Using 230v transformers on 115v primary

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Posted on October 21, 2016 at 00:10:23

andy evans
Audiophile

Posts: 4382
Joined: October 20, 2000

I'm after a 4v secondary at say 2 amps to feed an AZ1 rectifier using 1.1 Amps.

This is for use in the USA. I'm in the UK where the mains is 230v. It occurred to me I could use a standard 230v into 9v and run it at 115v input. This would only need a tiny dropper resistor as opposed to using a 5v or 6v secondary with larger dropper resistors.

What I don't know is how to rate the VA or how safe this is, since there would be more current through the primary and I don't know if the thickness of the primary wiring would be appropriate.

Can anyone put me straight here?

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RE: Using 230v transformers on 115v primary

PakProtector

18:08:17 10/21/16

RE: Using 230v transformers on 115v primary

Chip647

05:06:22 10/21/16

RE: Using 230v transformers on 115v primary

Johno

06:32:19 10/21/16

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RE: Using 230v transformers on 115v primary

PakProtector

18:08:17 10/21/16

RE: Using 230v transformers on 115v primary

Chip647

05:06:22 10/21/16

RE: Using 230v transformers on 115v primary

Johno

06:32:19 10/21/16

RE: Using 230v transformers on 115v primary, posted on October 21, 2016 at 05:06:22
Chip647 Audiophile Posts: 2651 Location: The South Joined: December 24, 2012	If the secondary is 9 volts at 3 amp, running it at 115v you would have 4.5 volts at the same 3 amps. You will lose the voltage but will not increase the amperage rating for the secondary. Just like running your transformer off a VARIAC at half power, it wont hurt anything if you don't pull more than its rating.

RE: Using 230v transformers on 115v primary, posted on October 21, 2016 at 06:32:19

Johno
Audiophile

Posts: 388
Joined: June 9, 2002

You should be right the (dut) heater as Chip posted will reduce the secondary voltage by 1/2 but the current will remain the same. As the transformer was designed for 50Hz @ now used at 60Hz should be a walk in the park. I sometimes wonder about these so called universal primary transformers regarding freq. Primarily 60Hz universal transformers used at 50Hz may be stressed ?

The lower the operating frequency the more flux lines are generated. Operating a transformer at 50Hz generates 20% more flux lines than at 60Hz. As the number of flux lines approaches the magnetic material limit, the heat in both the transformer core and coil wire increase. This can result in a transformer that exceeds safe temperature levels. Thus, a transformer designed to run at 50Hz will simply run cooler at 60Hz. But one designed for 60Hz only application may overheat if subjected to 50Hz.

Regards
Johno

RE: Using 230v transformers on 115v primary, posted on October 21, 2016 at 18:08:17
PakProtector Audiophile Posts: 12364 Joined: May 14, 2002	Am doing this with dual primary 120/240 to 12V@10A so I can switch between 813 and 4E27's. There is a variac in the primary so I can dial it in at either 5 or 10V. cheers, Douglas Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

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Using 230v transformers on 115v primary

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