Heat Transfer and Thermal Design of Finned Frames for TEFC Variable Speed Motors

This paper addresses the evaluation of the heat transfer capacity of a finned frame for different velocities of the cooling fan. As the heat transfer is highly dependent on the air speed and turbulence, separate evaluation is done in four axial sectors of the frame. Each sector is thermally isolated and evenly heated by an internal cylindrical heater with controlled losses. The experimental results allow computing local transfer coefficient on each axial sector, and using these empirical coefficients it is possible to evaluate the thermal capacity of the frame and/or to compute the temperature gradient needed to dissipate certain losses. Based on these results a simple and accurate method to size the finned frame is proposed.