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- Опубликовано: 10 авг 2015
- This video describes what the "phase dots" are that you often see adjacent to windings of a transformer. It discusses how these dots are used in certain circuits to establish a desired phase relationship between the signals on the various windings. A couple of tips are given regarding how to determine the phasing relationship on homebrew transformers. Finally, measurements are made with an oscilloscope on a trifilar wound transformer to see the phase relationship between the signals on each of the windings with respect to the phasing dots. Notes can be found here:
www.qsl.net/w/w2aew//youtube/... 
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Very well done. You're a natural educator.
For those that don't know both Alan and Wes Hayward W7ZOI who was the guy who did most of the work of "Solid State Design for the Radio Amateur that Alan is referencing here are Tektronix alumni. There are also many other Tek guys who have contributed much to the ham community. I am not an employee or a past employee but was fortunate to spend quite a few years as a ham in the northwest around many of these outstanding amateurs.
Tek was also an early prolific contributor to UNIX systems software (back in the 70s).They have a long history of generous contributions to several technical communities.
I wish i had discovered this channel years ago! Now every evening i am spending my time here ;-)
Egbert - yes he's great isn't he?!
Thanks Alan. It's always a pleasure learning from your videos.
I was just trying to find information on this topic. Perfect timing, and great video as always!
Good information and demonstration. Seeing the actual BB wiring and outputs on the scope was a definite plus. Thanks!
Clear and concise as always, even after 6 years!
Trying to understand bifilar toroids in joule thief circuits and your clear explanation helped me a lot. Thanks!
Still learning electronics, and You're one of my teachers (as I have no educational electronics background whatsoever). Thanks! Helps a LOT! :)
Thanks Alan, your simple explanation and example for what can be a confusing thing to actually do when building a circuit. 73 - Dino KL0S
Thank you for this easy to understand tutorial, informative.
Great video as always, Alan! Now I'm finally caught up with watching all your new videos :)
Cool! I'm looking forward to videos from your new lab!
Great job! Clear and concise. I was thinking this was right but you really cleared it up. Have to admit I was not clear, but I've had my ticket since ~1973. 73, AJ4TX
excellent video as always...keep them coming!
excellent as always, thanks you so much.
I just want to throw in that the phasing is also important with the transformers in switching power supplies.
You the man Allen. Thanks Dave
Very interesting Alan. Clarified something for me. Thanks
I have that book, bought it new a "while back". ;) Probably in 1990. I had a ton of fun piecing together bits of these circuits to build a 75m receiver on pluggable breadboards. My most advanced piece of test equipment was a Hitachi V-650F.
Thank you, Very useful, practical and clear.
Best channel out there
Very good video. Nice explanation. Thanks.
Someone commented asking about twisting wires vs. not twisting the wires. Twisted wires produce a better transmission line situation where you are using the capacitance between the wires (primary to secondary windings) along with the increased inductance due to the core to produce a transmission line of a certain characteristic impedance.
If you separate the primary winding from the secondary winding so that there is essentially zero or very low capacitance between them then you don't have this transmission line situation and the transformer is a "conventional transformer".
Transformers with either twisted wires or windings using coax are called "transmission line transformers" and have some subtle differences compared to "conventional transformers".
Probably should be the topic of another video!
Herbert Susmann Yes,, it probably would be a good video. Thanks for the technical explanation for my other viewers!
Well done. Was very easy to follow ty
So educative may God reward you
10.nov-17/ ,,Thanks for fantastic videoes Alan! ,,Both this one and all the others.
Nice schematics, explanation-cheets(goodHandwriting. goodDrawings) and good verbaly explaining.
Thank you also for often putting in metric dimensions (in adition to USsystem). Very usefull for the 'whole' Tellus/world-community techs and hobbyists. :-) ..Have a nice upcomming weekend for you and all around individs.
br, from scandinavia, norway
Rolf
Wonderful! Thanks for this.
THANK YOU. Such an easy concept if it is explained properly !!! Wish I could replace my lecturers with you XD
Great explaination. I surely gave it a big LIKE
Thanks for uploading such a great source of information. I really like your all your videos and would request for one more on how to build RF coupling transformers for driver and RF power amplifier stages. In addition, could you please demonstrate the difference between RF power transformers and normal coupling transformers. My question specifically relates to impedance matching using very simple techniques.
