48 The Research of Cascade Speed-Adjusting System of Induction Motor Based on Digital Control

The chopper cascade speed-adjusting device is a kind of energy saving product of speed performance and cost-effective, which has been widely used in AC speed-adjusting. The main circuit topology is introduced and the working principle is analyzed of the AC motor chopper cascade speed-adjusting in this article. Chopper control makes the system power factor improved. The IGBT is selected as chopper switching device instead of thyristor chopper, which improves the speed performance of the system and overcomes forced commutation shortcomings of the SCR. Also, the line is simple and the control is convenient. The TMS320LF2407A DSP processor of TI is used as the main control chip to realize the digital control of chopper cascade speed-adjusting system, the system's hardware and software diagram are showed, and the experimental result is acquired in this paper. The result shows that the system runs reliably and the desired effect is achieved.