25-09-2010, 11:31 AM
SPEED CONTROL OF SYNCHRONOUS MOTOR BY USING VARIABLE FREQUENCY DRIVES
ABSTRACT :
A novel open-loop speed control method for induction motors that provides high output torque and nearly zero steady-state speed error at any frequency is presented. The control scheme is based on the popular constant volts per hertz (V/f) method using low-cost open-loop current sensors. Only stator current measurements are needed to compensate for both stator resistance drop and slip frequency. The scheme proposed fully compensates for the current±resistance (IR) voltage drop by vectorially modifying the stator voltage and keeping the magnitude of the
