Design and Implementation of Constant Speed control System for the Induction motors Using Programmable logic Controller (PLC) and Variable Frequency Derive (VFD)

Abstract This paper presents an automatic speed control system on three phase squirrel cage induction motor using Programming Logic Circuit (PLC) and Variable Frequency Drive (VFD) techniques. The aim of this study is to obtain a constant speed of induction motors when these motors are exposed to variable loads. The required speed of the induction motor can be set as a numerical value by (PLC), while the actual speed of the induction motor can be measured by a tachometer which is equipped with (PLC) ) Through an Analog to Digital Converter (ADC). Then the two speeds are compared to the set point with minimum error to get the required constant speed. The control system designed to be tested with two stator poles number (two and four poles) of induction motors. The results have cleared that in spite of doubled the load 11 and 8 times respectively, but the yield average shaft speeds are almost constant 2891.15 rpm and 1402.45 rpm respectively.