Excellent and brilliant explanation...
With regards with power transformers. Just by taking 2 separate secondary windings of the same values and hooking them up in series out of phase one could gain a few more volts compared to the 2 same windings in phase.
Thumbs up...
Very nice channel! Thank you!!!
awesome video!!! thanks Alan! you are Da go to electronics Guy!!!
Gave the video a like, for some reason there wasn't a mention that included the information that the windings would be in phase if they were on the same side. Thanks, that's a big help.
Great explanation. If I could take it one step further, however. It should also be noted that the CURRENT in the transformer windings for an ideal transformer goes in the OPPOSITE direction from the voltage. If current is going into the dot on the primary then it will come out of the dot at the secondary.
As Alan points out the VOLTAGE behaves oppositly: when the voltage is at it's peak on the primary (say positive) then the voltage will be at a positive peak in the secondary for dots on the same side of the transformer.
The current in the secondary produces a magnetic field that tries to buck the magnetic field produced by current in the primary. This is Lenz's law. For an ideal transformer (no leakage inductance) operating with a load on the secondary the net flux in the core is ideally zero.
Another way to think about this is think of the secondary winding as a "generator" where voltage is produced with the same polarity as the primary but current direction with respect to the dots is opposite. A generator sends current out and it can only do that if it's output is high when it is sourcing current.
These points are subtle and I have not really seen them explained well in textbooks or even ARRL publications. It is key to understanding these kind of circuits however.
Hi Alan. A follow-on video addressing current flows and corresponding magnetic fields in transformers would most appreciated!
Actually, Herbert summarized this quite nicely for you!
Howdy. On the spot.
That way my college teacher explained it.
Regards.
@@w2aew +Herbert Susmann As easy as this sounds, I'm having trouble reconciling this practical observation to Lenz's law. If the magnetic field is building on the input side, shouldn't the induced magnetic field on the output side be reacting to oppose that change? If so, why doesn't the output side have 180 deg opposite polarity? Is it because for input, current lags 90 deg behind voltage, but for output, current leads voltage by 90 deg? That way, current difference between leads on the same side would be 180 deg opposite polarity, but voltage would be in sync?
Oh, another forehead slapping moment.... Of course Lenz's law is satisfied, and of course current is opposite. I wasn't paying attention, the input coil is the load of the primary circuit, and the secondary coil is the voltage source for the secondary circuit. Indeed, current goes in opposite directions for the same reason that voltage signs flip when current into any inductor declines...
Great job...Thank you.
Thank you bro. very useful .
excellent video, thanks for taking the time to create it. WA0YMH
YOU FIXED MY RADIO! (maybe, we'll see how long it stays working....)
Yes a big Thankyou w2aew, you certainly put that across well, perfectly understandable, as with all your videos, but most hit really home.
boy I needed that
Thanks Mate
Dennis VK4JDJ
Perhaps some info on leading and lagging voltage and current as per the signal freq. and inductance and capacitance of a transformer might be interesting.
Hi, great video. In practical terms if I want to wind a SMPS EE core transformer with same polarity looking in a top view(input in left side and output in right side ) the two coils would have same rotation direction? Thank you very much.
thank you very much
very good thanks alot
Howdy.
As my college teacher explained: "The current goes in into one dot and comes out from the other dot."
Regards.
Golden Like!
I came to watch this video having the idea that if you wind a wire in the same direction it would have the same phase (represented by dot convention). But I wanted to know if you wanted your secondary side out of phase would you the wire in the opposite direction. But you just showed connecting the scope at different ends with respect to the other channels will get you 180 out of phase.....this was still a good video for in phase design concept
Either method will give you the 180 phase shift. Reverse the leads, or wind in opposite direction.
Thank you for these videos! If the secondary had a load, current would flow out the dot on the positive cycle? Since that winding would be delivering power. Does that sound right?
David Gibson Yes, exactly.
