Variable frequency control of induction motors

ABSTRACT MS THESIS VARIABLE FREQUENCY CONTROL OF INDUCTION MOTORS Suat SARI DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING INSTITUTE OF NATURAL AND APPLIED SCIENCES UNIVERSITY OF ÇUKUROVA Supervisor : Prof.. Dr. Julian RICHARDSON Year:2002 Pages: 79 Jury : Prof.. Dr. Julian RICHARDSON Prof. Dr. A. Hamit SERBEST Assoc. Prof. Dr. Mehmet TÜMAY Variable frequency control of induction motors requires careful analysis for a number of different operational conditions. An induction motor is generally designed for operation on one specific voltage and frequency supply. A variable voltage and frequency supply enables speed control of the motor over a wider range compared to other methods such as voltage or rotor resistance control. It is important that the flux density in the magnetic system is kept at an acceptable level over the range of speeds required. This necessitates a voltage supply whose voltage is approximately proportional to the frequency. The performance of an induction motor over its useful speed range and also its performance at the lower and higher ends of that range is investigated. The current accepted range for a 50 Hz is verified and evaluated as from 10 to 100 Hz, with deteriorated performance at the ends of this range. The particular voltage/frequency source is by Pulse Width Modulation (PWM) control. Keywords: PWM, speed control of induction motors, KURUl*