Over temperature protection in power module for hybrid and electric vehicle

In hybrid electric vehicle(HEV) and electric vehicle(EV), the thermal characterization of power module is important feature for the performance and reliability of inverter. A three phase inverter of PWM switching method generates the power dissipation of conduction and switching losses in IGBTs and diodes. This power dissipation, depending on the magnitude and frequency of phase current, DC-Link voltage and modulation index, cause an increase of junction temperature(Tj). It is required that the Tj should not exceed defined limit, irrespectively of various driving conditions such as high speed driving, regenerative braking, and hill-holding. In this paper, the power loss calculation and the thermal model for a three phase PWM Inverter is developed to estimate the maximum junction temperature within various driving conditions. With the predicted junction temperature, a HEV/EV is safely protected from overheating and be guaranteed its lifetime. However, the proposed thermal model is no longer valid in abnormal conditions such as lack of water or current sensor failure, so NTC, a temperature sensor inside of power module, is additionally needed to operate the power devices as long as the max allowable junction temp has not over passed the limit.