Can I use a 200-500V in and 460 out transformer to make 208 from 240?
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Thread: Can I use a 200-500V in and 460 out transformer to make 208 from 240?

1. Diamond
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Can I use a 200-500V in and 460 out transformer to make 208 from 240?

I have a 30KVA transformer that I kept off a machine I scrapped. I thought the machine was 208 volts, but turns out (after I mounted the transformer to a new machine haha) that the damn transformer puts out 460/266 volts.

Sooo, seeing as I don't have another transformer and I went through a lot of work making nice mounting brackets for it what's the chance I could plug my 255ish volts into the 460 side of this transformer and set the taps for like 418 volts and and end up with 200-210 volts coming off the input side to feed my 208V machine?

Thanks!

2. Nowhere near enough information. Does the transformer have a diagram on the nameplate? Single or three phase?

As a general answer, transformers work both directions.

Bill

3. It is eighter 8% down or 125% up
So a 255V input can give you eighter 255-8% =235 volts or 255+125%=319 volts
Peter

4. Diamond
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It's 3 phase. The primary side has taps from 200v to 500v for incoming voltage. The secondary side is 460.

My question is basically if a transformer designed for 460v will still work the same on 240.

My math says 460 is to 380 same as 255 is to 210. So 380 tap might work to get 210 from 255.

5. Stainless
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You won't be able to pull 30 kva through it, but if the draw isn't a ton it should work. The transformer doesn't know the difference. The windings would only be good for something like 10kva before you run out of current capacity.

6. Diamond
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Originally Posted by Comatose
You won't be able to pull 30 kva through it, but if the draw isn't a ton it should work. The transformer doesn't know the difference. The windings would only be good for something like 10kva before you run out of current capacity.
10 KVA is not good. It's a 20HP Mori SL2H and it's rated for 30KVA, so probably realistically needs 20KVA.

I'm going to put the fuses in and throw the switch in a minute here and see what voltage I get hooked up this way. If it works I will use it to fix a few things on this machine and buy a different transformer as soon as I can afford it.

7. Diamond
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I tapped it for 380 and I get 196 volts off the primary which is good enough for me.

I added a pic of the info plate. Maybe this might help figure out how much juice I can pull through it hooked up backwards.

8. Stainless
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Originally Posted by Garwood
I tapped it for 380 and I get 196 volts off the primary which is good enough for me.

I added a pic of the info plate. Maybe this might help figure out how much juice I can pull through it hooked up backwards.
the secondary you are feeding with 240 appears to be rated for 33 or 35 amps. so, on the order of 13Kva.

since the voltage is lower and you're not using the full primary winding, you may be able to push it a bit more. plus it takes a few hours for a transformer that size to heat up. so, monitor the temperature and the amps and it may work for you.

9. Diamond
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Originally Posted by johansen
the secondary you are feeding with 240 appears to be rated for 33 or 35 amps. so, on the order of 13Kva.

since the voltage is lower and you're not using the full primary winding, you may be able to push it a bit more. plus it takes a few hours for a transformer that size to heat up. so, monitor the temperature and the amps and it may work for you.

Thanks, I really appreciate the advice!