Capacitor measurements for power electronic applications

Capacitors are utilised in a variety of different ways in power electronic circuits. Typical applications are in snubber, clamping and resonant circuits. For design purposes, it is necessary to make an accurate measurement of the actual behaviour of the capacitance that is added to the circuit under conditions related to those prevailing in a converter. For this purpose, a number of different measurement systems or techniques can be utilised. Four of these measurement systems are compared. These are small signal, variable frequency measurement, large signal quasi-DC measurement, in-situ high voltage measurement and small signal with large bias voltage measurement. Each of these measurement techniques returns characteristic values based on its particular model of the test capacitor. These tests are done on both ceramic and nonceramic capacitors at room temperature. The results are discussed.