Accurate Measurement of Key Parameters of Film Capacitors for EV Power Control Unit

Abstract

This paper will introduce the accurate measurement of key parameters of a film capacitor for electric vehicle (EV) power control unit (PCU), i.e. its capacitance (C), parallel resistance (Rp), equivalent series resistance (ESR) and Equivalent series inductance (ESL). These parameters will be analyzed how to affect the capacitor life and thus the life of EV PCU. Firstly, the LCR meter tester was used to test the film capacitors, but it fails to measure ESR and ESL accurately because they are too small. So, a testing method is developed to detect these parameters of the film capacitors. The test method is mainly based a function generator, a power amplifier, current sensing resistor and a 16-bit, 2MS/s/ch A/D card. The acquired data are processed through Fourier Transformation (FT) to get the accurate amplitudes and phases of both the current and voltage of the tested capacitor. The experimental results show that the developed method provides a reliable procedure to measure the characteristics of film capacitors, which can be also used to monitor the health of the film capacitor online.