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Ed_Dinning · 23rd Oct 2006, 7:53 pm

Hi Mike, you need a variac or a tapped transformer to give a variable source of AC voltage. This should go from near zero to 10/20% above the nominal rating of the transformer in question. Measure volts applied to winding and current flowing into it with no load on the secondaries.
Plot results and you have it.
There may some slight curling at the start of the plot and it should be just starting to form a "knee" at nominal voltage on a good transformer. You can then work out your turns/volt figure for that tranny.

Note that a variable power resistor will not work properly due to phase shifts

This is a good way to do it if you can't remember the formula:

N= V/ 4.44 B F Ae (or you do not know the B value for the lams used)

Ed

23rd Oct 2006, 7:53 pm	#19
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Toroids as O/P trannies Hi Mike, you need a variac or a tapped transformer to give a variable source of AC voltage. This should go from near zero to 10/20% above the nominal rating of the transformer in question. Measure volts applied to winding and current flowing into it with no load on the secondaries. Plot results and you have it. There may some slight curling at the start of the plot and it should be just starting to form a "knee" at nominal voltage on a good transformer. You can then work out your turns/volt figure for that tranny. Note that a variable power resistor will not work properly due to phase shifts This is a good way to do it if you can't remember the formula: N= V/ 4.44 B F Ae (or you do not know the B value for the lams used) Ed