The Fault Model And Diagnosis Of Electric Machine

With the development of modern science and technology, electric machines play a more and more important role in modern industrial plants. The risk of machine failing can be remarkably reduced if normal service conditions can be arranged in advance. In other words, one may avoid very costly expensive downtime of plant by proper time scheduling of machine replacement or repair if warning of impeding failure can be obtained in advance.This paper analysis two normal faults of the stator and rotor parts, and builds its math model. The main faults of the stator's is the fault of the stator resistance, it is mainly caused by the faults of destroy its insulation. The faults of the rotor is caused by continual startup and overloading running, this makes the rotor enduring big stress, little by little it causes the fault under this conditions. These two faults can be revealed through the change of it's resistance, and based on this we have set up the motor's fault model.In this paper first discuss the development, the present condition and the vary fault diagnosis methods of electric motor. And then builds the fault model of the three-phase asynchronous motor on the basis of the six-class accurate mathematics model in the stillness coordinate, that is the fault model of the electric motor. And this model is aimed at the fault of the stator and rotor's. And the acquiring of the fault eigenvector is observed through on-line identification.This paper makes an in-depth study into the working principle ofthe EKF(Extended Kalman Filter) arithmetic. It sets up the state observation of the asynchronous motor which is based on the EKF, combined with decision-making of the Bayes, it carries through theory analysis on the fault of the stator and rotor, emulating and experiment study. By the analysis we can see the approach is very effectively to fault detection, isolation and estimation of rotors and stators .In order to verify the truth of the fault model, an indirect method is used. It is because the change of stator's resistance affect the stator's voltage and current directly, the experiment is designed to detect the voltage and current under normal and fault condition to reflect the state of stator's resistance. Also in the experiment we obtain the current by measuring the lead current from transducer to the motor, and this because it is the same current with the stator. And through the test we found the effect is very perfect.In the end, we conclude the advantage and disadvantage of this method, especially point out the exiting problem, and corresponding to that we give out the reasonable improvement methods and the solving scheme. And expectation to the future this arithmetic will be applicated into practice by the high performance digital signal processor (DSP)'s development.