Development of Microprocessor Based Industrial Starter and Slip Regulator of an Induction Motor

1002-1011In this investigation, an attempt has been made to develop a smart and intelligent digital controller to regulate the slip of an induction motor at a desired speed. The overall control and regulation have been provided by controlling the average value of the applied voltage. Besides microprocessor, the hardware consists of three pairs of anti-parallel thyristors connected to three-phase supply lines. An 8085A CPU based microprocessor has been used for sequential, symmetrical and accurate firing and for trigger pulse generation at proper instant. To overcome the loss of synchronism, to eliminate hardware portion appreciably and for generation of a set of six trigger pulses, intelligence of microprocessor has been utilised to calculate the effective trigger angle and deliver trigger pulse in such a way that after delivering a set of six trigger pluses, it finds the particular reference phase which has been used for synchronisation of control circuit with power circuit. For smooth starting, the software has been so developed that the same controller provides reduced voltage starting. The software-based starter, referred to as industrial starter, eliminates the conventional starter. A set of oscillograms giving the speed response of motor has been presented, based on which the developed controller can he recommended over conventional starter