Temperature rise and free convection heat transfer coefficient for 2-D pot-core inductors and transformers

This paper presents calculated results for the surface temperature rise and free convection heat transfer coefficient in the case of a vertically oriented pot-core inductor or transformer for which the total loss is known. The average surface temperature rise and convection heat transfer coefficient are shown to primarily depend on two characteristic parameters: the height of the core and the average convective heat flux dissipated from the side surface. In fact, simulations illustrate that only the side surface of the core effectively dissipates convective heat and the contribution of the core top surface to convection is negligible. The heat transfer due to radiation is also calculated from the average surface temperature rise. It becomes apparent that the radiative heat transfer is in the same order as the total convective heat transfer. A generalized equation is developed to correlate the temperature rise and total loss for pot-core components of the same height. In addition, through an experimental example, we show that the analysis for pot cores produces high errors if applied for ETD cores.