ABSTRACT
Large power drives are defined as those drives beyond the reach of low voltage (up to 660V a.c. source) PWM voltage source inverters with IGBTs (and high switching frequency). The two level IGBT-inverter power limit per unit has increased steadily in the last decade to about 2MW (at the time of this writing) by paralleling four 500kW units. With respect to voltage level, we have noted the introduction of 3 to 5 IGBT power cells (diode rectifier plus single phase PWM inverter) in series per phase — properly insulated from each other and to ground — to supply 1MW and more a.c. motors at line voltages up to 4.5kV (rms) [1].
