Study On The Loss Of The Disk Coreless Permanent Magnet Synchronous Motor

Based on the disk coreless permanent magnet synchronous motor(DCPMSM)with axial size is short,compact structure,high power density and high efficiency,therefore,DCPMSM as the core driving force in many areas of equipment,a wide range of applications.Such as the most popular research of new energy magnetic power vehicles,elevator dragging system and ship driving system,etc.But the internal loss of DCPMSM will make temperature rise,and then it will have a direct impact on the permanent magnetic material(Nd-Fe-B),when the temperature is more than curie temperature points,it will cause the irreversible demagnetization of the material,and that leads to the reduction of the overall performance and efficiency of the motor.Therefore,three focus of the paper are as follows:First,the electromagnetic field distribution of the motor is analyzed and calculated.Second,the eddy current loss calculation under different working conditions and driving modes is carried out.At the same time,the waveform,average value and distribution law of the eddy current loss are analyzed.Third,the effective measures for these losses.According to the theoretical analysis in this paper,the three-dimensional finite element model of electromagnetic fields is established.In order to establish a preferred permanent magnet arrangement,the simulation results are compared with those of "Ordinary N,S array","90°Halbach + width arrangement" and "90°Halbach + range width arrangement",it is found that the "90°Halbach + width arrangement" is optimal.Under the condition of no-load and load,the magnetic flux vector diagram and back-EMF waveforms of the disc type motor are solved respectively,which provides the theoretical basis for the next step of eddy current loss analysis and solution.Under no-load condition,the back EMF of the measuring point at free rotation is tested,which is in accordance with the simulation results.Secondly,the windings and the permanent magnets are postprocessed to obtain the mean loss and the waveform of the two kinds of drive modes.The relationship between the mean loss and the rotational speed is summarized.It is proved that the working condition and the driving mode have close relationship with the loss,and also provide a theoretical basis for the following measures to reduce the eddy current losses of permanent magnets.Finally,the eddy current losses on both sides of the rotor disk are analyzed,which are mainly concentrated on the magnetized permanent magnets.The effective measures to reduce this problem are:(1)radial cutting of the axial magnetizing permanent magnet block,the number of cut blocks is 1 to 5,respectively,and the corresponding loss values are obtained.(2)To the axial magnetization of permanent magnet surface mount thin copper plate as a shield.(3)Two effective methods are used in this model.From the calculated figures,tables and data,it can be seen that the radial cutting method and the covering shield method can effectively prevent and transfer the concentrated distribution of eddy currents,and largely reduce the eddy current loss.