Device Loss and Thermal Characteristics of High Power PWM Converters

Thermal limit of a power electronic converter such as voltage source converter is essentially determined by the thermal limits of the individual devices such as insulated gated bipolar transistor (IGBT) and diode. Thermal limit of each device is its maximum junction temperature. The device junction temperature depends on the device loss and thermal equivalent circuit of the device. This paper attempts to correlate device loss and junction temperature on one hand with the operating conditions of the converter (i.e. kVA loading, power factor, dc bus voltage and switching frequency) on the other. The device loss characteristics and junction temperature characteristics are evaluated theoretically for a high-power pulse width modulated voltage source converter. The theoretical calculations are validated on a heat-run test set-up, consisting of two identical converters with circulating power arrangement.