To measure the alloys in transformers, what lab equipment can you use to measure how much Iron, Nickel, metals in the transformer? Some EE techs use a Spectrometer I think. The old radios from 40's and 60's use to call the transformers "radio metal" which means that have 80% percent nickel which I'm not sure why they used so much nickel in radio transformers. The Lamination for the transformers windings was 5/8ths which for any reasons why they used 5/8ths for the lamination on the winding?
Thanks!
Thanks Alan,
rf balun needs some kind of transformers,if you find time please teach us how to use them..
Kostas - Greece.
Could you make a video about the various types of inductors?
Slightly related to this. I have a toroidal with 2 twin wires coming out of it (which i assume are the primary winding terminals) and four thicker gauge wires. How do i figure out what they are without killing myself, my measuring instrument, or both?
Thanks
Does the twisting of the wires have any significant impact on performance of transformers or inductors in general ?? - thanks for these basics videos! They are gold nuggets!!
Axel Werner See Herbert Sussman's reply for a good explanation of this.
I wish I could give this ten thumbs up!!!
The formal dot convention state that each positive current injected into a dotted terminal of a multi-winding coil, will result in a core magnetic flux with the same direction, contributing to the flux buildup. The voltage polarity is just a side effect actually...
7:36 and 7:42 - 'Break out the nail polish and let's get kinky' -Alan
When a tube amplifier output transformer is used in correctly but using a speaker impedance that is below the rated impedance will cause the reflection impedance to be doubled. If the output transformers is designed for an 8 ohm speaker load but instead some uses a 4 ohm speaker load the reflected impedance will be doubled which will cause the power tubes impedance to be mismatched with the primary side of the output transformer. This causes an audio volume drop and wattage drop, any reasons why?
How can you test the transformers laminations to know if they are high quality laminations or cheap steel laminations? anyway of testing this or how to measure a transformers eddy current? I'm not sure if a ammeter can be used to test the transformers eddy currents because the higher the eddy current this means that the transformers laminations are cheap steel?
Great tutorial as always, thank you! A auggwstion concerning the video editing: Could you try a dip-to-white or even a hard cut instead of fading between very similar images? ;-)
My Android keyboard really won this fight ... suggestion, of course.
Can you try to make a video lesson on how to use a mega to check the insulation of transformers and motors because the only way to test a transformer of the IFS a partial coils or shorting or there is this like a small internal short not all not a not the whole transformer but just partial shorts because of the insulation a mega will test the insulation voltage if there's something wrong but I don't know how to do it because I don't know what is right and what is wrong and what is considered good and what is considered bad when you have a transformer and you're running both high voltages from it to chest installation to see if there is a partial short
W2aew, Older transformers caused HUM issues, any reasons why the transformer itself caused HUM issues ? How do you measure the "Loop Area" of a transformers or a power supply? I'm not sure if linear powers supplies has less of interference issues if there is clock circuits, sync signals, switching circuit next to the linear power supply using an Iron Core transformers compared to a toroidal transformers? The interference issues i'm guessing is called the "loop Area" of the shielding needed around the powers supply so the adjacent circuts like clocks, sync circuits, switching circuits won't get into the power supply circuit.
Thanks Alan, Question will you be able to dive deeper into this topic regarding magnetics BH curve, ferrite material, core losses, wire resistance, frequency response of the material ect.. magnetics is such a miss understood subject.
***** It is a misunderstood, and often confusing subject. I'll try to do more videos on these topics.
+w2aew I would really apreciate a video thats on transformer calculations too.
very informative. One question i would like to add is how to determine the # of windings if its not writtten of specified in the schematic? some do put values while others do not
There are several variables. The frequency of operation, the impedances of the circuits, and the ratio needed, along with the core material used, all feed into the number of turns required. For 1:1 ratio transformers, it is common to have sufficient turns to get an inductance value at least 4x the system impedance at the lowest frequency of operation.
Amazing, Just the output frequency of ch1 ch2 ch3 are different or only phase or shape different?
Frequency is the same on all three, just the phase is different.
Clicked straight on the like button as the answer was on the screen at the very first second (refreshing memory), no need to hear 30 minutes of blah blah like on some other channels;) Shall watch the rest no worries...
