III. HIGH VOLTAGE HIGH FREQUENCY TEST CIRCUIT
High voltage testing transformer (50Hz), manufactured
by Heafely is used to step up voltage up to 190 kV. The
generation of high voltage was achieved by employing
the resonance phenomenon. The transformer can be used
to test a wide range of electrical equipment such as
cables, terminations, bushings and capacitors. It is
connected to AC-AC rectifier inverter called variablefrequency
drive (VFD) that control the rotational speed
of an AC electric motor by controlling the frequency of
the electrical power supplied to the motor as shown in
Figure 1. In this case, a low voltage HF waveform is
converted to a high voltage field at resonance by tuning
the inductance of transformer to be equal to the total
capacitance at certain frequency. This is achieved by
increasing or decreasing the air gap of movable core.