Thermal mitigation for high energy density metallized polypropylene capacitors when repetitively discharging

High energy density capacitors with metallized polypropylene film are now available from 1-3 Joules/cc depending upon duty cycles and the lifetime required. As the energy density increases, the operating voltage approaches or exceeds the breakdown strength of the dielectric film. The polypropylene film dielectric strength is in the range of 550 to 720 volts per micrommeter.¹ A low energy self-healing is desired for these types of capacitors so ultra-thin vacuum deposted aluminum metal is employed for the electrodes.