Basic Transformer Question

I have a transformer with a 120V primary and a center tapped secondary, each side producing 51V. I can see 4 wires comming out of the secondary A, B, C, D where B & C are tied together forming the center tap. I want to get more current at 51V than each individual side can provide. Is there anything wrong with breaking the connection between B & C and connecting A&C together and B&D together to make the transformer into esentially a 120V primary, 51V secondary? I know I could just do it and see what happens, but this is a heavy duty transformer and I don't want to mess it up. Any advice would be greatly appreciated. Thanks

Reply to
jalbers
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Conceptually, there is nothing wrong with paralleling two similar windings to get a single output with a higher current capability. But, if one winding has any difference in turns count than the other, the slight difference in voltage will cause current to circulate through the two windings, heating them up.

I would connect one pair of ends together and measure the voltage between the remaining pair of ends, to make sure that this voltage is essentially zero, before connecting those ends together.

Reply to
John Popelish

Yes, you can do that.

As John says though., you need to be sure that both windings are of exactly equal voltage ( i.e. the same number of turns ).

Graham

Reply to
Pooh Bear

I tried it and it seems to be working ok. There is a small voltage difference of around .020V or 20mv. It doesn't seem to be causing any overheating or other problems.

Reply to
jalbers

That's fine. In practice the 2 windings won't be *exactly* the same voltage down to the millivolt level.

Graham

Reply to
Pooh Bear

I hooked up a 7 amp load to the transformer last night and it is not even begining to show any signs of strain. I was using a DVOM with the

10 amp AC setting. The DVOM was rated to function to 10A but the test leads that came with it were certainly not. Before I reallized what was happing, one of the test leads burt up. I don't think it hurt the DVOM though.
Reply to
jalbers

the safe way:

disconnect B and C , measure the resistance between A and C (it should be infinite), if it isn't stop. connect A and C power it up and measure the voltage between B and D, it should be 0, if it is it's safe to connect them.

Bye. Jasen

Reply to
Jasen Betts

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