Abstract
In the vector control system using the slip frepuency control method, the rotor resistance of an induction motor is used for calculating a slip frequency. So that the change in temperature of the rotor resistance causes the deterioration of the torque control characteristic. This paper presents a new method of the compensation for the rotor resistance change which is robust for the stator resistance change. A Current control loop is composed of the γ-δ axes in which the γ axis is coincident to the stator current. In this method, the stator voltage error on the δ axis which is directly obtainable from this current control loop was used. The change in the stator voltage was able to be detected accurately, therefore the torque control accuracy was improved particularly in the low speed region. The experimental results of the current response and the compensation for the rotor resistance deviation were shown, too.
Moreover though the mutual inductance has been treated as an invariable value, the value does change by a frequency and an excitine command. In this control method, an initial tuning of the equivalent mutual inductance was achieved by detecting the deviation component of the stator voltage on the δ axis at the no load running condition. Furthermore in the region with the constant power where the field weakening control was achieved, the excellent experimental results of the compensation for the deviation of the equivalent mutual inductance were shown.
