الفهرس 
mathematical analysisOnly 14 pages are availabe for public view
 |  | from | 143 |  |  |
| | | from | 143 | | |
Abstract
The use of induction motors for variable-speed industrial drive applications has always been a valuable suggestion. The induction motor, often the best choice among AC machines for many industrial tasks, is simple and best in construction. In this thesis a technique for induction motor speed control is illustrated. This technique uses switched capacitors to replace resistors in the rotor side.The speed control is accomplished by controlling the switched frequency of the capacitor. An experimental system is built and tested for motor performance and operation. This method provides a mean of speed control which is simple and continuous. It is well suited to electronic control using any suitable electronic circuits. Many researches have focused on speed control of slip ring induction motors by switched capacitor in rotor. Abdel Fattah, El-Deep , Amin and El-Nahry studied in [1] the speed control of the slip ring induction motor using a microprocessor to drive a power transistor switched capacitor circuit on the rotor side. The steady-state performance of this motor is studied in [2]. A dynamic model is developed to study the open loop and closed loop drive performance , also theoretical and experimental results for the transfer functions - V - for the switched capacitors wound rotor induction motor are obtained in [3,4]. The frequencies and the magnitudes of the transient current and toque in addition to the effect of the varied values of capacitance on the different conditions of transient at starting is illustrated in [5]. This system is applied to a slip ring induction motor and the speed control is accomplished using microprocessor as discussed in [6] . In this work this system is applied to a 4 hp slip ring induction motor. The torque-slip characteristics are deduced mathematically and compared to the experimental one and they were in good agreement at chosen frequency. Also the harmonic contents in the stator current and in the rotor current are analyzed. An open loop control system of the motor speed is performed. The 8051 microcontroller was employed to provide the necessary control signal frequency. - VI - The thesis is composed of 6 main chapters : - The first chapter is an introductory review for the methods of speed control of induction motors. - The second chapter introduces the mathematical analysis of the system and the Pspice simulation of the switching circuit. - Chapter (3) studies the power electronic switches. - The fourth chapter introduces the 8051 microcontroller interfacing circuit, the design and construction of the switching circuit and the software for generating the control signal using the 8051 microcontroller. - In chapter (5) the experimental work, test results and harmonic analysis of the stator and rotor currents are given. Also the experimental torque-slip characteristics are measured at 30% of full-load torque. The results are compared with that mathematically obtained.The last chapter is devoted to the conclusions and the future works.