| Due to the uneven processing level and the complex operating condition,the motors do not operate very well in practice.The wide range of use and different operating conditions make it important to monitor the condition of the motor and detect faults.At present,the traditional monitoring methods have more or less limit,and it is difficult to obtain more accurate monitoring results without affecting the normal operation of the motors.Therefore,the operating condition monitoring of the motor based on stray flux has important theoretical significance andengineering value.The main accomplished work and obtained results in this paper are as follows:(Ⅰ)Analysis of air-gap field and stray flux in induction motors.A method that can resolve the air gap magnetic field and stray flux of a motor is proposed.Use turn equation and winding function to derive the magnetomotive force generated by the motor stator and rotor current,and write the mathematical expression for the magnetomotive force.Calculate motor slot reluctance and complete the subdivision of the air gap reluctance.The magnetic circuit diagram of the motor is drawn to obtain the distribution of air gap magnetic density,so does the coilmagnetic chain and coil voltage.Combined with attenuation model,considering the stator yoke,machine housing and air as the transmission medium,and the transmission process of air gap magnetic field is an attenuation process.Calculate the attenuation coefficients of each part and obtaining the analytical result of the stray flux of the prototype on the basis of the analytical results of the air gap magnetic field.(Ⅱ)Establish the finite element model to verify the analytical results of air gap magnetic field and stray flux and build the experimental platform.Build a 2D simulation model of the motor by JMAG,simulation result of air gap magnetic field,coil chain,coil voltage and stray flux of the motor are obtained by setting appropriate parameters.The analytical results have great agreement with Finite Element Analysis,the analysis method is proven.Complete the analysis of stray magnetic field in case of motor failure.Establish an experimental platform for the detection of stray flux,including prototype,dynamometer,load,high sensitivity magnetic field sensor and data acquisition card,and write Labview data acquisition program and display interface.(Ⅲ)Research on induction motor speed identification,torque identification and fault detection based on stray flux.Use the established platform to collect the stray flux data of different rotational speeds and the identification of torque is done by finite element simulation.Then,collect the stray flux of the motor with electrical failure.By Fast Fourier Transform,analyze the spectrum of the stray flux signal.And finally,compare the spectral characteristics of the fault condition with those of the healthy condition to identify the electrical failure. |
