Patent ID: 6552510
Filing Date: 2003-04-22
Classification: H02P

Abstract:
A method for controlling a frequency converter having a reference torque, wherein the frequency converter controls a motor and operates torque-controlled partly or entirely in a field weakening region, the method comprising the steps of:defining a direction of travel and sector of a stator flux vector in the motor, defining a voltage vector to be activated for a predetermined active time, said voltage vector following the flux vector, predicting at a time a torque produced by the voltage vector at the end of the active time of the voltage vector, as if the voltage vector was activated at the time of the prediction, comparing the predicted torque with the reference torque of the frequency converter, and implementing a voltage vector change when: i) the predicted torque is smaller than the reference torque and the stator flux vector is moving in a positive direction of travel, or ii) when the torque estimate is greater than the reference torque and the stator flux vector is moving in a negative direction of travel.