Rapid prototyping tool for a fuzzy logic based soft-starter

Abstract

On account of the problems associated with the conventional starting techniques (DOL, Star-Delta, etc.) an efficient method of soft-starting is required with energy saving features and adaptive parameter setting capability. An optimal soft-starting is one that starts the motor with minimum voltage and reduced starting current limit (CURLIM). Starting current limit is different for motors of different ratings and for the same motor under different initial load conditions. Fuzzy logic has been adapted with a triangular membership function with a finite overlap between two membership grades to achieve the adaptive parameter setting capability. It features automatic setting of current limit and the optimality is achieved by performing the task with appropriate settings for a maximum firing angle (/spl alpha//sub max/), decrement of /spl alpha/ (/spl Delta//spl alpha/) and the delay time between the two successive decrements (/spl Delta/t) calculated based on 'fuzzy logic'. The hardware interface is developed around an '8051 microcontroller based rapid prototyping tool' which interfaces the personal computer (PC) with the external world through its serial communication link. This tool improved the ease with which a prototype algorithm could be developed. All the algorithms are tested on different motors in the laboratory under different load conditions and found to be reliable and optimal. In all, a novel fuzzy logic based soft-start scheme for AC chopper fed induction motor drive is proposed and implemented using a rapid prototyping tool.