CHAPTER ONE
1.1 Introduction
The development of power electronic switches and low cost computational hardware makes AC induction motor drives now compare favorably to DC motors on considerations such as power to weight ratio, acceleration, performance, maintenance, operating environment, and higher operating speed, cost and robustness of the machine, and perhaps control flexibility are often reasons for choosing induction machine drivers in small to medium power range applications [1, 2, 3]. The need for drive system arises due to the constant motion nature of an induction motor. Variable speed drive primarily controls the frequency, voltage, torque and current of a motor, it also controls motor behavior in a unique way. Below is a typical example of variable speed drive system.
Due to the improvement of fast-switching power semiconductor devices and machine control algorithm, more precise variable speed drive method finds particularly growing interest in industrial machines [3].
AC motor drives are widely used to control the speed of conveyor systems, blower speeds, pump speeds, machine tool speeds, and other applications that require variable speed with variable torque [4]. As seen in Figure 1.2 below; the complete system consists of an ac voltage input that is put through a diode bridge rectifier to produce a DC output which across a shunt capacitor will feed the PWM inverter. The PWM inverter is controlled to produce a desired sinusoidal voltage at a particular frequency, which is fed through to the squirrel cage induction motor.
A large variety of methods for Pulse Width Modulation (PWM) exists which are efficient in motor drive. For the AC machine drive application, full utilization of the DC bus voltage is important in order to achieve the maximum output torque under all operating conditions. In this aspect PWM method for the voltage source inverter is implored to feed the induction motor. Moreover sine triangle PWM method produces little current ripple in steady state operation but can be minimized [5].
The speed or torque of an induction machine can be controlled by various control strategies, in this research volt/hertz control of Induction Motor (IM) for both open loop and closed loop systems using a common and efficient modulation strategy known as Sinusoidal Pulse Width Modulation (SPWM) technique, is simulated (using MatLab/Simulink) and compared in both open and closed loop volt/hertz control, and volt/hertz slip difference control showing improved performance of induction motor characteristics. This research work shows the improved volt/hertz method by using constant flux control.
| Project details | Contents |
|---|---|
| Number of Pages | 85 pages |
| Chapter one | Introduction |
| Chapter two | Literature review |
| Chapter three | methodology |
| Chapter four | Data analysis |
| Chapter five | Summary,discussion & recommendations |
| Reference | Reference |
| Questionnaire | Questionnaire |
| Appendix | Appendix |
| Chapter summary | 1 to 5 chapters |
| Available document | PDF and MS-word format |
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