Abstract: A protection circuit for use with an electromagnetic interference filter used in conjunction with a three phase power circuit operating at a particular line frequency includes three capacitors which are coupled to the output terminals of the electromagnetic interference filter. The electromagnetic interference filter and the power circuit have a resonant frequency which is substantially equal to the line frequency. The capacitors of the protection circuit have values which are selected to change the resonant frequency of the electromagnetic interference filter and power circuit such that the resonant frequency is not substantially equal to the line frequency. A protection circuit assembly for use with an electromagnetic interference filter includes a base plate, three ceramic capacitors, three heat conducting substrates, and a protective cover which is mounted on the base plate. The capacitors are mounted on the heat conducting substrates, and the substrates are mounted on the base plate.