Research Of The Fractional Slot Single-Layer Winding Reverse-Salient Permanent Magnet Synchronous Motor

The reverse-salient permanent magnet synchronous motor(PMSM)has broad application prospects in electric vehicle,electric spindle,flywheel energy storage and variable speed power generation systems due to its advantages,such as a small size,light weight,high power density,wide constant-power speed range,low noload back EMF,high permanent magnet(PM)operating point and weak short-circuit(SC)current.To solve the problem that the conventional PMSM magnetic field is difficult to be adjusted,a fractional slot single-layer winding reverse-salient PMSM with wide constant-power speed range is studied.The basic research work is also carried out on its d-axis and q-axis current control method,target-oriented design method,SC characteristic and main performance.Based on maximum torque per ampere(MTPA)control,flux weakening(FW)control and maximum torque per voltage(MTPV)control,the current control method of the reverse-salient PMSM is studied.The results show that when the reverse-salient PMSM is operated at or below the rated speed,the d-axis current is flux-intensifying current,and the magnitude of the flux-intensifying current is related to saliency ratio and d-axis inductance.When the reverse-salient PMSM is operated above the rated speed,the flux-intensifying speed region is also related to the saliency ratio and d-axis inductance.The current control methods of PMSM with different saliency ratios are compared and analyzed in the full speed range,and the current control laws of the reverse-salient PMSM are obtained.By analyzing the influence of current control method and electromagnetic parameters on torque and power,the influence laws of electromagnetic parameters on torque and constantpower speed range are summarized,which provides a theoretical basis for precise design and high-performance operation of the reverse-salient PMSM.At present,the conventional design method lacks consideration of the reverse salient PMSM characteristics,which requires to be repeatedly checked and revised,and the design time is long.To address this problem,a target-oriented design method of the reverse-salient PMSM is investigated.The reverse-salient PMSM targetoriented flow and its design method of electromagnetic,structural and winding parameters are given.The relationship between design indexes,structural and winding parameters are established with design indexes as the input parameters,electromagnetic parameters as the intermediate variables,structural and winding parameters as the output variables.The reverse-salient PMSM design is completed with the goal of minimizing volume.The reverse-salient PMSM model is established by finite element method(FEM),and is optimized by genetic algorithm(GA),which is compared with the target-oriented design method.A prototype is designed and manufactured,and its no-load back EMF,electromagnetic torque and constant-power speed range are tested.The accuracy of the design method is verified by the FEM and prototype experimental results.The research on the SC current variation laws of the reverse-salient PMSM and the rotor topology of short-circuit current suppression method is carried out.The influence of saliency ratio and d-axis inductance on no-load back EMF is analyzed,and the methods to reduce no-load back EMF are summarized.By the simulation and analyzing of the winding terminal SC and the interturn SC,it is verified that the reverse-salient PMSM has stronger SC current suppression capability.Specifically,as the reverse-salient PMSM winding terminal is short-circuited,the SC current is smaller than the conventional IPMSM.As we analyzed winding interturn SC of the reverse-salient PMSM,the inductance parameters of interturn SC are calculated by equivalent magnetic circuit method and the laws of SC current varying with the number of SC turns are obtained.Based on the comparative analysis of the magnetomotive force harmonic distribution and self-inductance of fractional-slot single-winding and double-winding reverse-salient PMSM,the reasons for the strong SC current suppression capability of fractional-slot single-winding reversesalient PMSM are explained.The influence of rotor topology on SC current is studied according to the equivalent magnetic circuit,and the low SC current rotor design principle is obtained,which provides theoretical support for proposing a rotor topology with low SC current.By analyzing the influence of the d-axis inductance,saliency ratio and internal power factor angle on the power factor,the characteristics of the power factor of the reverse-salient PMSM are described,and the laws of the reverse-salient PMSM power factor with the speed is revealed.Based on the comparative analysis of the influence of reverse-salient PMSM and conventional IPMSM current control methods on copper loss,the copper loss characteristics of reverse-salient PMSM are described,and the laws of copper loss with the d-axis inductance and saliency ratio are revealed.The efficiency of the reverse-salient PMSM is calculated and measured by FEM and experimental method.Based on the simulation and experimental results,the efficiency characteristics of the reverse-salient PMSM are discussed,which lays a theoretical foundation for the design and efficient operation of the reverse-salient PMSM.