Modeling, Analyzing And Designing Of Surface-Mounted Permanent-Magnet Synchronous Machines

Surface-mounted permanent magnet (PM) synchronous machine has been widelyused in many engineering applications due to its small volume, high efficiency andhigh torque density advantages. It is a kind of energy-saving motor with greatpotential. Analytical models of magnetic field and electromagnetic performances arebuilt in this paper for surface-mounted permanent magnet synchronous machines, inorder to investigate the effects of design parameters on performances. Furthermore, anexperimental prototype machine is designed and analyzed.Magnetic field calculation is an important step and prerequisite for PMsynchronous machine design and analysis. However, too many design variables aremutual cupling for the machine with sator slotting, which increase the difficulty toobtain the mapping relationship between design parameters and performance. Ananalytical model is presented in this paper which combines the advantages ofmagnetic equivalent circuit (MEC) method and scalar potential analytical method, andprovides a useful and quick tool for predicting the open-circuit magnetic field withstator slots and teeth. It reudece the difficulty of magnetic field modeling by introducethe approximate magnetic air-gap model and condisering the distributions of statorslots and rotor poles separately, and is used to investigate the effects of stator slottingon magnetic field, back-EMF and electromagnetic performances.Cogging torque is one of the emphases and difficulties of PM synchronousmachine research. In order to reduce the cogging torque, auxiliary slot method isemployed to the conventional surface-mounted PM synchronous machine structure,and a cogging torque general model is built for the improved machine by usingsubdomain model. Based on the analytical model, influence of auxiliary slot opening,depth, numbers and position on torques and back-EMF performances are furtherinvestigated. For PM machine with any auxiliary slots distribution, the analyticalmodel can accurately account for the interactions between winding slots and auxiliaryslots as well as their finite depths and obtain its cogging torque waveform.Magnet poles are pivotal parts in PM synchronous machines, but the magnet poleparameters are always hard to determine in PM motor design. In order to solve thisproblem, an analytical method based on subdomain model modified by discrete ideaand superposition principle is presented to predict the magnetic field, cogging torque, back-EMF and electromagnetic torque of PM synchronous machines withuneven-thickness magnet pole. The effects of magnet pole parameters on motorbehaviors are discussed and particle swarm optimization (PSO) algorithm is appliedto the pole shape design. Results show that the optimized uneven-thickness magnetpole can perfect magnetic field distribution, decrease harmonic content of back-EMF，reduce torque ripples and improve performances of the motor.Based on the above theoretical analysis conclusions, a low-speed, high-torque11kW PM synchronous machine is designed in this paper. The basic structures andparameters of the machine are determined with consideration of it application andrequirments. Then, the detailed electromagnetic paremeter design and FE simulationare completed based on computer-aid design method. Finally, the mechanicalstructures are designed and the prototype machine is fabricated. Experimental tests arecarried out and verified the correctness of the design method.