A single/two-phase, regenerative, variable speed, induction motor drive with sinusoidal input current

The single-phase induction motor with two windings, main and auxiliary, is probably the most widely used motor in the world. The mains operated single-phase motor usually operates at low power factor, low efficiency and at fixed speed. At most, two or three fixed speeds are provided when required, through manual intervention. Such fixed-speed operation hinders product designers from incorporating many interesting and useful features in their products. The present concern on harmonic pollution of the supply and low power factor operation, as embodied in the recent IEC555-2 standard, also calls for power factor correction measures to be included in applications where a single-phase motor is used. This paper presents a variable speed single-phase motor (with two windings) drive that utilises just six switches as found in the emerging intelligent power modules. Just one integrated module with six switches serves to implement the input rectifier with sinusoidal input current, and the two-phase VSI or CSI inverter to drive the two phases of the motor with balanced ampere-turns. The input rectifier is also reversible, so that the motor can be braked with energy return to the mains, thus operating with high efficiency at all times