Analysis Of Can Effect And Eddy Current Of Canned Permanent Magnet Motor

Canned motors are widely used in nuclear power,chemical,medical and mining industries as canned pump drives.The canned pump system is leak-free and easy to maintain.The canned motor is characterized by its stator can and rotor can,which play the role of electrical insulation and corrosion resistance in air gap.The stator can is closely attached to the stator teeth inside the stator core,and the rotor can is tightly wrapped around the rotor,which are made of low-conductivity,non-magnetic metal alloy.The magnetic field is alternating in the air gap of the motor.Since the can is a cylindrical integral metal part,eddy current will be induced under the action of the alternating magnetic field,and the loss caused by the eddy current is much larger than the traditional motor losses,which leads to the motor efficiency is greatly reduced.In addition,the emergence of the eddy current on the can will affect the original magnetic field of the motor,thereby changing the internal magnetic field and output characteristics of the motor.Permanent magnet motor has great development potential in the field of canned motors due to its high torque,low loss,and flexible control,and there are few related research literatures.Therefore,in this paper,the finite element method is used to conduct a detailed study and analysis on the can effect of the canned permanent magnet motor and the eddy current on the can.First,the motor design software Speed and Maxwell's RMxprt are used to design a 12-10 permanent magnet brushless DC motor with a power of 3kW.On the basis of which,a canned permanent magnet brushless DC motor is formed by adding a stator can and a rotor can.Finite element simulation model of the motor is established by using Maxwell 2D/3D.Secondly,based on Maxwell 2D,a finite element simulation of the canned permanent magnet brushless DC motor is performed.The harmonic components of the air gap magnetic field are obtained using Fast Fourier Transform,and the effect of can on the air gap magnetic field is analyzed.In addition,the air gap magnetic flux density distribution and harmonic contents of the canned motor under three operating conditions including no-load,rated load,and locked rotor are also analyzed.Then,the losses of the canned motor are obtained through the finite element calculation.The can loss is mainly studied.The effects of changes in can parameters,motor speed and permanent magnet magnetization on the loss of can are analyzed.Next,based on Maxwell 3D,the finite element simulation of the canned motor with only permanent magnet excitation,only winding excitation,and combination of two excitations is performed respectively.The eddy current distribution of the can under three conditions is compared and analyzed.An effective method to reduce the can loss by dividing the can is proposed and verified by finite element simulation.Finally,the canned motor is tested to isolate the can loss,which is compared with the calculation results of the finite element method and the accuracy of the finite element method is verified.There are 64 figures,14 tables and 87 references in this thesis.