A novel speed controller for single/two-phase fractional horse-power motors

The widespread use of small induction motors for home appliances and other applications justify the development of new drives and motor designs. The aim shall be to save energy and to consume it with a clean absorption of current from the mains. The basis of the system proposed in this paper is to generate sinusoidal waveforms using digital techniques (they are stored in an EEPROM as reference vectors). These waveforms are composed to obtain a 2-phase voltage system, with variable amplitude and frequency, to feed small electric power drives. The two parameters of the waveforms-amplitude and frequency- in the motor are easily regulated and amplified by means of semiconductors working in PWM mode. This new drive provides advantages as a straightforward control method, simplicity of the design, easily regulated starting torque and its low cost. As a whole, the design leads to a robust, compact, cheap unit, easy to manufacture.