[Splint]

Hi All,
I'm having a little difficulty with a transformer I recovered from a photocopier. It appears to have two primary windings and when I put 240 volts to either of the windings the circuit breaker trips out and cuts the power supply. Both circuits appear to be ok, not shorting to ground or any signs of failure. The only logical thing I can think of is that the insulation on the primary windings has failed and it is shorting. The secondary winding is open circuit, is that an issue? Anyone have any comments?

Cheers
Splint

[Al_The_Man]

Would it be that the two primary windings are 120v in parallel or 240v in series?
If that were the case then you may be applying 240 to a 120v winding?
BTW if you connect the primaries in parallel they have to be phased correctly if they are not marked as to the respective winding start and end.
Al.

[Splint]

Thanks for the tip Al, I tried what you suggested but to no avail, it then occoured to me that the design intention of the coil may have been to have a cooling fan in the primary circuit so I gave it a try and it appears to be working just fine...

Thanks again.
Spint

[Al_The_Man]

I think what you have done is simply limit the current in the primary if the fan is in series with the winding, You will not be able to achieve maximum power from the transformer with this kind of load in series.
If the transformer is not faulty then with the correct voltage applied to the primary, you should not need a series load for it to work.
Al.