What factors affect the no-load current of a transformer
How do I find the no load current on a transformer?


Apply rated V , f with no load and measure current.
Primary inductance determines current vs voltage for no load current.   

Do you know how to compute/measure L?
You can expect 3rd and 5th harmonics to rise above rated voltage sharply as core begins to saturate and and inductance geins to drop sharply.

Current source test

Ensure no stray voltage is induced on lines before testing.  The current source is high impedance and prone to noise on this method with low currents.

Try terminating with real load Resistor current and subtract .

Before you can measure EC losses you get  excitation current thus phase and amplitude must be measured. 


For insulation failures they often sweep with expensive Omicron equip. From 0.01Hz to 1 MHz. 


There are written standards for measuring all parameters if you know how to search.

You can use another better transformer to step up voltage using secondary input then measure voltage and current on a scope with a 0.1V current shunt power resistor.