Staircase modulation applied in a speed controller for small´s single/two - phase induction motors

At present, 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. This paper presents an application for the speed control of a small single/two phase induction motor. This application has a cascaded H-bridge multilevel inverter that is controlled through a staircase modulation. 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. In this paper, a new type of control for angle phase is proposed through the staircase modulation for adjustable speed drive for fractional horse-power single/two phase induction motor. Due to the simplicity of design, the control algorithm it is not necessary to implement it using digital signal processors (DSPs) or microcontroller units (MCUs).