Significance of isolation impedance in a solid-state power modulator

Effects induced by isolation capacitance were studied in a solid-state pulsed-power modulator for an induction synchrotron. Parasitic isolation capacitors in DC power supplies to drive switching elements have large effects on the operational performance of a high-repetition-rate power modulator. The isolation capacitor deteriorates the flatness in output pulses by increasing the total capacitance in the modulator circuit. It is predicted by a circuit analysis that the isolation capacitor causes an electrical breakdown of the switching element. These effects have been confirmed experimentally. It was found that the most promising way to fix this problem is to reduce the isolation capacitance. By sufficient reduction, the solid-state power modulator has been operated at a repetition rate of 1 MHz in the continuous wave mode without any serious effects induced by the isolation capacitors.