Reluctance Torque Utility for Line-Starting Permanent Magnet Motors

This paper presents two types of prototype line-starting permanent magnet motors for compressor drives; one is a nonsalient-pole machine, and the other is a salient-pole machine. It is proved through both the analyses and experiments that the utility of reluctance torque not only boosts steady-state characteristics but also line-starting capabilities. It was also noteworthy that the salient-pole machine in the steady-state operation could achieve not only better efficiency but also a higher power factor. Finally, the designed motors achieved a 4% to 5% increase in efficiency over all operational points, which prevented a rise in temperature by 30 K, compared with a conventional two-pole induction motor. The results are given for a two-pole prototype motor with P_N = 5 kW, n_N = 3000 min ^-1, V_N = 200 V, and Y-connection.