Effect of Temperature on Dielectric Properties of Metallized Film Capacitor

摘要

Metallized polypropylene film capacitors (MPPFCs) are widely used in Modular Multilevel Converters (MMC), owing to its high energy density self-healing capability, and high reliability. However, the impact of temperature on the dielectric properties of capacitors is usually neglected for the existing research. It is significant to investigate temperature effect on dielectric properties of MPPFC, and for more accurate assessment of insulation condition. This work is oriented to evaluate the dielectric performance of MPPFCs by using LCR meter, at the frequencies from 20 to 10^{5 Hz and the measuring temperature ranging from 20 to 160 °C. The variations of characteristic parameters of the capacitance and dielectric loss at different temperatures are compared. The results show that, for lower temperatures (up to 140 °C), capacitance as well as dielectric loss acquires a constant value and does not change significantly. While at higher temperatures (>140 °C) as it approaches its melting temperature, increment in temperature results in a sharp decrease in dielectric constant. Compared with room temperature samples, the capacitance of sample is dropped by 12.5% for 150 °C and 31% for160 °C. It could provide a reference for the accelerate aging test of metalized film capacitor in the MMC converters.}