[Amps] Large Variac controlling HV power supply

[Dave Trainor]

Is there any disadvantage (other than size) in utilizing a large 30 amp variac to supply the line voltage to the HV transformer in a power supply?    I have a 5000V 3A transformer that came from an industrial induction heater, and the variac from the same to control the voltage. Now both of these are large, but considering a floor roll around unit for the power supply and building the variac into the top with its steering wheel control.  Since I have both the cost is small but is there a disadvantage to doing this power wise? I expect at the current draw for legal limit I should see no voltage sag at all at 3000v since the cycle dyne induction heater the transformer came from was a 10kW unit CCS of course.

Thanks,
David Trainor - N8ZFM