Topology Optimization for High Efficiency Design of Permanent Magnet Motor Considering Heat Losses

Abstract

As awareness of environmental problems increases, EVs (electric vehicles) get more attention, and high-performance EVs have been developed. Since motors are one of the components that determines running performance of EVs, many studies have been carried out to improve motor performance. Average torque is often used as an index for evaluating motor performance, and it has a strong relationship with the internal structure. Therefore, structural optimization has been used to obtain the design which can achieve high average torque. Structural optimization is a design method which uses numerical calculations based on mathematical and physical reasons to find a design that maximizes the desired performance, and is applied not only to motors but also to structural design in various fields such as dynamics, heat and fluids. While, in the motor using permanent magnets, the drive generates temperature rising and it decreases the average torque without appropriate cooling. This phenomenon is caused by copper loss which is the loss caused by the current in the coil, iron loss which is caused by changes in the electromagnetic field in the magnetic material, and high-temperature demagnetization which is the property of permanent magnets. Therefore, decreasing heat losses is an important problem in the design of permanent magnet motors to respect with efficiency. In this paper, a design method for permanent magnet motors which minimizes heat losses keeping the torque performance based on topology optimization which is one of structural optimization methods is proposed, and the validity of proposed method is shown with numerical examples.