Loss investigation of Motor Integrated Permanent Magnet Gear

This paper presents an 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 MIPMG is superior in urban traffic when compared to state of the art direct drives, even though the measured rotational losses are up to more than 230% higher than estimated with calculations based on 2D FEA. A hypothesis was that large eddy-currents occur in the end-shields of the machine which are made of stainless steel. In order to validate or reject this hypothesis a practical approach is taken by manufacturing new end-shields in a non-conducting material. Measurements of the rotational losses with the new end-shields proved the hypothesis wrong. The results with the new end-shields are verified by 3D FEA and a new hypothesize is made regarding the source of the additional rotational losses.