A Lumped Parameter Thermal Model for Single-Sided AFPM Machines With Experimental Validation

Axial flux permanent magnet (AFPM) machines are promising for hybrid electric vehicles (HEVs) due to the compactness, high torque density, and high efficiency. However, poor thermal characterization leads to an oversizing of these machines, which ultimately compromises overall system efficiency. In this article, the transient thermal behavior of all the components in the single-sided AFPM machine is characterized in an accurate but computationally efficient lumped parameter thermal model (LPTM). For the first time, contact measurements on the rotor have been used in AFPM machines to demonstrate the ability of the model to predict all component temperatures within 4 degrees C for steady state. The mean temperature error over a load step transient was less than 5 degrees C with a maximum error of less than 13.5 degrees C that was for the winding. The model has a running time of approximately 1000 times faster than real time on a desktop machine and is suitable for integration into system simulation tools and predictive control strategies to avoid oversizing of the motor and improve the usage of the electric machine in dynamic duty cycles.