Parameter estimation of inverter and motor model at standstill using measured currents only

Methods for the estimation of the parameters in the electrical equivalent diagram for an induction motor, based on especially designed experiments, are given. In all experiments, two of the three phases are given the same potential, i.e., no net torque is generated and the motor is at standstill. Input to the system is the reference values for the stator voltages given as duty cycles for the PWM power device. The system output is the measured stator currents. Three experiments are described giving respectively: (1) the stator resistance and inverter parameters; (2) the stator transient inductance; and (3) the referred rotor resistance and magnetizing inductance. The method developed in the two last experiments is independent of the inverter nonlinearity. New methods for system identification concerning saturation of the magnetic flux are given and a reference value for the flux level is derived. Experimental results are compared to factory measured values, and the difference may be explained by temperature variations and saturation effects.