Two positive-side IGBTs (IGBTp)
and two negative-side IGBTs (IGBTn) are switched
alternately. The switching sequences and PWM control
signals are prepared manually with a personal computer
in advance and fed to the memory of a pulse generator
(PG). Then, the inverter is operated according to the
pulse signals from the PG in an open loop and produces
a quasi-sinusoidal current waveform with a frequency of
50/60 Hz and an amplitude of lO A. The switching
frequency of the inverter was 1