Abstract
Vector control techniques of induction motors are based on either the slip frequency control or the field orientation control. As for characteristics, it is well-known that the former is subject to sensitive influences by thermal variations of the secondary resistance while the latter maintains robustness by means of flux detection even if parameters vary. Both methods aim to regulate separately the flux and the torque of induction motors. There is, however, a little difference in the characteristics of the slip frequency type and the field orientation one. The incomplete equivalence between two methods brings about the different properties.
The slip frequency controlled induction motor does not refer to flux detection or calculation as it is called an indirect method, whereas it suffers the implicit defect that the actual rotating filed is not observed directly.
The authors propose that a flux oriented torque control be introduced even in the indirect method. This paper describes the new vector controlled induction motors using feed forward and feedback controls.
The proposed system has a feed forward controller for quick response brought by the existing slip frequency control and a feedback controller for robustness which is provided by the field orientation.
The feed forward and feedback controlled induction motors are free from degradation in torque generation caused by the thermal variation of the secondary resistance.
