Using 230V tranformer with 115V

[ZenCow]

Suppose a Euro toroid is rated 200 VA, 230V primary, 2x35V secondaries.
If you used it on US power, e.g. 115V on the primary, what would the secondaries supply?

[wakibaki]

Half the voltage, same current, give or take...

w

[Mikett]

I had thought the potential current would increase but not double because of resistance losses and lowered voltages. The VA rating would by and large remain approximately the same but the transformer would lose some efficiency.

[gearheaddruid]

I think the windings are sized for the current they were speced at at would overheat if you tried to draw twice the current/half voltage through them. There would be an efficiency loss due to the relatively high primary resistance. It will work at half voltage but will not have the regulation of a transformer designed for 120 volts.

[anickode]

It would output half the voltage, but if you were to connect the twin secondaries in series, you could still pull 35 volts from it...

[AndrewT]

halving the mains supply voltage results in half the output voltage and half the VA.