Certain investigations on speed control of three phase squirrel cage induction motor

Abstract

In these contemporary days, the enhancement of power electronics and the three-phase induction motor plays a dynamic role in the industrial applications. Moreover, the attributes such as rugged structure, high reliability, low cost, high efficiency, robustness, economical and wide speed range are the primary aspects of the convenience, but induction motors do not characteristically have the competence of variable speed operations. However, the current augmentations in speed control techniques of the Induction Motor (IM) have prompted to their substantial scale usage in all virtual electrical drives. As affiliated to the speed control techniques, there are two chief control strategies called scalar and vector control which are performing an imperative job. Out of the different strategies for speed control, constant V/F control which is a scalar control technique is equipped for regulating both speed and torque viably. Subsequently, scalar control cannot be connected successfully for regulating frameworks with dynamic behaviour whereas, the vector control performs the main role which permits the decoupled analysis where the torque and the flux components can be independently controlled. With the progression in the semiconductor fabrication technology, switching power converters are employed in an ever-increasing number of motor drives to adapt and distribute the essential energy to the motor. Amidst the regularly practiced methods in static three-phase inverters for direct current to alternating current power conversion, Pulse Width Modulation (PWM) is prominent. The most typical PWM technique is the sinusoidal PWM (SPWM) technique. Space Vector Pulse Width Modulation (SVPWM) is a technique of pre-computation of switching the timing instants for various sectors of target output. This target output is achieved by prospecting the position of the active vectors per sampling interval. Despite the fact that the space vector pulse width modulation affords the real necessities of the motor drives and suites the recent speed control technique, complex computation and grouping of harmonics around a particular frequency are unacceptable. On the whole, conventional deterministic PWM techniques afford a PWM waveform with a large fundamental voltage component with low order harmonics stifled. The harmonic power is generally focused in the high-frequency range as a result of highfrequency switching of the power inverter. Though these high-frequency harmonics can be filtered effortlessly by an inductive load, their presence is a cause of Electro Magnetic Interference (EMI) and the acoustic noises. Because of the deterministic switching frequency PWM of the inverters, the motor produces a hostile acoustic noise and vibration. Inappropriately, the insignificant harmonic voltages are regularly focused at the integer multiples of the predetermined switching frequency. newline