Research On Comprehensive Protection And Rotor Fault Diagnosis Of Electric Motor

Electric motor, especially three-phrase AC motor is widely used in industrial enterprises and agricultural plants, so the subject of motor protection and fault diagnosis are important for motor operation and maintenance staff.The dissertation takes the three-phase AC electric motor as research object and analyses the major fault types of electric motor and its character of electric parameters. The motor protection theory of short current, phase failure, overcurrent, grounding and other faults are studied as well.The motor fault diagnosis technique is researched for detecting the internal fault that cannot be easily identified. The dissertation gives the importance of motor fault diagnosis and its relationship with motor protection. The character of rotor bar breaking fault for electric motor and the technique of stator current monitoring are analyzed. To solve the defect of the FFT spectrum technique, the dissertation deals with the Hilbert-FFT signal processing technique and Neural Network BP Algorithm in detail and the simulation experiments of them are presented. The results obtained demonstrate that the two techniques have good effect and are feasible.A distributed controlling and monitoring system for electric motor based on belt conveying system in Coal Mine is studied. The electric motor protection device takes charge of the motor comprehensive protection. The dissertation gives the hardware and software design, followed by the discussion of implementation of motor protection. The optimal parameters of the inverse-time equation were determined based on the least square fitting technique so as to increase the sensitivity of overcurrent protection which is practicable. As a control node in the belt conveying system based on CAN bus, the protection device also has the function of self-discipline controlling and fault signal sampling when the motor is at an abnormal state. The controlling and monitoring centre, which is a special node, takes charge of distributed monitoring and fault diagnosis. The communication interface design of the system is studied so as to combine motor protection, distributed controlling and fault diagnosis, which is feasible and has extensive application prospect.