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Old 15th November 2007, 11:46 AM   #1
engels is offline engels  Israel
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Question Decoding another recycled power trans

Another question about recycling transformers. I've got one very heavy one which is labeled "Advance", made in England. It's approximately twice heavier than another PT for 2XEL34 I've got. It has two completely separate coils, one about twice bigger than the other.

Click the image to open in full size.

I've pulled it from a big steel wadrobe in a destroyed computer centre, it was a part of a power supply (it is called UPS?) - I couldn't see what voltages this unit was operating, it was not labelled.

Terminals 1-2-3 are probably a CT primary and terminals 5,6,7,10 are probably the secondary which puts out about half of the primary with several low voltage taps.

Click the image to open in full size.

Everything is good except for one thing: The secondary takes twice the space of the primary and puts ~ half the voltage of the primary. The coils are well insulated so I couldn't see the wires but the wires at the terminals look all the same (pretty thick btw).

I'm not good at analyzing transformers, so what's the story here? Is there a 10A super-thick winding for 24VCT underneath?

I was thinking about possible uses for this thing:

One option is a 4 X 21GY5 PP amp [21GY5 is a very cheap compactron beam pentode, 18W plate 3.5W screen dissipation, 21V @ 0.45A heater and around 130V @ 50mA plate and screen typical]. The OT should be something 100W EL34-esque with ~ 2000 CT primary, I've got something like this. The tapped secondary may give me 22VAC for the power tubes' heaters, 11VAC for some 12V preamp tubes and 124V for B+.

Or maybe I should feed 230V to half of the primary and get 294V secondary for something more conventional? I will need a filaments' transformer then.

Or use it backwards and have 330V from 1-3?

Ehhhh.... again I'm typing too much.

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Old 15th November 2007, 12:33 PM   #2
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It might not be a mains transformer if its from a UPS. A UPS is an inverter that runs from lead acid batteries. Some "online" UPS run constantly to isolate the output from the mains input.
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Old 15th November 2007, 12:35 PM   #3
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I can't tell from the picture, but it looks like a ferroresonant transformer. The secondary has a tuning capacitor (multi-uF oil cap) to tune it to 50 or 60 Hz, and they provide regulation over a range of input voltages.

They're noisy and draw a lot of exciting current (low power factor on input). But copper is over $6 a kilo...
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Old 15th November 2007, 01:40 PM   #4
engels is offline engels  Israel
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Default ferro-what???

here's a closeup of the label.
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File Type: jpg advance-label.jpg (73.4 KB, 84 views)
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Old 15th November 2007, 02:44 PM   #5
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ferroresonant transformer also known as a Sola. They are used to regulate AC line voltage. Kind of obsolete in todays world of switching supplies and voltage regulators. A big deal in the tube era...
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Old 15th November 2007, 02:59 PM   #6
engels is offline engels  Israel
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Default it's new

I think I forgot to say one important thing - this transformer is by no means from the tube ages. The whole UPS was about 10 - 15 years old, not more than that. I think there were also power transformers in that construction - huge 400V boxes that I was unable to lift or carry. This transformer was somewhere on a side and I have no idea of it's function.

It also looks fresh, no rust. It was soaked in some sort of wax which gives it sort of a funny look with tiny bubbles all over the frame.

It looks very solid and I'm sure it can handle a lot of current. The thing that bothers me the most is the sizes of the windings - seems like I'm missing some point which may become a problem.
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