Induction machine behavioral modeling for prediction of EMI propagation

Abstract

Abstract. This paper presents the results of wideband behavioral modeling of an induction machine (IM). The proposed solution enables modeling the IM differential-and common-mode impedance for a frequency range from 1 kHz to 10 MHz. Methods of parameter extraction are derived from the measured IM impedances. The developed models of 1.5 kW and 7.5 kW induction machines are designed using the Saber Sketch scheme editor and simulated in the SABER simulator. Modeling validation is based on prediction of electromagnetic interference (EMI) emissions of common-mode and differential-mode current spectra of experimental inverter-fed IM drives. Most IM models dedicated for EMC analysis have been developed from the phase-belt winding model considered by Zhong et al. in [11]. This model includes winding leakage inductances, ground capacitive couplings, and the capacitances between coils. Further enhancement in [12] includes stator and rotor resistances, and resistances for eddy currents circuit representation. However, modeling results from [11,12] allow to reflect only the basic shape of the common-and differential-mode IM impedance frequency characteristics. Due to differences in values of winding inductance for common-and differential-mode operation for frequencies below 100kHz , the model has to be parameterized every time, depending on the type of analysis. An exemplary solution of this problem is shown in [13,14], where the additional mutual inductances between machine windings were considered. Despite the fact that the models' accuracy is reported high for frequencies up to 100 MHz, their topology is complex and the procedures of parameter extraction may be problematic.An interesting modeling approach has been presented in the series of papers [15][16][17][18], where a high-frequency equivalent circuit of the real coil has been used to develop a wideband model of induction machine windings. The topology of this model is less complicated than that of the model presented in [14], however, additional mutual inductances between machine windings for different phases are included. The extraction procedure of model parameters may be difficult in case of some parameters, e.g. the series model resistances. Moreover, additional measurements of machine stator windings are needed to extract the values of mutual inductances. Model accuracy is reported for frequencies up to 10 MHz.Another approach is proposed in [7], where the machine impedance is modeled using the equivalent circuit including the skin effect [19]. The model accuracy is satisfactory, but the resonance frequency f r5 , which is present in the differential-mode impedance characteristics (Fig. 3), has not been reported. The model parameters are also difficult to evaluate, because resolution algorithms of nonlinear systems have to be used.

Modeling of a Quasi-Resonant DC Link Inverter Dedicated to Common-Mode Voltage and Ground Current Reduction

“…Moreover, during the measurement, the input terminals of stator windings should be connected. Capacitive couplings distinctly dominate obtained frequency characteristic Z Cm (ω) with a small impact of inductive components in frequency bands "b" and "d" (Figure 7b) [15,27]. The typical value of capacitance C SR is small -about 10 pF to 100 pF, hence current i PE circulating through the ground wire is mainly determined by impedance Z SF [28].…”

On Medium Frequency Differential Mode Resonance Effects in Electric Machines

“…In the nineties, with the transition from thyristor based converters to voltage source converters (VSCs), with "fast switching" power electronic devices based on Silicon technology, new failure types, such as premature turn insulation, bearing failures, but also EMI-problems appeared in drive applications [1]- [5]. For actual converter types and switching frequencies, the underlying phenomena are for the most part understood and technical solutions exist [3], [6]- [11].…”