FEM Analysis On Eddy Current Losses In The Permanent Magnets And Its Influence On The Machines' Performance

Because of the magnetic field which is built by permanent magnet, permanent magnet synchronous motor (PMSM) has simplified structure and low cost for its machining and installation. Besides, the operational reliability has also been improved. Benefiting from the absence of the exciting current and the excitation loss, the efficiency and the power density have increased. Mostly, the permanent magnet is NdFeB material, which has relatively high temperature coefficients of remanence and coercivity and a moderate electrical conductivity. The eddy current induced in permanent magnet often lead to heat when the external magnetic field is time-varying. So it is necessary to calculate and analyse the eddy current in rotor and to find solutions.Several subjects in relation to the eddy current field in NdFeB magnets of PMSM and its influences on the performance of the motor are covered. The contents are summarized as follows:The development and application of PMSM are briefly reviewed. The background as well as the status of the research on the calculation of magnetic field in PMSM is highlighted.According to the characteristic of the eddy currents in magnets, the governing equations of the two-dimensional eddy current field and the three-dimensional eddy current field are respectively established. Magnetic vector potential is adopted to calculate the magnetic field and eddy currents as unknown function in two-dimensional. And A ,φ?A method is used in the three-dimensional. In the analysis, the motion effect is considered.Based on the actual structure of disc type permanent magnet synchronous machines, the magnet field of the machine and the eddy current in the rotor are solved by two-dimensional finite element method (FEM). The calculation is carried out under the condition of load and no-load, respectively. It includes the eddy current caused by the teeth of the stator and the different eddy currents under different running speed conditions. After solution, the magnetic vector potential waveforms and the eddy current waveforms are drawn according to the result data, and distribution figures of the eddy current losses are also obtained. Some influencing factors on the eddy...