PERFORMANCE ANALYSIS OF A SINGLE-PHASE AC VOLTAGE CONTROLLER UNDER INDUCTION MOTOR LOAD

Abstract

An AC voltage controller is a device that is used to accomplish continuous variation of the rotor speed and rotational force, or torque of an electric motor and the major component of the device are two thyristors connected in an inverse-parallel manner. So, thyristors applications are now rapidly expanding in the field of industrial automation because they are found to consume very little power whenever they are employed to manipulate the flow of electric power. The performance characteristics of thyristorized inverse parallel controller (IPC) under a single-phase induction motor load are presented in this paper. The thyristorized IPC or AC voltage controller is chosen as a cheaper and easier to build controller for induction machines and many more applications such as; induction heating and dimmer. This could save installation and maintenance costs for industries where many variable speed drives are in use. The induction motor stator voltage control is achieved via phase angle control of the AC supply. Performance evaluation of the controller with the motor under different delay angles is demonstrated. Due to nonsinusoidal nature of the controller output voltage, the level of ripples and harmonic contents is studied. As a result of half-wave symmetry in the stator voltage, only odd harmonics is considered in the Fourier based analysis used to investigate the control limits of the controller. MATLAB 7.8 software has been used to simulate the system and its results are compared with the experimental results obtained the laboratory prototype which is found to correlate.