COMPARATIVE ANALYSIS OF STEADY STATE CHARACTERISTICS OF THREE-PHASE INDUCTION MOTOR UNDER DIFFERENT SPEED CONTROL SCHEME

Induction motors are the most widely used electrical motors due to their reliability, low cost and robustness. However, induction motors is a constant speed machine; hence it speed control is difficult. Electric drive system is increasingly required to meet the higher performance and reliability requirement of motors used in industrial applications. This work presents different speed controlmethod for three-phase induction motor The steady state equation were written directly from the dynamic equations of the motor based on Parks two-axis techniques. The equations were validated in MATLAB. Amongs the selected speed control methods, the constant voltage frequency (v/f) ratio scheme with peripherial intergral (PI ) controller gave a competitive advantage over others. In this method of constant v/f ratio, by use of rectifier and pulse width modulation (PWM) inverter, the supply voltage as well as the supply frequency is varied such that the voltage and frequency ratio of the motor remains constant and the flux remains constant too. With reference speed of 1500 rpm at diiferent load, results shows that the maximum torque of the motor remains unchanged at different operating zone for various speeds and given load, the maximul torque being 2.2 Nm at steady state opration. The work was done using a three-phase, 4-pole 50Hz, 155 volts induction motor