High Speed Motor Magnet

High Speed Motor Magnet

In recent years, the application of permanent magnet (PM) synchronous motors in electrical vehicles has increased rapidly. This is mainly because PMSMs can achieve higher speeds than conventional AC induction motors. However, the high speed operation of PMSMs poses more challenges in electromagnetic design, thermal management and mechanical structure. In order to improve the efficiency and power density of PMSMs, a number of techniques have been developed. These include optimizing the iron core loss, improving the magnetic induction intensity and harmonic components of different positions in the iron core, reducing the copper consumption by adopting the toroidal winding structure, and minimizing the number of turns on the end winding.

The most important challenge in the development of high-speed PMSMs is to reduce the rotor iron core loss. For this purpose, various measures such as adjusting the stator slot opening width, optimizing the pole-slot fit, using a slant slot and a magnetic slot wedge have been proposed [1]. However, these methods can only weaken the eddy current losses in the rotor but cannot fully reduce them. In addition, they require complex and expensive control systems.

Another important issue is to improve the stability of PMSMs at high speeds. For this purpose, the use of non-contact bearings is an effective solution. Among these, air bearings and magnetic levitation bearings are the most promising. In comparison to ball bearings, these non-contact bearings can support the rotor at a much lower mass and can operate under higher speeds. Nevertheless, their cost is still prohibitive.

To further reduce the rotor iron loss of PMSMs, it is necessary to optimize the installation parameters of the permanent magnets. This can be achieved by applying a new method for analyzing and optimizing the eddy current distribution of the magnetic circuits. This method uses a combination of the finite element model and a simplified physical model. The resulting model is suitable for calculating the temperature field of a double-layer V-type HSPMM under a variety of conditions.

In contrast to previous research, which focuses on changing the rotor and stator structures or the cooling mode to lower the operating temperature of the HSPMM, this method does not require any structural changes. It also focuses on reducing the copper and iron loss by modifying the installation parameters of the permanent magnets. Moreover, the results of this method have been verified by comparing the electromagnetic models of the HSPMM with those of the ETCM. As shown in Fig. 7, the converge accuracy between FEA and MEC is above 0.95, which means that this method can save a lot of times in the electromagnetic calculation process of HSPMMs. Additionally, the converged accuracy has also been verified with the experimental results of a test model. These results indicate that the ETCM method and the temperature field optimization method proposed in this paper are reliable and efficient.

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