Efficiency analysis of a 42- pole/54-slot fractional-slot concentrated-wound interior permanent magnet synchronous machine

Fractional slot-concentrated wound interior permanent magnet synchronous machines (FSCW- IPMSM) display high power density and high efficiency due to the short stator end windings and absence of rotor windings. The purpose of this paper is to analyze the efficiency of a 42-pole/54-slot FSCW-IPMSM under three commonly used current reference trajectory control algorithms namely zero direct axis current control(id = 0), maximum torque per ampere (MTPA) control and loss minimization (LM) control. Analysis of the experimentally measured efficiency shows that loss minimization control is not as effective as it is in the distributed winding IPM machines. A possible reason for this is that additional rotor losses that are caused by the harmonics of the magneto motive force (MMF) of the FSCW stator are not accounted in the LM control technique. It considers stator core loss due to the fundamental flux only. LM control shows an improvement of efficiency in partial load of FSCW-IPMSM. The analysis of the paper is based on test results conducted on a 4kW prototype FSCW IPMSM.