Design and implementation of a variable frequency drive for single-phase induction motor

Variable frequency drive of single-phase induction motor can have many potential advantages, like reduced inrush current during starting, high starting torque, possibility of higher efficiency, more tolerant to variation in grid supply voltage etc. Many of the existing electrical gadgets use single-phase induction motor of capacitor start / capacitor-run type. A typical example is the motor used in household refrigerators. In this application the starting torque requirement is high. It will be good if the motor starts with reduced inrush current and if the amount of cooling by refrigerator is controlled by variable speed operation of the motor. This work proposes a power electronic circuit which can be incorporated with some change in the existing wiring circuit of the refrigerator.