Estimation of Magnet Reduction in Single-Phase Line-Start Permanent Magnet Synchronous Motor

This paper describes an efficient approach for skillfully guiding the magnet reduction design in a single-phase line-start permanent magnet motor (LSPMM) without worsening motor torque and efficiency performances. The relevant decrease of magnet torque due to magnet reduction is compensated by improving the unique hybrid torque characteristic, that enhancing the balance ratio of reluctance torque to magnet torque. The increased reluctance toque also benefits to motor efficiency performance. Based on an existing LSPMM model, a simulation method, "torque-efficiency map" is proposed to estimate proper reduction of magnet according to assumed saliency ratio. Then, with estimated reduced amount of magnet, a flexible double-layer interior-PM(IPM) rotor structure is optimized with given torque and efficiency constrains. In this paper, the finite element analysis (FEA) combined with equivalent circuit method is used to calculate the LSPMM characteristics and performances. The validity of estimation of magnet reduction based on torque-efficiency map is verified by testing LSPMMs with reduced magnet usage.