Research On Soft Start Of High Voltage Motor Based On Multiplex And Switch Transformer

With the continuous development of the national economy,the continuous expansion of the scale of production in all walks of life,as the main power source of the industry,the use of large motor is becoming more and more common.In the starting process of high voltage and large capacity motor,in order to avoid the voltage of single thyristor is not using thyristor series pressure caused the soft start by switching transformer soft starting structure to solve the high voltage motor,aiming at the problem of soft starting stator current harmonics of high voltage and large capacity motor,will introduce multiple technology to soft start technology,to reduce harmonics of stator current,the motor starting current is more close to the sine wave,reduce the harmonic pollution to the power grid caused,prolong the service life of the motor.Firstly,the short circuit bridge structure is used instead of the traditional anti parallel structure.For one thing,the soft starter with the rectifier bridge structure has the advantages of simplifying the circuit structure,saving the switch and the line,and the soft starter is more convenient to isolate the power network.for another,rectifier bridge structure can be output by the phase-shifting transformer,a plurality of positive and negative output rectifier clockwise polarity connection,making it easier to achieve multiple soft start and rectifying bridge series can improve the working voltage and power level device.Secondly,through the start of the high voltage motor directly,the traditional anti parallel thyristor soft starter,soft starter switch transformer and rectifier bridge improvement on the structure of these two kinds of soft start and were introduced in two kinds of improved soft starter based on the structure of the series three technology of soft starting of the simulation,the simulation results show that the short circuit bridge structure with anti parallel thyristor structure with the same starting characteristics,and comparing various motor starting modes of maximum starting current and starting time,electromagnetic torque,stator current harmonic distortion rate starting index,the switch transformer series three heavy soft start to meet defined starting current can be reduced at the same time,large scale motor stator current harmonic distortion rate,reduce the harm caused by the power grid,the motor torque,and the impact is also greatly reduced.Finally,the hardware design and software design of the soft start control system are introduced.The hardware design includes the main circuit,the voltage synchronous detection circuit,the isolation drive circuit,the resistance capacitance buffer circuit.The software design mainly includes the main program flow chart,the ramp voltage soft start subroutine flow chart,the voltage synchronization examination flow chart.