Capacitors in power electronic applications

Asynchronous three-phase motor drives with DC link circuit inverters are emerging as a world standard in industrial and traction applications. Modern power capacitors are essential components of these power converters. New manufacturing techniques and improved designs have enhanced their performance, reliability and quality. Power factor correction capacitors are more and more used in frequently switched equipment with increasing harmonics. Capacitors using liquid impregnation bring risk which cannot be completely neglected. A dry, gas filled capacitor of compact size was developed utilizing modem production methods. In modern inverters, GTO thyristors have substituted conventional power semiconductors. The use of GTOs means that extra attention has to be paid to the RCD protective circuit. This limits the dynamic stress imposed on the thyristor during the critical turn-off phase. Snubber and damping capacitors have to handle high peak/RMS currents and have to be designed for inductance as low as possible