An Analytical, Numerical and Experimental Study on Demagnetization Phenomena in Permanent Magnet Line-Start Machine

It is very important to improve the parameters of the electric motor in order to improve its performance. One of the ways to improve the performance of electric motors is to use permanent magnets in the structure of induction motors. These types of motors are known as line start motors. The use of permanent magnets eliminates ohmic losses and increases efficiency. Due to the fact that permanent magnetism plays the most important role in these motors, the smallest change in the magnetic properties of the used magnet will cause malfunction of the machine. One of the important phenomena that changes the properties of the core magnet is the phenomenon of demagnetization. Although this phenomenon has very destructive effects on engine performance, the design of electric motors is still done without considering this issue. In this article, a line start motor is designed. The numerical simulation results show that the performance and efficiency of the motor in the demagnetization mode are significantly reduced. Also, the increased current in demagnetized motors causes a further decrease in the magnet's magnetic properties. This effect is progressively repeated many times until the property of the applied permanent magnet is lost. Finally, an analytical model was presented for examining and designing electric motors, considering the effects of demagnetization. The results showed that the use of the analytical model of motor design considering the effects of demagnetization can be a suitable alternative to the use of conventional methods in the design of electric motors.