Please help me identify this transformer - Page 1
Forum section: electronics / beginners

author: kgavionics
author_rank: Regular Contributor
timestamp: September 06, 2021, 01:56:02 am
content: Hello guysI have found this big transformer in my storage and I can't remember where I did take it from. There is a marking on the transformer (see picture) U96AE-50V2JJ2 and below it J2802210054X. I looked over the internet and couldn't find something with the above numbers.I took some resistance measurement (see below) and I couldn't understand why all the values are under 4 ohms.Can someone help me identify this transformer please?Thanks in advance.J1 (yellow-black-yellow)Resistance between yellow - yellow -3.16ohmsResistance between either yellow and black is 2.4 ohmsJ2 (red-green-red)Resistance between red - red -2.09ohmsResistance between either red and green is 1.76 ohmsj3 (blue-blue-brown-brown)Resistance between blue-blue 1.91ohmsResistance between brown-brown is 2.76 ohmsj4 (black-red)Resistance between red and black is 2.61 ohms

author: bob91343
author_rank: Super Contributor
timestamp: September 06, 2021, 03:08:29 am
content: Looks like a power transformer. The blue - brown leads I would guess are the two parts of the primary, to be wired in series for 240V and parallel for 120V.If you have a variac you could power it at low voltage while monitoring the current and see if current stays low up to full voltage. Then measure the other voltages to see the outputs.I suspect your resistance readings are in error; resistances this low require four-wire ohmmeters.Weigh the transformer and compare it to catalog listings to estimate the total power. When you get good resistance readings you can decide how much power each winding can supply.

author: floobydust
author_rank: Super Contributor
timestamp: September 06, 2021, 03:29:59 am
content: It's got an outer electrostatic shield, so likely from some audio gear or test equipment.The blue and brown wires are different, no UL/CSA approvals or text written on them for some reason.I take a wild guess which is the primary winding, inject a few VAC sine-wave from a signal generator at say 1kHz and measure the voltages, to figure out the turns ratios for each winding. Most important is to ID the primary, and not get zapped if you are injecting backwards i.e. 1VAC to a 6VAC winding and getting 20VAC out of the primary.Your ohmmeter readings do not make sense, as the windings with a center tap should be half the value of the end-end resistance. Some multimeters have issues measuring resistance of something with high inductance, such as a transformer. You can try short one winding while measuring another's windings resistance- it should make no difference but will if the multimeter is oscillating.

author: kgavionics
author_rank: Regular Contributor
timestamp: September 06, 2021, 03:50:27 am
content: Thank you guys for your inputs, it's very much appreciated!I used my Brymen 869S to measure the resistance! but,I have an old fluke 8060A so, I'll try it and see if it can make a difference!Unfortunately, I don't have a variac, so I'll try a signal generator like floobydust suggested, and I'll report back

author: bob91343
author_rank: Super Contributor
timestamp: September 06, 2021, 04:01:21 am
content: The two halves of a center tapped winding are seldom equal resistance, due to the amount of wire needed. One half is wound first so the second half uses more wire. This is not true for bifilar windings but it's seldom done this way without a more compelling reason.

author: floobydust
author_rank: Super Contributor
timestamp: September 06, 2021, 05:19:50 am
content: OP is getting 3.16ohms end-end and 2.4 at the center-tap, other winding 2.09ohms end-end and 1.76 at the center-tap, all of which is way off even if the windings are not bifilar.I sure hope it's not the ohms current-source oscillating, that would make me cry. It is an issue with the Keithley DMM6500https://www.eevblog.com/forum/testgear/keithley-dmm6500-strange-beahavor-measuring-transformer-resistance/

author: james_s
author_rank: Super Contributor
timestamp: September 06, 2021, 05:22:55 am
content: A signal generator will work, but use 60Hz, not 1kHz.Another thing you can do is wire it up in series with an incandescent light bulb and take a guess on what you think is the primary. If you get it wrong the bulb will light up brightly instead of the transformer burning up.

author: bob91343
author_rank: Super Contributor
timestamp: September 06, 2021, 05:50:38 am
content: floobydust, if we assume .7 Ohm offset on the two readings they become 2.46 and 1.7 ohms, much closer.Another (but unlikely) possibility is that it's an audio transformer. So two identical windings would be for the plates or collectors of a push pull amplifier.

author: floobydust
author_rank: Super Contributor
timestamp: September 06, 2021, 10:15:26 pm
content: I can't recommend connecting any unknown transformer windings to mains, even with a current limiter/variac- I prefer using a signal generator doing low level measurements first to ID the HV windings.The voltage could be high, a 20:1 turns ratio run backwards is not fun i.e. 6V secondary connected to 120V mains but core saturates or light bulb is on- still HV at the primary. Or it's a surprise plate transformer.I found no difference between 60Hz and ~1kHz excitation, it's just faster for the DMM to settle and once I had hum or noise when measuring AC mV hetrodyning with mains, doing this away from the quiet bench. The readings were jumpy.

