Voltage Derating Behavior of High Temperature Capacitors for DC-Link Applications

Abstract:
New high temperature capacitors made with recently introduced high-heat polymer film, ELCRESTM HTV150, are shown to operate at higher temperatures reaching 150deg C with little derating of applied voltage. At 130deg C the operating voltage is only slightly reduced to 95% of the rated voltage at 105deg C. At 150deg C the operating voltage remains considerably high at 86% of the rated voltage; thus, maintaining high voltage performance over a broad temperature range. By comparison, the rated voltage for typical polymer film capacitors, e.g., capacitors made with polypropylene (PP) or ethylene propylene norbornene (EPN), is reduced by as much as 50% when the temperature reaches 125deg C for PP, or reduced by about 45% at 135deg C for EPN. Such reduction, or voltage derating, must be compensated for by increasing the thickness of the polymer film used in the capacitor to maintain the voltage withstanding ability over the operating temperature range. Capacitors made with HTV150 film pass 2000-hour reliability life testing at the elevated temperatures and rated voltage with stable capacitance, dielectric losses, and insulation resistance. Such capacitors are well positioned for use in the AC-DC inverters in DC-link modules operating at high voltages and temperatures reaching 150deg C for efficient operation in electric vehicle applications.