The Analysis Of Canned Motor With Variable Frequency Speed Regulation And Design Of Control System

Canned motor is a kind of special motor.In recent years,it is the main part of the canned motor pump which is used widely to deliver the combustible,explosive,corrosive and poisonous medium.The main difference between canned motor and the ordinary asynchronism motor is the former has metal can covering the coils.While the motor is running,the magnetic field in air gap cuts the can,which will result in eddy current.The eddy current losses influences on the performance of the motor in some degree.Variable frequency speed regulation is higher efficiency and performance than other control system of asynchronism motor.When the canned motor is powered by frequency converter,many harmonics will result in harmonic eddy current losses in the can.So,some theory analysis and experiment research about canned motor with variable frequency speed regulation and control system will be presented in this paper.Firstly, the equivalent circuit of canned motor is given,based on the equivalent circuit of ordinary asynchronism motor.The harmonic effect on eddy current loss when canned motor is powered by frequency converter is emphatically analysed.A efficient method for the calculation of harmonic eddy current losses is proposed.Using this method,the eddy current losses of a experimental canned motor are calculated.Moreover, the calculated results are compared with experimental results.After the unloaded experiment in dfferent conditions,the comparison with results validated the theoretical analysis.Then, the canned motor mathematical modal under MT rotational coordinate system is deduced.In order to improve the start and speed regulated performance of canned motor, rotor flux oriented vector control strategy is proposed.The whole simulation module is made up by simulink blocks in Matlab environment. Dynamic simulations and experiment results show that the whole control strategy is effective and advantaged.Finally, on the base of theoretical analysis and simulated research, a control system for canned motor is developed on the platform of DSP and IPM.Using this system,some experiment research and part programs are completed.