Study on voltage maintaining performance of metalized film capacitors under high electric fields

The metalized film capacitor can work under a high electric field due to its self-healing characteristic. But when the capacitor is charged rapidly to a specified high voltage (under a high electric field) and then it is disconnected from the power supply, a significant voltage drop will be observed, so the capacitor energy efficiency will reduce. It can be observed that the general curve of the voltage decay has a rapid initial drop and then the curve can usually be fit to a pure exponential. Firstly, this paper analyses the factors which cause the voltage decay through experimental study. The research results show that electric field strength, operating temperature and hold time play important roles in the voltage decay process. The higher the electric field or operating temperature is, the more significant the voltage drop is. If the voltage of the capacitor is maintained for a specified period of time, the voltage drop will reduce significantly. Through these experimental results, it is revealed that the voltage drop is mainly related to leakage and polarization. So the insulation resistance at various temperatures under high electric field is tested by the special technique. The results of insulation resistances are consistent with the voltage decay at various temperatures. Moreover, the interfacial polarization which exists in the charging process of metalized film capacitor is discussed. The interfacial polarization causes the rapid initial voltage decay.