What causes a transformer to get hot after it being turned on? Units that have MOV varistor will be PTC or NTC that are directly sitting on the transformers housing chassis and will shut the unit off when the transformers housing chassis gets to hot. Some MOV varistors that are PTC or NTC are MOV varistor temperature compensation types and other MOV varistors are clamping voltage types. The MOV varistors that are temperature types lay sitting on the transformers housing chassis and will turn off the unit when the transformer gets to hot. But what makes the transformer get to hot because the lamination is weak or the coils are shorted internally?
The answer is cheesy, but it's insufficient cooling, if the transformer is not defective of course. Main losses are from I^2R losses in the windings. Eddy currents also contribute but the magnitude is dependant on the quality of construction. Maybe eddy currents in the housing? If the windings are shorted, the transformer ratio and winding impedance will be off. Transformers can have significant inrush currents but they shouldn't persist long enough to cause heating issues.
hi allan I follow you from France and thanks for your very instructive tuto. Could you please one day make a tuto about the mixing of the voltage.between ac and dc voltage in the same circuits. how it works. The dc voltage supplying the devices and ac voltage coming from the signals are "mixed or added". There are extract after one of the other one and used.Thanks
Eric Le Roux Sure, I'll add that to my list. This is very common in RF applications.
May I please ask you about 8:22? As I understand it are all those windings in phase but you have decided to put the ground on opposite sides, and that do put them in 180 deg out of face. Does that mean if I have a transformer where the "dot" is not all in the same side, do I just have to move ground to the opposite side and all of them is now in phase?
Yes, the dots indicate the phase, not the position of the winding on the core.
So you're saying if you have an outlet that is wired correctly and have a piece of equipment plugged into the AC outlet and another outlet that is wired reversed polarity and have a piece of equipment plugged into that AC outlet. If you put your hands on both unit metal chassis this can cause a safety problem issues because one chassis is ground while the other is live chassis? I thought they would be both earth grounded regardless of the AC outlet polarity.
If an output transformers secondary winding is rated at 4 ohms load and you put 3.2 ohms which is a mismatch, what will happen to the impedance on the transformers primary and impedance of the output tubes. This mismatch causes a type of distortion from the mismatch. I'm not sure what this is called when you do something like this but it's some type of electronic term.
If you put a 3.2ohm load on an audio transformer rated with a 4 ohm secondary, the main result is that the input impedance looking into the primary will be 80% of the rated primary impedance. Thus, it will present a slightly heavier load. There may be additional losses in the transformer as well.
Hey-o,
How would we do a 90deg phase shift?
Is it possible with this?
Great videos as always!
73
Not possible with simple transformer phasing.
w2aew thanks much, your videos are great as always!
Does this apply to the secondary winding of a single phase step down transformer. Meaning 1/2 wound one direction to the center tap and
the remaining 1/2 wound in the opposite direction. 180 degrees out of phase?
That's one way to look at it. From the center tap's perspective - each half of the winding is done in an opposite direction.
@@w2aew Upon further education (3 years into it) I would never expect
to find the QUESTION I asked before. Both halves would not be wound in opposite directions. However we can have a SECONDARY to be either ADDITIVE or SUBTRACTIVE depending on the size of the can.
Thank you. Thusv conversation is all about residential power distribution. Self taught.
Could you give us a couple (pun painfully intended) examples of why in phase would be desirable, and also out of phase would be desirable in a circuit? For example: an early single ended guitar amp? Thanks Alan! Great video BTW! ;)
The most common application where the phase through the transformer matters is when the transformer is part of a feedback loop, where improper phase will cause the circuit to not work.
0:35 Doesn't the Xformer shift the phase 45 degrees since the output is (I believe) the derivative of the input?
Power Max If the transformer is properly designed for the application (and the winding inductance doesn't enter into the picture), then ideally no phase shift occurs. In reality, there is always some shift, but not 45 degrees. If it was a derivative, the phase shift would be 90...
***** right, I need to learn my degrees, that's what happens when you learn math in radians :-/ but anyway, I thought because the secondary's output is proportional to the change in magnetic flux in the core, seemingly meaning that the output would be phase shifted.