author: gbaddeley
author_rank: Regular Contributor
timestamp: September 06, 2021, 10:33:02 pm
content: Another source is a step down transformer, to less than 10 V. Connect it across the blue wires, as this is suspected to be a primary winding. Measure voltage between all wires, and write down as a matrix. Number the wires rather than go by colour, as there are duplicate colours. Put a resistor across the meter leads, eg. 1K Ohm 1 Watt, so that you don’t get false readings due to capacitive leakage between the windings.If you get any readings much higher than the input voltage, it may be a winding for a VFD or HT for a vacuum tube.If you are confident that you have a mains primary winding, power it up through a variac. If the tranny does not hum loudly or get hot after a few minutes it is probably ok. Measure the other windings again and confirm the ratios match the original meaurements.Put dummy load resistors across each winding in turn, to draw a couple of watts. Work out the % sag. If it’s less than 5% it is probably ok to draw that much in a real circuit. Be conservative. YMMV.

author: bdunham7
author_rank: Super Contributor
timestamp: September 06, 2021, 10:48:21 pm
content: You need to figure out how to zero your ohmmeter as I think there's a huge residual reading that is shifting the values. That or there is some other problem, so try your other meter as well. Also, you should do this as a matrix and clearly indicate the combinations that are open as well. For example, is there continuity between black and green?How big is this thing? Can you show a ruler or something for comparison?

author: kgavionics
author_rank: Regular Contributor
timestamp: September 07, 2021, 11:06:57 pm
content: Hello guys, and sorry for the late reply, I was so busy, and I didn't find the time to check your suggestions out, but I'll try it to do it tonight if I have some spare time!Regarding the size of the transformer, it's a quite heavy! It weighs 3.5 kg, and it measures 12cmx11cmx9cm.

author: MultiMike
author_rank: Contributor
timestamp: September 07, 2021, 11:13:18 pm
content: Since the wires are CSA rated and there is an 'H' on it my gut is telling me that it's a Hammond transformer, made in Guelph, Ontario Canada.I'll try to dig around for more info, if I can find any.Mike

author: kgavionics
author_rank: Regular Contributor
timestamp: September 09, 2021, 12:34:39 am
content: Hello guysBy wiring the primary (blue-brown) in parallel and applying a sin wave of 5Vrms to it, I got the following voltages:yellow-black-yellow=0.42Vrms (half of it if I measure from the centre tap) ratio=12red-green-red=0.91Vrms, gives me a ratio of 5.5all is clear for now, except the purpose of the auxiliary primary winding (Red-black), by leaving it open, I got the above results, but if I short it out, the yellow-black-yellow and the red-green-red ratios become, respectively, 40 and 20. Can someone shed light on the purpose of this winding, it would be very much appreciated!

author: gcewing
author_rank: Regular Contributor
timestamp: September 09, 2021, 01:15:15 am
content: Shorting out the red-black winding doesn't seem like a useful thing to do.What voltage do you get from it?

author: floobydust
author_rank: Super Contributor
timestamp: September 09, 2021, 01:16:31 am
content: Please let us know if your Fluke and Brymen both read the same for DC resistance.Also, when any one of the other windings is shorted. Any ohmmeter reading between the pairs like red-blk and blue-blue to brn-brn etc?Sometimes wires might be for an inner electrostatic shield and not actually connect to anything but a foil shield, but that would be not a pair, just a lone wire.What AC voltage did you measure on red-blk? It's confusing what you're saying, the voltages measured are end-end i.e. yel-yel and red-red?

author: bdunham7
author_rank: Super Contributor
timestamp: September 09, 2021, 01:49:02 am
content: The primary may be some arrangement that allows switching windings around to use 100/120/220/240 volts (or something) and that can be tricky to figure out. Do you have an LCR meter, and/or a scope to check phase with?

author: kgavionics
author_rank: Regular Contributor
timestamp: September 09, 2021, 02:15:04 am
content: HelloRegarding the resistance, I made a table comparing the results with the Fluke and Brymen ( see attached screenshot). It doesn't matter if I measure directly or using a 1 Ohm resistor as some of you have suggested!@bdunham7 : I do have an oscilloscope, but no LCR meter!@gcewing : when I apply 5Vrms to the primary, I get 1.26 Vrms on it (Black-Red)

author: bdunham7
author_rank: Super Contributor
timestamp: September 09, 2021, 02:24:31 am
content: What do you get on each meter when you just short the test leads together? I'm guessing about 0.7 for the Fluke and 0.4 for the Brymen?

author: kgavionics
author_rank: Regular Contributor
timestamp: September 09, 2021, 02:26:29 am
content: Brymen=0.24 OhmsFluke =0.57 Ohms

author: bdunham7
author_rank: Super Contributor
timestamp: September 09, 2021, 02:32:55 am
content: Quote from: kgavionics on September 09, 2021, 12:34:39 amOK, so I'm not clear on that part. Can you diagram out how you did this? If I understand, there is no continuity between any of the blue wires and any of the brown? And they are different resistances? You need to apply your 5V RMS to individual windings only if you want to figure anything out. Also, label your pairs of the same color with A/B or 1/2.Edit: What I'm getting at is that you need to know thepolarityof the windings in order to properly figure out what's what.

author: floobydust
author_rank: Super Contributor
timestamp: September 09, 2021, 08:13:13 pm
content: It's strange because a dual-primary needs phasing or polarity. The blue-blue and brown-brown don't have any markings and you need to know this in order to assemble the connector at the factory. It could have selectable line voltage but still need to know hi/lo. The red and black must be related to another winding.The "H" with wings icon I could not find who makes this.