Speed closed-loop control system based on general-purpose inverter

General-purpose inverters have the characteristic of low price and convenient operation. But they often need a specialized feedback card when feedback closed-loop control is demanded. This results in high cost and limited range of application. This paper considers the problem from cost and precision of constant speed aspects. The authors deal with speed-measuring conversion using an external single-chip processor. Closed-loop speed control can then be achieved in two ways. One is to utilize the process-input port of the inverter and the other is external PID. Therefore the cost of system is cut down and the range of application is expanded