Off-line identification of the electrical parameters of an industrial servo drive system

This paper presents a step-by-step method for identifying the electrical parameters of an industrial servomotor drive system at standstill. The servomotor drive system consists of a voltage source inverter and an induction motor. The inverter nonlinearity caused by the turn-on/off time dependency of the current level in the switching transistors is described. The fact that no phase voltage detection for the identification scheme is available leads to a nonlinear mathematical model of the induction servomotor drive system at standstill. This model also includes the saturation effect. With this process model, a three step method is deduced to obtain the stator and rotor resistance, the leakage inductance and the mutual inductance as a function of the magnetizing current. Practical results which are obtained with an industrial induction servomotor drive system are also presented.