Inductance identification of an induction machine taking load-dependent saturation into account

Abstract

Abstract-The paper proposes an identification method for the inductances of induction machines, based on signal injection. Due to magnetic saturation, a saturation-induced saliency appears in the induction motor, and the total leakage inductance estimate depends on the angle of the excitation signal. The proposed identification method is based on a small-signal model that includes the saturation-induced saliency. Because of the saturation, the load also affects the estimate, and measurements are needed in different operating points. Using the identified total leakage inductance, an estimate of the stator inductance can be obtained. The identification method is applied to computer simulations and laboratory experiments of a 2.2-kW induction motor.

Stator Inductance Identification Based on Low-Speed Tests for Three-Level NPC Inverter-Fed Induction Motor Drives

“…However, using an identification method based on the aforementioned rotational tests means the identified stator inductance has low accuracy when the load is connected. The approaches by Zamora and Ranta et al [15,16] propose an on-line identification method for the stator inductance based on estimating the stator flux from the back-emf of the IM. However, this identification approach results in poor accuracy in low-speed conditions.…”

Online Identification of Parameters Defining the Saturation Characteristics of Induction Machines

“…4. As explained in [23], the maximum value of (29) corresponds to the best estimate of the leakage inductance. As the load torque increases, the leakage inductance decreases, and the leakage inductance identification has to be performed separately for every load level.…”

“…The identification is based on a simplified small-signal model presented in [22], and the principle of the identification method is the same as in [23], but here, a current signal is injected instead of a voltage signal. At higher frequencies, the relation between the stator voltage deviations and the stator current deviations can be modelled using a small-signal impedance matrix according to…”

“…The impedance matrix could also be obtained by using rotating current signal injection and analysing the clockwise and counter-clockwise components [25], [26]. Under the assumption that only the rotor leakage inductance saturation affects the small-signal characteristics at high frequencies, the leakage inductance seen in the rotor flux reference frame is [23] …”

Rotor parameter identification of saturated induction machines

“…The identification is based on an induction machine model, where the effects of magnetic saturation, skin effect, and eddy currents in the rotor core are taken into account. The total leakage inductance and the total resistance are identified using high-frequency signal injection [10], and the parameters of the model are fitted to the impedances obtained at several injection frequencies. Experimental results of a 45-kW induction machine are presented.…”