Research On Dsp-based Soft-start Control System For Asynchronous Motor

Soft-start is a new technology which is developing very fast in modern times, the main circuit usually use thyristor to make the voltage regulator circuit, the starting current and starting torque is adjustable, it has a prominent performance in the protection of transmission system and maintenance of power quality, so the soft-star is an ideal starting mode.Firstly, this paper introduces the development of the AC motor soft-start technology, analyses the start process of motor in theory, and then base on comparing the characteristics of start modes in comprehensive to propose the soft-start method, and describes the main circuit of soft-starter which is thyristor-based .Then researches about the soft-start control strategy of the asynchronous motor, applies the SIMULINK toolbox in MATLAB to build a simulation model of asynchronous motor soft starter system which is based on AC voltage regulation method. Study the process of direct starting and soft starting by application of the simulation model of the asynchronous motor ,the simulation results are compared and analyzed.The hardware of the asynchronous motor soft start control system is DSP-based, use the TMS320F2812 as the main control unit, the external circuit includes the main circuit, detection circuit, driver circuit, protection circuits and unbalanced three-phase correction circuit.Finally, the software of the control system is completed in the CCS3.1 software environment. Including the main program, synchronous signal interrupt service routine, trigger driving signal interrupt service routine, soft-start algorithm subroutines and so on, parts of the software modules are gived the program flow Fig.The hardware circuit is debugged, the system is running normally, the closed-loop control method of the thyristor voltage and power factor angle can effectively limit the starting current and torque, improve the starting performance and have a good start effect.