Power Max OK so I think I figured it out, the primary is an inductor, so the phase of the current lags behind the voltage across it, that current is directly proportional to the magnetic flux, and the secondary current is proportional to that magnetic flux, responding to how it changes over time, so then the current/voltage is shifted back to what is was originally? right?
Electronic Engineers say that Toroidal Transformers have less leakage current, what do you they mean by a transformers having less leakage current? Do they mean from primary to secondary leakage current current? more isolation from primary to secondary?
When the hot and neutral wires are reversed polarity on the AC outlet why does it cause damage to computerized circuits or digital circuits? the primary of the transformers doesn't care because its an AC signals but I'm guessing the power transformers secondary winding current is flowing in reverse which causes digital circuits and computerized circuits to get damaged or not like it any reasons why? Also older circuits in the 70's and 80's used negative power supplies and positive power supplies in a circuit, but now modern circuits try not to use negative voltages and negative power supplies, any reasons why?
If hot and neutral are reversed, then the safety ground connection is compromised. If another peripheral (printer, monitor, etc.) is connected which is powered by a different outlet, then it's possible to have a problem with the chassis grounds.
One reason why positive and negative supplies aren't as common today is cost. Circuits have developed to use single supplies to help safe the cost of an extra power supply rail.
When visually looking at a transformer or measuring them, how do you know if the transformer is a galvanic isolation? I'm not sure what make a transformer have galvanic isolation. The iron core and wiring wrapped around the bobbin or slug is the transformer part but what is the galvanic isolation part of the transformer to make it galvanic?
Galvanic isolation means that there is no DC path between the primary and secondary - that's all. You can easily verify this with an ohmmeter.
@@w2aew The Iron Core or what is causing the Galvanic Isolation and preventing there is no DC path? because all transformers even Non-isolated transistors have Galvanic isolation. I'm not sure why its advertised that ONLY isolating transformers only have Galvanic isolation and other non-isolating transformers aren't advertised as having galvanic isolation.
@@waynegram8907 are you talking about safety transformers? In all transformers the windings are isolated from each other. In safety transformers, used on construction sites for example, there is additional isolation seperating the windings so primary and secondary can never short. The secondary winding also remains floating from ground, so a fase to ground fault in equipment does not cause high fault currents. I do not know why they call this galvanic isolation. I understand your confusion.
@@w2aew How can you tell if an output transformer has an internal air gap because some transformers are called air gap transformers. What does the air gap do because it suppose to allow DC current and DC voltage to go through the transformer coil?
@@w2aew Galvanice Isolation means that the mutual inductors between primary coil and secondary coil is ZERO. How can you measure the transformers "mutual inductance", using an LCR meter? because most transformers tell you the turn ratio TR the primary number and secondary turn number but they don't tell you the mutual inductance between the primary coil and secondary coil , any reasons why?
I never came across those solderable dip things, do you have a good search term for them?
Dennis Lubert These are called DIP headers, or DIP Component Carriers. Examples:
www.allelectronics.com/make-a-store/item/dh-14w/14-pin-dip-header-wide-0.6-spacing/1.html
www.goldmine-elec-products.com/prodinfo.asp?number=G18626
www.newark.com/aries/16-600-10/dip-header-16pos-through-hole/dp/03M3026
Ah thank you! BTW, love your videos
Thumbs up done is the dot symbolized the the starting point of a coil sir is my understanding is right
That's one way to look at it.
@@w2aew tnx for the info sir
w2aew, for center tap transformers that use the center tap as the ground, when disconnecting the center tap from ground the other voltages which drift higher or lower. When a 12VAC center tap transformer center cap is disconnected from ground, each side of the transformer will drift higher or lower but will equal to 24VAC. If one side of the transformer lug measured 12VAC referenced to the center tap to ground and the other side measure 12VAC referenced to the center tap to ground that is 24VAC from outside lugs. But when disconnecting the center tap from ground the output lugs will drift higher or lower but will still equal to 24VAC. Any reasons why the output legs will drift higher and lower in voltage and not be "matched" at 12VAC?
