Research On TMS320F2812-Based Soft-Start For Three-phase Asynchronous Motor

The start of three-phase asynchronous motor means the turning procedure of motor from a still state to a state when the speed goes to be stable. The starting current generated by direct starting of three-phase asynchronous under voltage rating is generally4-7times of rated current. Such a strong starting current will not only do harm to grid, but also have negative impact on the starting motor itself. With the development of society, the requirement from all walks of life on the starting efficiency of motor becomes increasingly high. The traditional starting method can no longer meet the needs of the development of modern production since it cannot effectively lighten the rush of starting current to grid. In order to improve the starting efficiency, this paper puts forward soft-starting controlling system of three-phase asynchronous motor which sees high-speed digital TMS320F2812as its controlling core.Soft-starting of motor refers to the use of technical means such as buck, compensation or frequent conversion to achieve smooth starting of motor and mechanical load, reduce the impact of the starting current of motor on grid and further protect grid and the mechanical system of motor. The main circuit of soft-starting is an ideal starting method adopting adjusting circuit constituted by three opposite-parallel thyristors, which can adjust the starting current and starting torque. Also, soft-starting possesses the advantage of being energy-saving.In this paper, SIMULLNK toolbox of MATLAB simulation software is used to construct a simulation model of the soft-starting system of a three-phase asynchronous motor. This model conducts a simulation research on the controlling method of the soft-starting by adopting PI to adjust the firing angle of the thyristor. The simulation result of this experiment suggests that such soft-starting system can effectively lighten the rush of starting current of a three-phase asynchronous motor to grid.Based on the experiment above, the paper finishes the design of hardware circuit of soft-starting controlling system of DSP three-phase asynchronous motor, taking TMS320F2812from TI company as its master chip. Also, peripheral circuits includes the main circuit, detection circuit, drive circuit, the protection circuit and three-phase imbalanced correcting circuit and so on.Finally, the software design of this soft-starting controlling system is completed in CCS software programming environment, including initialization procedure of DSP system, the design of signal acquisition, handling procedure, the sub-procedure of soft-starting and the procedure chart of some software modules.