Newbie and having problem

Hi guys,
I have a toroid transformer where the input is 230 VAC and it has 2 output each one rated at 40 VAC. Can I feed the 40VAC part with 230VAC and get >1 Kvolt output?

No!

It may be visually entertaining for about 1 or 2 seconds, but the end result will be a destroyed transformer.

JimB

If anything, the insulation between the windings and across the transformer gap will be rated for 240V use. You put a voltage up the output and get a few kV at the input, the first thing that will blow will be the isolation

you will also find the transformer primary has a significantly higher inductance than the secondary which will limit the input current. Put a voltage up the output and that inductance will be a lot lower, so the current will be higher... so the bang will be bigger

I agree that the insulation won’t be rated at higher voltage, but it’s difficult to know at what voltage it will break down.

The magnetic core of any mains transformer will be running near saturation when running at its rated voltage and frequency. The manufacturer wouldn’t waste material to have more core than needed.

The result is that applying too much voltage to one of the windings will saturate the core and the inductance will be reduced, so the current will be large. However, at higher frequency it will take more voltage to saturate the core. The relationship is linear, so at twice the frequency, it will take twice the voltage to saturate the core.

Increasing the frequency will increase the eddy current heating in the core, but most toroidal transformers have ferrite cores, so the heating at high frequency wouldn’t be as much as with a laminated core.

The insulation is likely to be the limit if you can increase the frequency.

Arnold Maynard said:

Hi guys,
I have a toroid transformer where the input is 230 VAC and it has 2 output each one rated at 40 VAC. Can I feed the 40VAC part with 230VAC and get >1 Kvolt output?

Click to expand...

before I say don't do it, please tell us how you plan to use the 1kv+ voltage. Do you need Ac voltage? Maybe we can help you solve your problem and achieve your goal in another way. Some wonderful trickery can be used to achieve high voltage AC or DC with 5 to 12VDC power supplies.

Diver300 said:

. . .
Increasing the frequency will increase the eddy current heating in the core, but most toroidal transformers have ferrite cores, so the heating at high frequency wouldn’t be as much as with a laminated core.
. . .

Click to expand...

Most high frequency toroids are wound on ferrite cores, but low frequency (50, 60Kz) toroids usually use tape wound cores. Effectively the same laminate structure as an E-I transformer, but made from a long strip of iron rolled up like a roll of tape.

Arnold Maynard said:

Can I feed the 40VAC part with 230VAC and get >1 Kvolt output?

Click to expand...

you could, but like people have said it's not recommended... the insulation on the 40V winding might not be able to handle 230V, and the insulation on the primary side, although made to withstand surges and spikes of 1kV or higher, is not likely to last very long with such a high voltage continuously.