Calculation Of Equivalent Circuit Parameters And Analysis Of Electromagnetic Torque For Doubly Skewed Rotor Induction Motor

Induction motors play an important role in industrial drives,and its performance standards have improved with economic development.Special skewed rotor induction motors are the structural modification of conventional skewed rotor induction motor,aiming at avoiding the disadvantages of conventional skewed rotor induction motor such as axial drifting,and improving the related performances of induction motor.Compared with the conventional skewed rotor induction motor,some previous literatures have shown that these special skewed rotor induction motors can greatly reduce the slot harmonics of air-gap magnetic flux density,thereby reducing the vibration and noise of the motor.The other performances of these special skewed rotor induction motors have not been paid much attention by researchers.This paper will take the doubly skewed rotor induction motor as an example,a finite element method for calculating the equivalent circuit parameters is proposed.Then,the electromagnetic torque performances are analyzed in depth based on the equivalent circuit parameter model.This paper will be researched in depth from the following aspects:1.Firstly,the significances of analyzing the equivalent circuit parameter model of induction motor is expounded.Then,aiming at the fact that the equivalent circuit parameters of doubly skewed rotor induction motor cannot accurately calculate by the traditional algorithms,a finite element computational method suitable for calculating the equivalent circuit parameters of all special skewed rotor induction motor is proposed,and an experimental method for calculating the equivalent circuit parameters of induction motor is proposed.Finally,the results of traditional algorithms,the results of finite element method and the experimental results are compared to verify the effectiveness of the proposed method.2.In this paper,the three-dimensional(3D)finite element models are needed to be established when using the finite element method to calculate the equivalent circuit parameters and electromagnetic torque of the doubly skewed rotor induction motor.The common characteristics of skewed rotor induction motors will be taken into account in the finite element models,such as the inter-bar currents and magnetic axial variations in saturation,as well as the skin effect of rotor bars.3.The principle and process of calculating electromagnetic torque by virtual displacement method and equivalent circuit parameter method are analyzed theoretically.The calculation results of equivalent circuit parameter method and virtual displacement method are compared with the experimental results.The advantages of the equivalent circuit parameter method proposed in this paper in calculating the electromagnetic torque of the special skewed rotor induction motors can be obtained from the comparison results.4.The electromagnetic torques of the conventional skewed rotor induction motor,the doubly skewed rotor induction motor and the doubly skewed rotor induction motor with middle ring are calculated by the equivalent circuit parameter method.Compared with the theoretical analysis results,it is concluded that the doubly skewed rotor induction motors can improve the starting torque and maximum torque of the conventional skewed rotor induction motor.For skewed rotor induction motors,both the theoretical analysis and the simulation results show that the harmonic torque can be minimized by a suitable skewed angle,thereby their electromagnetic torque performances can be improved.In this paper,the equivalent circuit parameters and electromagnetic torque of doubly skewed rotor induction motor are systematically studied.Based on the theoretical analysis,the finite element simulation results and the experimental results,it is shown that the computational methods and analytical thinking presented in this paper can provide reference for the research of electromagnetic torque performances of special skewed rotor induction motors.