Induced pole rotor structure for line start permanent magnet synchronous motors

This study presents a rotor structure, for a line start permanent magnet synchronous motors (LSPMSMs), which can be applied to other types of inverter driven motors, such as brushless dc and permanent magnet synchronous motors. In this development, the magnet configuration is a combination of both circumferentially (spoke) as well as radially magnetised (embedded) magnets which are so arranged that induced poles are generated in alternate positions in the heteropolar structure, thereby reducing the quantity of permanent magnets in the rotor. Both the transient as well as steady-state performances of the machine have been analysed by using time-stepping finite element method. For experimental demonstration a prototype which uses spoke magnets (P1), plus two prototypes (P2 and P3) of the proposed magnet arrangement have been built. The former (P1) is used for benchmarking the performance of the proposed configuration. Results have indicated that the rotor configuration reported here (P2) with reduced magnet volume gives better performance than the spoke magnet rotor LSPMSM. Also, the performances of prototype LSPMSMs are compared with that of the standard induction motor of the same frame size and physical dimensions.