The Method Research Of Motor Discrete Variable Frequency Soft Starting And Harmonic Filtering

The using of electricity promotes the progress of the society and the science andtechnology. As an important transmission equipment, motor also makes greatcontributions to the progress. An integrate method of motor discrete variablefrequency soft starting and harmonic filtering is provided in order to achieve quickand smooth motor starting, to produce high staring torque, to keep the harmonics inpermitted ranges when the motor begins to start, especially with heavy-load. Thismethod combined with variable reactance technique, discrete variable frequencytechnique and dynamic passive harmonic filter technique. It can improve the startingperformance of the motors, save energy, stabilize the voltage of the power supplynetwork, and it also can be realized easily in engineering. What have done andachievements obtained are as follows:Firstly, the topological structure design of discrete variable frequency softstarting and harmonic filtering system is completed. According to the requirementsof the motor starting and working, the design concept of the topological structure hasbeen put forwarded. Analysis and design each subsystem and the whole device. Andalso analysis the ways of working of this system from two aspects of discretevariable frequency soft starting and harmonic filtering. Then make detailedinstructions of its working process.Secondly, the theoretical study of the motor discrete variable frequency softstarting method is completed, including its basic concept and design ideas. And thevoltage divider algorithm is analysed in detail. The traditional discrete variablefrequency soft starting method and the discrete variable frequency soft startingmethod based on the variable reactance converter have been analysed and compared,Through this comparing, the method based on the variable reactance converter hasbeen proved better.Thirdly, the simulation research of the discrete variable frequency soft startingmethod based on the variable reactance converter is completed. Through thissimulation research, the initial angle of the twice fractional frequency, which is thenegative sequence voltage, has been analysed and selected. And combined with the simulation of motor direct starting, the motor discrete variable frequency softstarting with load based on the variable reactance converter is completed. Then hasthe result of every starting data, and it proveds the availability of this method.Fourthly, the harmonic analyse of the discrete variable frequency is completed.Then this analyse has been testified through the simulation research. And a harmonicfiltering method is provided. Its topological structure design and parameter design isalso completed.This study is helpful to improve the starting performance of the motor. Thismethod can successfully control the staring torque and the harmonics, especiallyapplied to the drive equipments in the kiln, coal grinding mill or the mine. And it hasa good significance for practical application.