Estimation of parameters of induction machines based on instantaneous impedance
This paper proposes a method for parameter estimation of three-phase induction machines based on the concept of instantaneous impedance and using only stator voltages and currents acquired during a no-load startup transient. Basically, the method estimates the parameters using an optimization algorithm which aims to reduce the error between estimated and measured instantaneous impedance. The algorithm assumes that the stator resistance is known and that part of the parameters are estimated from the steady state condition. Stator flux, electromagnetic torque, and rotor speed, required to determine the parameters, are also estimated from measurements. Practical experiments involving two machines of different power (5.5 and 30 kW) were used to validate the proposed algorithm. These experiments showed that the mechanical and electrical parameters can be estimated with acceptable errors in the case of the 5.5-kW machine. In contrast, in the case of the 30-kW machine, the estimation of the rotor parameters is influenced by factors not considered in the model, especially the skin effect. In this case, the use of an algorithm based on deceleration tests combined with the method based on the instantaneous impedance improved the results. Finally, the estimated parameters are compared with those declared by the manufacturer and the agreement between them is discussed.