Testing insulation integrity is essential for all high voltage apparatus.
Standard AC test systems have been able to provide a solution for some
applications, but when certain apparatus have much higher voltage and current
requirements a straight AC test system may not be sufficient. In order to limit
input power requirements a resonant test system requires a capacitive test
object and a variable core (variable reactor).
A resonant test system is designed with means to adjust the inductance to
precisely compensate for the capacitance in the high voltage circuit thereby
tuning the system to resonance. The main advantage to this is that very low
(real) input power is required for large output (reactive) power