Design and Analysis of a Two-Speed Line Start Synchronous Motor: Scheme One

Line-start permanent magnet motors have many advantages, such as high efficiency, high power factor, high power density, and good thermal performances. Also, they do not need to use an inverter in comparison with brushless dc motors. The mentioned advantages have introduced these motors as a good alternative for induction motors in industry. However, there are some drawbacks that limit the use of them. One of these drawbacks is that line start permanent magnet (LSPM) motors could only rotate at one speed due to the fixed polarity of permanent magnets. This matter limits the implementation of LSPM motor for some applications that need two rotating speeds, such as fans and pumps. This paper presents a good scheme that enables LSPM motors to rotate at two different speeds. This scheme is based on combining LSPM motor with synchronous reluctance motor. To validate the proposed scheme, the designed motor has been analyzed by using finite-element method. Simulation results verify the theoretical findings, and show that the proposed scheme leads to good performances at both low- and high-speed operation of the motor.