Thermal management of PQ transformer for a passively cooled power module

In this paper we study the thermal performance of a 5 kW rectifier module experimentally and numerically, with the aim of changing the cooling methodology from an active cooled (fan cooled) to a passively cooled system. Numerical model of the rectifier for fan cooled operation is developed and experimentally validated, following which the critical components in the system are identified. In this system, magnetic components like transformers were observed to have the poorest thermal performance. Given the lack of attention thermal management of magnetic components has received compared to switching components, we numerically study the thermal performance of a PQ 40/40 transformer in a passive (natural convection) scenario. Modifications to the transformer structure were studied and the heat transfer from the transformer was observed to be convection limited (large convection thermal resistance). Providing a minimum resistance conduction path from effective hot spot to ambient was observed to be the best practice. Further, providing a heat transfer path between the coil and core was observed to be crucial to transformer thermal performance.