Design And Optimization Of A Low-Speed Direct-Drive Switched Reluctance Motor For Mining Applications

A conventional geared-drive system has been used as the drive of Raymond Pulverizer in mining applications.The total efficiency of the system is very low.As energy savers,high efficiency is becoming very significant.Therefore,direct-drive motor systems have become nu-merous attractive appliances.This thesis is targeted to focus on the investigation into a suitable switched reluctance motor for the direct-drive application.This thesis is concerning on the elec-tromagnetic design and thermal analysis of the proposed machine.In the first part of this thesis,proposed a new configuration design of the switched reluc-tance motor for a low-speed direct-drive as for mining applications.The initial design of the proposed machine was calculated by utilizing an analytical method.The influences of individual parameters on the performance of the switched reluctance motor were investigated.Further,the commercial software(package of SPEED)was utilized to carry out the optimization processes of the SRM.The switched reluctance motor performance was studied;also,the switching angle configuration of the proposed machine was investigated.In the second part of the thesis,the switched reluctance motor was optimized based on the surrogate model.The optimization model of a design problem with a single objective,4 constraints,and 4 design variables are presented.The goals of optimization are the maximum average torque,maximum efficiency,and the minimum torque ripple.Meanwhile,the stator and rotor pole arc angle,the stator and rotor yoke thickness,the rotor inner diameter,and the number of turns per pole and the diameter of copper wire are selected as design variables.The surro-gate model of the machine performance was constructed using Latin hypercube sampling and Kriging modeling.The particle swarm optimization based surrogate model techniques is adopt-ed to optimize the switched reluctance motor.A sensitivity analysis was carried out to identify the important independent design variables.The number of significant independent design vari-ables were reduced from 7 to 4 based on a sensitivity analysis.The optimization results were successfully validated using the finite element analysis.The computational cost of the proposed technique of optimizations based on the surrogate model was lower than the conventional opti-mal design techniques based on a finite element analysis.The computation time of the surrogate model required was 5 hr 30 min for an 80 samples of 4 design variables,and the time was taken in the SPEED direct optimization was about 50 hr 7 min.In the third part of the thesis,in the process of electric motor design,it is essential to predict and provide an accurate thermal and mechanical model.An improvement on the thermal and mechanical performance,which was implemented into the proposed switched reluctance motor,is one of the aims of this thesis.A thermal analysis of the SRM requires a deep understanding on the coolant behavior and the thermal mechanism in the motor.Computational fluid dynamics based finite element analysis was carried out to precisely visualize and estimate the fluid state and temperature distribution inside the motor.Several different coolant configurations were car-ried out.The natural frequencies were presented with the developed finite element mechanical structural model for the proposed machine.The cooling jacket configurations with 17 channel-s were found to be optimal for a 72/48 switched reluctance motor.The structure of the shaft with a spoke was proposed for the machine.The advantages of the spoke structure raised the natural frequency and reduced the weight and the temperature of the switched reluctance motor prototype.Finally,The switched reluctance motor prototype was built and experimentally tested.The machine was evaluated in 2D finite element analysis software and validated by experiments.Nu-merical and experimental results show that the switched reluctance motor direct-drive has better characteristics to replace the conventional induction motors in mining applications.The effi-ciency of the whole drive system is found to be as high as 90.19%,whereas the geared induction motor drive provides the only efficiency of 79.13%under similar operating conditions.