The experimental investigation of rotor time constant identification for vector controlled induction motor drives during transient operating conditions

For an indirect vector controlled induction motor drive employing a scheme based on rotor position measurement and inner current loops, the rotor time constant (T_r) is the most influential time varying parameter. Detuning of T_r between the controller and the actual machine leads to suboptimal torque response and inefficient operation. Furthermore the operation of the drive in the field weakening region deteriorates as the voltage ceiling of the inverter prevents correct current control if detuning occurs. In this study, an extension of the reactive power identification scheme is presented and it is shown that the scheme can track the rotor time constant during both changing torque and flux conditions. The scheme is used in conjunction with a rotor flux orientated controller and simulation studies show that the method follows T_r correctly under all operating conditions with a good accuracy. The experimental implementation of the procedure for field weakening conditions is presented