CLOSED LOOP PERFORMANCE OF INDUCTION MOTORS WITH CONSTANT VOLTS/HERTZ CONTROL

ABSTRACT

Characteristics of a closed loop induction motor drive, supplied from a variable frequency voltage source, and operating under constant volts/hertz control are presented. The motor linearized equations in the synchronously rotating reference frame are used to analyse the drive dynamic performance. It is shown that this performance can be greatly improved by including a properly designed speed controller in the drive structure. Thus, the decrease in stability, associated with the open loop motor operation is eliminated and the resulting drive gives satisfactory performance over the entire input frequency range. The experimental results, which confirm the validity of the motor dynamic model are also included.