Rotor time constant determination of induction motor drives via steady-state torque analysis

The paper presents a simple and straightforward way to calculate the rotor time constant of an induction motor by analysing the steady-state electromagnetic torque. The main advantage of the proposed approach is its simple implementation. Moreover, it can be performed either off-line, as a tool to calculate the rotor time constant of an asynchronous motor, or on-line, to tune a field oriented control (FOC) drive. The only constraint is that a constant load is required during the calculation procedure that a takes few seconds. This is not a problem in laboratory measurements, in a large number of applications in which the load is strictly related to the speed, nor in servo-drives where constant load operation are usually scheduled during the working cycles. A theoretical development of the new rotor time constant calculation procedure is given, followed by a validation of the procedure by means of simulation and experimental tests