Adjustable frequency single phase induction motor driver for low supply voltage starting

Proposed drive circuit successfully alleviates the problem of starting a single phase induction motor when supplied by low driving voltage. Motor fails to start when the voltage level sinks to a value below 65% of rated driving voltage for single phase induction motor. As a result, no counter electromotive force generates; eventually large input current flows through the winding causing intensive heating and insulation fracture. In the proposed driver circuit, this problem has been encountered by a microcontroller based automatic adjustable output frequency inverter circuit which is capable of increasing or decreasing output frequency as per desired to any fraction or multiple of supply frequency of 50 Hz. Smooth Frequency control has facilitated the motor to run at constant voltage frequency ratio, which mollifies the starting problem when supplied by a low driving voltage. The circuit has been practically implemented and performance on a single phase induction motor driven pump has been observed. The result strengthens that proposed drive circuit is conspicuously effectual for induction motor starting at persistently fluctuating voltage pattern.