Testing Heatsink Faults in Power Transistors by means of Thermal Model

In safety-critical systems, power electronics is widely used, e.g., for driving actuators. High currents and high voltages are often used in power electronics, which may cause considerable heating of the power devices. Hence, different mechanisms for heat dissipation and cooling of power devices are adopted. An excessive temperature increase in the power devices may lead to considerable electrical and mechanical stresses, and overheated electrical devices are subject to more rapid ageing. Therefore, an incorrect behaviour of the dissipation system can seriously damage or even block a safety-critical system. Hence, it is necessary to introduce test mechanisms to check the correct behaviour of the heatsinks. In this paper, we propose a strategy to quantitatively evaluate the effectiveness of a test for the dissipation system. The proposed approach is based on an electrothermal model of the cooling system. It allows one to identify the maximum size of the thermal fault tolerated by the dissipation system before the electrical device break down.