1- AC variable speed drives have large capacitors connected across the DC link as indicated in below. After a VSD is switched off, a period of several minutes must be allowed to elapse before any work commences on the equipment. This is necessary to allow these internal capacitors to fully discharge. Most modern converters include some form of visual indication when the capacitors are charged.
2-Capacitor banks used for power factor correction are particularly vulnerable. They
present a low impedance path to high frequency harmonic currents. These increase the
dielectric losses in the capacitor bank, which can lead to overloading and eventual failure.