Speed adjustment of an induction motor drive using eddy current braking

number: 
11
English
Degree: 
Author: 
Firas Abdullah Thweny Al-Saidi
Supervisor: 
Dr. Q. A. H. Naman
Dr. Fa'iq J. Al-Azzawi,
year: 
1995
Abstract:

The work in this thesis presents an application of eddy current brakes for speed control of motors. This technique can be used independently for speed control, or in corporation with the other standard techniques to achieve greater degree of flexibility. The present technique is applicable to ac motors and prime movers. Basically) the proposed scheme is a small capacity eddy current brake relative to the size of the motor. A small torque is constantly applied to the machine by the eddy current brake. This torque is not to exceed a small percentage of the rated motor torque. By varying this torque according to speed fluctuations, the system performance against such fluctuations can be improved and better speed accuracies can be achieved. In this work, it is intended to improve the system performance by applying a small torque to overcome positive and negative speed fluctuations. The theoretical work is presented for the case of an eddy brake with rectangular electromagnets and nonmagnetic rotating disc. The motor under test is a two horsepower, 383 Volt, 50 Hertz, and a four pole induction motor. To verify the theoretical work, experimental work is being carried out on a setup with the above specifications. A personal computer built around an 8088 microprocessor is used to control the system by adjusting the brake in accordance with speed fluctuations using a PWM dc chopper and a PID algorithm as a speed controller. The performance of the system is evaluated by making several tests on it. The tests showed encouraging results in terms of efficiency and reliability.