The Problem of Rotor Eddy-Current Losses in a Permanent Magnet Motor with High Power Density

Abstract

The article presents the problem of eddy-current losses in rotor elements of a permanent magnet motor with high power density. These losses can cause excessive heating of the rotor components and even demagnetization of the permanent magnets. The subject of the analysis is a motor weighing about 10 kg and a maximum power of 40 kW at 4800 rpm. It is a fractional slot, three phase, synchronous motor with the number of magnetic poles 2p = 20. In the paper, particular attention was paid to the correct selection of the number of stator slots to the number of magnetic poles, which affects both the value of the obtained electromagnetic torque and the value of eddy-current losses in the rotor elements. Several variants of the armature with a different number of slots in the stator were analyzed. The causes of rotor eddy-current losses and also suggestions for their minimization were discussed. The main goal of the works is the selection of the optimal solution of the motor’s electromagnetic circuit, taking into account the previously defined objective functions.KeywordsHigh power density motorsEddy-current lossesPermanent magnets