Practical investigation of end effect losses in a Motor Integrated Permanent Magnet Gear

This paper presents a practical investigation of the eddy current losses caused by 3D effects in a Motor Integrated Permanent Magnet Gear (MIPMG). Two prototypes of a MIPMG have been designed and build to be used as traction units for an electric vehicle. The measured efficiency of the prototype MIPMGs is superior in urban traffic when compared to state of the art direct drives, even though the measured rotational losses are more than two times higher than estimated with calculations based on 2D Finite Element Analysis (FEA). Based on 3D Magnetostatic FEA, the prototype has been modified to reduce 3D eddy currents in the machine. Material is removed and new parts are made in a non-conducting material. After the modifications of the prototype, the rotational losses have been measured and compared to the earlier measurements and the 2D based calculated losses. The rotational losses have been reduced, thus, making the gap between the measured and calculated losses smaller and increased the efficiency. Assumption regarding unaccounted losses is elaborated, and the presented work makes it possible to make the design of the next generation of MIPMG even better, with lower losses and higher efficiency.