The ends will always be matched at 12VAC with respect to the center tap. But, if the center tap isn't connected to ground, the voltage from either end TO GROUND can be anything because it is isolated from ground.
When the center tap isn't connected to ground, why aren't the ends matched to the same voltage? The transformer windings from the center tap to each end should have the same winding turns ratio so they should have the same voltage even if the center tap is not connected to ground.
@@waynegram8907 They Do have the same voltage when measured with respect to the center tap, but they won't necessarily be matched when measured with respect to ground. This is because the center tap is not tied to ground.
That is what I'm confused about is why won't they be matched with the center tap is not tied to ground. They should be matched because the winding turns/DC resistance from center tap to end lug are the same. The transformer windings should be symmetrical from each end lug to the center tap
@@waynegram8907 If you measure from either end to the center tap, they WILL be matched.
Does anybody know the name of that piece he had the coil soldered to?
It is called a DIP Adapter Header, such as:
www.jameco.com/z/14-600-10-Aries-Electronics-Connector-DIP-Adapter-Header-14-Position-2-54mm-Solder-Straight-Through-Hole_291312.html
sir may I ask you a somewhat related question? I am wondering if we can connect the primary windings of an audio isolation transformer to the output of a class B direct coupled amplifier and the secondary windings to the speaker? Will the output of the amplifier be affected in a harmful way due to the impedance of the primary transformer? Using a one to one turns ratio.
If it is a one-to-one turns ratio, then the impedance at the primary will be equal to the impedance connected to the secondary. In other words, the amplifier output will "see" the speaker impedance.
@@w2aew Thank you! I appreciate it.
@@w2aew I am just concerned if the primary windings will look like a short to the amplifier output with or without any speakers connected to the secondary.
@@uiticus It will look like a short at DC (biasing), but will reflect the secondary's load impedance at audio frequencies.
@@w2aew Thank you sir. Much appreciated.
What causes transformer hysteresis? because the transformer hysteresis will cause a voltage drop from primary to secondary, not sure why
Remenant magnetism in the transformer core. The current magnetises the core and the magnetic field generated has a polarity, direction, whatever floats your boat, that is a function of the direction of the current. If you turn the current back to 0, a small magnetic field remains in the direction of the current. If current starts flowing in the reverse direction, it has to 'undo' the remaining magnetic field first before a magnetic field in the other direction can build up. This is what causes the hysteresis loop.
So if secondary winding is wind in opposite direction, dot on secondary will be on down side?
yes
One more question, bifilar winding on E core vs toroidal 1:1 winding for isolation transformer purpose?
Often times a negative feedback comes off a tube output transformer secondary back to the cathode of an input. Get the transformer phase wrong and things don't work as expected!
3 phase transformers will have 208VAC outputs, its 120VAC +180degrees = 208VAC? The reasons why they used 208VAC instead of 240VAC was that 208VAC produced less heat dissipation and didn't wear out the AC motors in house equipment?
In a three phase transformer the phases are 120 degrees from each other. The phase to phase voltage is 120 V times √3. The advantage is that the delivered power from a 3 phase configuration is really smooth. Power from a single phase is actually a 100 Hz pulse while the motor tries to deliver continuous mechanical power. So it starts vibrating.
Edit: probably a 120 Hz pulse where you live.
Wow।। VU3ICT
A general rule of thumb is the primary is "always 10X" what the secondary impedance rating is? The output transformer is rated at 4 ohms means the primary is 4ohms X 10 = 40K ohm primary impedance? if you put a 3.2 ohm load that is 3.2ohms X 10 = 32K ohm primary impedance. For amplifiers speaker cabinets if they have 2 speakers at 8 ohms it will be connected for 4 ohms, if you have a speaker cabinet with 3 speakers at 8 ohms it will measure 3.2 ohms. The Mismatching of the 3 speakers at 8 ohms measuring 3.2 ohm impedance while using an output transformer rated at 4 ohms does what you think? It put more of an "impedance load" on the final output power amplifier?
I don't believe that it is "always 10X". It all depends on the design of the transformer. Audio transformers are rated for specific primary and secondary impedances.
Hello could you test this software? Search androidcircuitsolver on google
Thanks