Design And Performance Analysis Of Direct Drive Permanent Magnet Motor For Sand Mill

The existing drive system of sand mill is driven by asynchronous motor plus belt conveyor and reducer.This kind of driving mode has some shortcomings,such as low driving efficiency,serious energy waste,complex structure,serious wear and tear,poor operation reliability and high maintenance cost,which does not meet the requirements of energy saving and environmental protection.In this paper,permanent magnet motor is used to drive sand mill directly,remove belt conveyor and reducer,improve overall driving efficiency,simplify mechanical structure and improve operational reliability.This paper focuses on the design and performance analysis of direct-drive permanent magnet motor around the sand mill drive system,the main research contents are as follows:Firstly,the design parameters of direct-drive permanent magnet motor for sand mill are determined.The motor adopts natural cooling,the design of thermal load is mainly analyzed.Considering the influence of power,speed,material and economy of the motor on thermal load,the thermal load of direct-drive permanent magnet motor should be limited to 1200A/(cm?mm~2).The stator structure,air gap size and rotor structure of the motor are designed.The influence of non-uniform air gap on cogging torque,waveform distortion rate and torque ripple of direct drive permanent magnet motor is studied and analyzed.After selecting the best non-uniform air gap multiple X=2.2,the cogging torque is reduced to 0.83%of rated torque,and the waveform distortion rate and torque ripple are the lowest.The performance of the motor is simulated and analyzed to verify the rationality of the motor design.Secondly,the loss and heat generation rate of each part of the direct-drive permanent magnet motor for sand mill are calculated.Based on the theory of heat transfer,the thermal conductivity and heat dissipation coefficient of each part of the motor are calculated.By establishing the three-dimensional physical model of the motor,the temperature distribution of each part of the motor is calculated.The results show that the temperature distribution of each part of the motor is reasonable,and the highest temperature of the motor winding is107.68?,which can meet the insulation requirements of the F-class motor.Finally,a prototype of direct-drive permanent magnet motor for sand mill is manufactured.No-load and load experiments of direct-drive permanent magnet motor and asynchronous motor were carried out respectively.The experimental results show that the no-load current and no-load loss of direct-drive permanent magnet motor are smaller than that of asynchronous motor,and the current and power of direct-drive permanent magnet motor are obviously reduced under the same load.The temperature rise experiment of direct-drive permanent magnet motor is carried out.By comparing the experimental temperature with the simulation temperature,it can be seen that the error between the experimental value and the simulation value is very small,which verifies the reliability of the simulation.The experiment shows that the temperature of the motor rises to 75.3K,which verifies the rationality of the thermal load design of the motor.The field installation and testing have been completed,and the performance advantages of direct drive permanent magnet motor,such as high efficiency,energy saving and high reliability,have been verified.Both analysis and experiment show that the belt drive and reducer can be removed by using permanent magnet motor direct drive sand mill,which can meet the requirement of sand mill drive system.