Comparison of Performance of Induction Motor and Line-Start Permanent Magnet Synchronous Motor—the State of the Art

The line-start permanent magnet synchronous motor (LSPMSM) is a combination of an induction motor and a permanent magnet (PM) motor. In this motor, due to the presence of a magnet and the resulting braking torque, the starting torque is reduced. Increasing the resistance of the rotor bars increases the starting torque, but it reduces the synchronizing ability of the motor. Due to concerns about energy scarcity and global economic challenges, the world is urged to save energy. One effective way to address these problems is to increase the energy efficiency of electrical devices. Since electrical machines account for about 45% of all industrial electricity use, improving the efficiency of electric motors can save a lot of energy. Induction motors are popular in the industry, because they are self-start, are cost-effective to produce, and are easy to maintain. However, despite improvements over time, it is still a challenge to overcome some inherent limitations of induction motors, such as their relatively low efficiency and power factor. As a result, global electric motor manufacturers are gradually focusing more on alternative electric machine technologies to meet stricter energy efficiency standards. One technology that has received a lot of attention is the LSPMSM. This type of motor is especially appealing because it is self-start and has high efficiency and power factor. Researches on LSPMSMs mainly focus on developing rotor configurations, creating steady-state analytical models, and applying the transient time-step finite element method for synchronization assessment. The torque mechanisms in transient starting and steady-state operating conditions differ in LSPMSMs because their rotor includes both an induction cage and PM.