Research Of The Magnetizing And Demagnetizing System For 2MW Permanent Magnet Wind Motor

In recent years,with the improvement of NdFeB permanent magnet comprehensive magnetic properties and preparation technology,its application range is becoming more and more extensive,which puts forward higher requirements for the magnetizing and demagnetizing device.Especially for direct-drive permanent magnet generator in the field of wind power,due to its single pole size is large,so the traditional magnetizing and demagnetizing methods are to disassemble a single magnetic pole into a small piece of magnetic steel for magnetizing and demagnetizing,and then assemble them,this method are not only low efficiency but bad for generator rotor assembly.Therefore,this paper proposed a new method of integral magnetizing and demagnetizing of single magnetic pole of 2MW wind turbine based on pulse strong magnetic field,and demonstrates this method through pulse magnetizing and demagnetizing experiment,finite element calculation and structural design.Firstly,several existing magnetizing and demagnetizing technologies were investigated and compared in this paper,and pulse magnetizing and demagnetizing methods had been selected according to the magnetic characteristics of NdFeB permanent magnet materials with high coercivity.In order to study the feasibility of this method,the finite element model was established and the simulation analysis of the magnetizing and demagnetizing process was carried out according to the size of the N35 NdFeB sample.Meanwhile,a complete set of experimental platform for pulse magnetizing and demagnetizing was built,which including pulsed discharging circuit,coil and residual magnet measurement system.Through simulation analysis and experimental exploration of these two ways,the pulsed magnetizing and demagnetizing method was verified to be feasible,and the pulse magnetic field distribution for saturation magnetizing and complete demagnetizing of NdFeB permanent magnet had been found.At the same time,the magnetizing and demagnetizing curves of the permanent magnet materials obtained by simulation and experiment were compared by fitting,and the applicability of the finite element model in the process of pulsed magnetizing and demagnetizing was verified.For the entire 2MW wind turbine rotor monopolar magnetizing and demagnetizing system,the two-dimensional and three-dimensional finite element simulation model were established,which include the circuit,magnetic field,temperature field and structure field.Based on the experimental results of magnetizing and demagnetizing,J-A hysteresis curve parameters of NdFeB permanent magnet material was set in the FEM model to accurately reflect their magnetizing and demagnetizing characteristics.Through simulation calculation,this paper analyzed the pulsed current,magnetic field configuration,coil temperature,electromagnetic force and other physical parameters in the process of pulsed magnetizing and demagnetizing.The feasibility magnetizing and demagnetizing system for whole single pole of 2MW wind turbine was verified.Based on simulation and experimental results,the system design and structure optimization of single-pole magnetizing and demagnetizing system for 2MW wind turbines were carried out,including coil framework design,wire size and winding mode selection,coil reinforcement device design and reliability verification,mobile platform design of magnetizing and demagnetizing device,and the overall assembly process of the system.Through the above series of experiments,simulation and design,the studied 2MW motor magnetizing and demagnetizing system was proved to be fast,high efficiency,and lowenergy cost,which was of great significance for the development of large permanent magnet motor magnetizing and demagnetizing system.