Hi. I've lurked for a while, but this is my first Q.

I have two identical transformers, each with twin primaries. They have the standard arrangement for 230/115 series/parallel operation.

(I plan to use both transformers in the same supply.)

I would like a simple way of switching from 115V to 230V operation. Do I essentially need a series/parallel switch for each transformer to do this?

Looking at one transformer at a time: If I have the pair of primaries in series, where they join is essentially a centre tap. And if I use just one primary for 115V, I can expect the power rating to be halved, right?

So if halving the power in 115V mode is not a concern, instead of a full series/parallel switch, I could simply switch the mains lead from the centre tap to the other end of the (previously unused) primary, right?

Here's my question: If I use both transformers at the same time, would it matter if the "centre taps" of each transformer are permanently connected to each other?

 

I think you're confusing the issue by using the two transformers?.

Parallel the 115V windings of the two transformers together, this effectively gives you one transformer with two 115V windings. Put then in parallel for 115V or series for 230V.

I would also strongly suggest you make the change internal, or some idiot will set it wrong and blow the transformers!.

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CHeers.

Was planning to simply have a two hole terminal block inside so you could just switch the active wire from one place to another, but I think I'll actually put a switch inside for series-parallel.


Thanks again.