Transformer ID

[KB9YSJ]

Hello, I am trying to identify this old Transformer. Has anyone seen this B4. Brand name and voltage layout?? Thanks

[K3YA]

Looks like a pole pig that was pulled out of it's oil.  It was common to run them that way once upon a time.  You will have to figure out the turns ratio yourself by energizing the low voltage side, that you will use as the primary, with 6.3 VAC and measure the voltage on the high side.  There will be taps, and possibly a jumper to allow small changes in the turns ratio to adjust the line voltage in it's original usage.   

[Opcom]

Because it is being used backwards, it might be necessary to use a higher voltage to make enough flux to energize it for testing. The pole pigs I have seem to take about 2A to magnetize with no load. Or apply 120V to the secondary and measure the primary.

[KB9YSJ]

Thanks for the reply. I will try that.

[Opcom]

Please do! That is, try both ways and let us know, it will be a good datapoint to compare with others.

Here's a pic of one of mine before they got cleaned up. I notice an interesting  difference, I have these off 3-sided cores, but yours looks much newer, probably a much better technology unit.

I think these things must have very good insulation. There has never been an issue even when they were hooked up with one side of the secondary grounded, each transformer a half wave unit, and the opposite transformer supplying the second "half" of the virtual 4800-0-4800 secondary and each side had two MV rectifiers in parallel. They sit on a wood deck in the bottom of the TX but they are definitely grounded by the metal mounting bars.

I don't think mine have ever been in oil, too clean and only dust, no oily or greasy stuff has ever soaked out, even after 55 years. (Now they are set up for separate 2400-0-2400 windings each with a FWCT rectifier, I am afraid to stress them to the full voltage due to age)

I guess the days of picking these up from the power company for a few dollars are long gone.

[K3YA]

Cool photo.  I have 2 pole pigs in my collection and have picture on file of one of them.


I bought it at the AM table at the Gathersburg Hamfest many years ago.  Some of the board members may know it's history.

Last time I used it was to energize a Tesla coil to produce 5 foot sparks.  But, it was too powerful and overheated the spark gap ofter only a few seconds of glorious fireworks.  Prior to that it powered a GG 4-1000, which it did quit well.

[KB9YSJ]

I did some testing on the Transformer 20VAC on the Pri gave me
 590vac on taps 2-3
572vac on 3-4
438vac on 4-5
615vac on 1-2
575vac on 1-5
 All taken from the 2 outside taps secondary.

[Opcom]

Something is weird. What about when 20V is put to primary terminals 1-3? Do all primary terminals have continuity to each other?
The voltages in the list do not seem to add up even with phase reversals.

what I mean, is all the voltages are close, so how can there be almost the same voltage induced by powering 2x the winding as 1x.


Anyone agree or disagree?

Otherwise can you put 100V on the secondary and, with a load, such as a 100W lamp attached across the meter probes, check the terminals like:

1-2
1-3
1-4
1-5

2-3
2-4
2-5

3-4
3-5

It might make a difference with  small load.

[KB9YSJ]

I may be testing it differant then you think. Call me so we can get the info correct               Jeff@KB9YSJ.COM

[k4kyv]

Pole pigs have fallen out of use by hams these days because the ones hams used in the late 50s/early 60s were usually rated at 3 KVA or less.  Those, originally installed in the 1940s and before, were pulled off the poles as post-WWII electricity usage soared, and most homes demanded more than 3 KVA, so they were replaced by 10, 15 and 25 KVA ones. Usually, the utility company would sell them to hams for what they were bringing as scrap metal, about $5 per transformer.  Now, very few crapped out pole pigs and ones upgraded with larger sizes are in the <3KVA range.  10, 15 and 25 KVA units are far too big and heavy for most ham use.  Also, power companies are undoubtedly more paranoid about lawsuits than they were back then, so they probably wouldn't release even a tiny 1.5 KVA one.  Would they be legally liable if the ham managed to get electrocuted off his power supply, using a pole pig they had given or sold to him? Also, hams in those days had a better reputation for being technically competent to work with electricity, than do the hams of to-day.

The one shown in  the first photo looks almost identical to the pair of Wagner 3 KVA, 7200v pole pigs I still have.  Mine even came with a factory-installed midtap.  Many transformers did not, and you either had to find the correct turn, dig it out of the coil and attach a connection to it without damaging the winding, or else use the transformer with a full wave bridge.  Smaller 2400v 1.5 KVA units worked well with the bridge circuit.  I always had to reduce the voltage to my 7200v ones, because the output voltage in the full-wave CT circuit was right at the ragged edge of the maximum PIV ratings of 866As and 872As. A pile of solid state diodes was prohibitively expensive back then, and despite taking all the recommended precautions, strings of diodes with equalising resistors and by-pass capacitors across each diode eventually blew up in every power supply I built, like lighting off a string of firecrackers. Now, in my Gates BC transmitter, I use commercially manufactured plug-in SS replacement modules for 8008s and 866As, and have never had a problem with them.

[Opcom]

I may be testing it differant then you think. Call me so we can get the info correct               Jeff@KB9YSJ.COM

I can't dial that on any phone around here!


Don: Then the days of hammy pole pigs are gone.. pity. 7200 is a lot of volts. Lucky you have the CT on those of yours.

There's a nice 120/240/4160V 10KVA control transformer a guy has for sale in Forth Worth but he wants more than it is worth.
It's not a "pole pig" but is equivalent to one as a ham item. 4160VAC@2.4A is a bit low (3700DC) for most single tubes if a choke input filter is used but it might make for powering a real nice final and set of modulators. Something wild like 2x4's modding 2x4's