Soft-Starter Design Of High Voltage Induction Motor

The three phase induction motor is most used in industry,agriculture,daily life and etc ., because of its simple structure, stable running , and lowerprice. With the quickly development of modern industry, the more excellentstarting performance is desired. Direct starting of medium or big inductionmotors results in high current surge. The current will endanger the safty of themotor and drop the system voltage and influence the running of motors in it.Some devices are used to reduce the voltage applied the terminal of the motor atstarting, such as Y/Δstarter autotransformer, water resistance, magneticreluctance etc. But these methods have their limitations , and the limitationsreduce the application of the methods. With the development of power electronictechnology and modern control theory, thyristorized soft starters have rapidlydeveloped. Experts at home and abroad and scholars have done a lot of work inthyristorized soft starters ,and it is the time to develop practical device and it haswide market prospect.This paper has done in-depth research on the principles of thyristorized softstarters used for induction starting, including the principles of AC voltagecontroller and reduced voltage starting and has done some research on themodern control theory , and the good performance of the thyristorized softstarters in theory is described in the paper. Simulation mode is established usingthe MATLAB/SIMULINK, and the simulation has been done for the slopevoltage starting and constant current starting. The result of the simulation provesthe corretness of the theoretical analyses.The implementation scheme is given for the problem of heavy load startingof induction motor using thyristorized reduced voltage starting.Basic principle ofthe scheme is presented in the paper ,the simulation and the low voltageexperiment are given in the paper and the result proves the correctness andvalidity of the implementation scheme.This paper has designed the device of thyristorized soft starters appropriatedfor practicality application. The device has many kinds of starting mode to startinduction motors under various environmental conditions, the devive also has soft stop and more than ten kinds of protection methods for the device itself andthe induction motors. Control system , hardware system and software system arestated in the paper , hardware electrocircuit and software flowchart are stated inthe paper too. Low voltage and high voltage experiments research have beendone , and the results prove the advantages of good performance and steadyoperation of the device.