
Earth-grounding a transformerless vintage radio however (or a vintage TV, for that matter?) will probably either add noise or simply result in blown fuses and breakers. I suppose you could upgrade the "death cap" to a modern "XY" safety capacitor that is specially designed to handle high AC-mains voltages, and you could also add a polarized cord so that the chassis can never be accidentally connected to the hot lead of the power cord through that capacitor (assuming the wall outlet is wired correctly ---- something that I don't like to assume!); but even if you do that I would probably suggest using an isolation transformer on it anyway.
By the way it is worth noting that transformerless, AC-DC series string vintage radios may also have a capacitor across the terminals of the on/off switch that can fail and cause the unit to be "live", or at least for the chassis to be "hot" when you least expect it because the radio is turned off! The capacitor is there to prevent premature failure of the switch from arcing at turn-on; it should probably be replaced/ upgraded; or perhaps removed entirely?
Great video. Thank you for making it. I have a question about this. Isn't it possible to achieve the same thing using a two-prong adapter? If I plug my three-prong device into the adapter and then plug the adapter into the main, did I not isolate the device from ground? Thanks to anyone who doesn't mind answering this. The adapter that I am referring to is a small, two prong (no ground) adapter. This can be seen at: upload.wikimedia.org/wikipedia/commons/thumb/5/53/Cheater_plug_edited.jpg/1200px-Cheater_plug_edited.jpg
Brad Settle I dont believe that will work because the neutral side of the outlet is still connect to your ground in your home so you would still get a ground path through the neutral. With an iso transformer there is no neutral connected to ground.
I had not watched Mr. Carlson's lab video on this in a while so I went back and watched it again, and although he shows the use of the adapter to remove the ground for a demonstration in the video he also says in the video that "I do not suggest you do so", and says you do so "at your own risk". The only real true isolation transformer does not have a ground lead at all and is the safer way to go.
I should have mentioned the do so at your own risk part in my video. It seems wrong that something that could potentially save a persons life or electronic equipment can be sold on the open market if it doesn't do what the manufacture claims. I suppose if they sell it with an attached warning it wouldn't be as bad, but I wonder why they even bother to put a ground port on an isolation transformer if using it adds the ground back to the neutral wire.
I agree with you on that. Why would manufactures make something like that. There are also some videos of people modifying isolation transformers removing the ground on them.
Yes, I'm looking at retail versions of isolation transformers and they do have a ground plug, presumably so they will meet CSA requirements for sale in my country. I must be missing a critical detail, because I don't think I understand. I assume the ground ties to the outer insulated case of the transformer, which would then be tied when you plug in to the ground circuit of the power supply or TV you are testing. Neither of the two wires coming from the secondary of the isolation transformer have a path to ground, so if my grounded body touches one of them, why would current flow even if there is a path to ground? Is it because some devices you might be testing are wired illegally, bonding neutral to ground?
Hi Sparky, The deal with non-technician isolation transformers is that they do have one of the secondary output wires bonded to the earth pin and chassis. These hospital isolation transformers are not the same as technician isolation transformers so if you have a ground pin on your isolation transformer you need to use the three prong to two prong adapter or as I did in my video "Isolation Transformer - Tripp Lite IS1000" I removed the bonding from the secondary neutral to ground. The non-technician version are to only isolate noise and high energy electrical spikes to protect equipment and not protect people from ground faults.I find this practice dangerous because such non-technician isolation transforms do not protect people from ground fault shocks and they total defeat GFIC protect at the same time.
+Todd Harrison Thank you Todd, I watched your video and the situation is much more clear. I was under the misguided impression that clipping the ground plug was all I needed to do. Since bonding between neutral and ground is internal within even a stock 'isolation transformer', as you say clipping the ground plug is not enough! Even with ground plug clipped, there is still a path from the hot side of the secondary through the hand of the tech into his feet, then back through mains ground to the transformer chassis and then to the secondary windings. To call that an isolation transformer seems like a semantic error. Somebody mentioned that if the device under test is grounded elsewhere, that third prong might also destroy the float. So, maybe the best approach is a belt and suspenders. Use a three to two prong adapter for the isolation transformer output AND be sure there is no bonding of neutral to ground internally within the transformer. When I shop for my isolation transformer locally, I'm going to check for continuity between neutral and ground output. The main damage today is I'm again wishing I had a Fluke 117, ha ha.
Good day. I have a general question about reactive power. If we supply capacitive devices through an isolation transformer, will we shift the reactive power in the inductive direction?
I can't understand your question, but I came across these Two videos on reactive power you might find of interest. Link 1 ruclips.net/video/9pWOm77KDJM/видео.html Link 2 ruclips.net/video/0f7YkVorOmY/видео.html
@@GrantsPassTVRepair Compensating the capacitive reactive power is a bit like black magic;)
That isolation transformer also sounds like something quite dangerous, because if you essentially have killed the ground circuit of the device and the case becomes hot high voltage instead of that electricity flowing to ground the way jt is supposed to in properly ground devices , that voltage now will just be waiting for you to create a parallel path on the circuit you are working. True if you nust touch something that is groo that is not creating a ground loop since your device is not grounded but instead you are working ungrounded... not safe either
5:46 The adapter you are holding in your hand will not serve as an isolation transformer, it only cuts off the earth wire. The neutral wire, which has been carried over, is till connected to earth either in your household or somewhere in the distribution system.
What will be the leakage current?
So, what you make contact with the two wires out of the isolation transformer? Is it lethal?
It could be lethal depending on your state of health, and the manner in which you're connected to the grid and ground, but it could also damage your electronic equipment not using an isolation transformer.
This is a highly informative video and I thank you for presenting this. I have a stupid question though and it involves a comparison where you pretend electricity is water instead: if this were water coming in, then the transformer would act like a filter decreasing the water pressure or amount of water coming in?
To keep the concept simple using water pressure as an example. Water pressure would be the voltage, and current or amperage would be the volume of water. Most transformers loose some current to raise their voltage output, or loose some voltage to raise their current output. To keep the concept simple picture an isolation transformer having the same input of water and the same output of water with no change in pressure or volume.
got it.
Should the test equipment use the same "isolated" AC supply as the equipment under test or can it be left plugged into the house or shop outlet?
Technically speaking It would seem you could Isolate the test equipment rather than the device being repaired to get the same end result, but this question has been raised in the past, and I vaguely remember someone giving me a good reason why it's safer to isolate the devices being repaired rather than the test equipment.
You should never split the isolated output to more than one equipment..
Hello i have to troubleshoot a few pcb with 650V capacitors on them i've always avoid them because i feared the electroshock in case i touch anything got shorted or if i touch with bare hands something , would it be safe with an isolation transformet like this? i mean no shock, no sparks in case of shorts ?
No. An isolation transformer will not protect you from shocks or shorts. It's always best to discharge capacitors before working on circuit boards.
@@GrantsPassTVRepair yes but i need to power the board to troubleshoot it so i cannot discharge the capacitor
@@MisterXS75 I understand. In that case you will just need to be careful.
@@GrantsPassTVRepair but would the isolation transformer help? Found a 1kw isolation transformer on amazon for almost 200 bucks i would save that money if it is not needed but everywhere i read this is crucial for electronic board repairing
GRANTS PASS TV REPAIR, instead of using an isolation transformer for measuring TV monitor waveforms, I have heard techs using the 2 channel oscope in the "add mode" using ch#1 to measure the tv monitor waveforms and ch#2 tied to the isolated ground/above ground point that is Not connected to chassis ground, will this work or not?
I don't understand how this can help since both grounds on the oscope are the same.
@@GrantsPassTVRepair the add mode or invert mode will put ch#2 to the isolated ground on the monitors circuit board ground which is above zero volts. You don't use the oscopes ground clips
Yes in this way you don't use the earth clips (which can either trip your RCD or possibly damage your scope) with only drawback being extra noise being picked up in the protective ground return path (since it has to come through socket wiring).
Sorry but I can't understand your question.
It's 120 240 equipment is labeled 110 220 because of a variance but it's actually a 120 volts also isolating from the ground does not protect you from getting shocked because the hot to neutral can still get you shot it will only protect your equipment. Taking the ground out of the equation when working on live circuits is a good idea however that does not prevent you from getting shocked or from causing damage. And in fact with the ground isolated you have a less likelihood of your breaker tripping and therefore saving equipment other than the one that you're working on and that's only with improper technique where you ground out
Can you safely modify a Variac by separating ground fro the neutral?
Most variac have one side of the two prong outputs permanently connected with neutral they are even worse , unplug one and put a low ohms tester between input and output you will see the short path !
If there is a ground tab on the isolation transformers cord you want to cut it off right?
I just used an adapter that didn't have a ground tab on mine and it worked fine, but when in doubt take out your meter and verify if you have true isolation. It's better to be safe than injured.
No. The ground wire on the input side is connected to the chassis and the iron core of the transformer. If somehow the isolation in the primary breaks down, it will blow the fuse or trip the RCD. If unsure, check for continuity between the transformer output and your outlet ground, there should be no connection.
In a 120volt AC circuit, neutral and earth are both possible return paths. Basically an isolation transformer eliminates earth as a possible return path?
I guess that's another way to say it.
@@GrantsPassTVRepair thanks
Don't know if you respond to this video anymore but will ask anyway. If you use an adaptor with out the ground wire connected instead of the isolation transformer will that have the same effect?
It is worse, with the ground it will trip a breaker, without you become the difference of potential, thus getting shocked
No, just removing the ground plug wont do the same as an isolation transformer, What an isolation Transformer does is isolate de neutral and hot, so you won´t have a shok if you touch any two wires coming from the output of the isolation. Remember the neutral and earth wires are join toguether before it enters your house, so isolating the neutral you no longer have that issue. The best way yo isolate (an the most dangerous) is to use an isolation transformer and don´t hook up the ground wire BUT if something goes wrong It will not trip your house or workshop breaker, so It will blow. It´s hard to understand , isolation transformer are for electrical or electronic repair guys or such,
Let's say, a transformer 230V to 230V
If you don't grounded the secondaryside, you'll have at + terminal 230V, reference to the - terminal.
But + to the ground might be higher. Isn't that a problem?
You probably should have hit the fact that there is a true separation between the physical input and output of the transformer. Another note would be the current limitation in such an incident of being shocked would be limited to the transformer maximum current which promotes less severe shocks.
Yes describing it as a physical separation would have been another good way of saying it. Regarding the current limitations of the transformer. I would not want to suggest there is any additional protection because of this. It takes less than half an amp to kill someone, so there is still the potential to get a serious shock with far less than the transformer can deliver in spite of its current limitations.
Agreed, so maybe explaining how this device can (possibly save your life) would fit with the title. And an added safety rule for all, the one handed rule. :)
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