Electromagnetic interference (EMI) couplings between motor drive system and resolver circuit induce considerable EMI noise in resolver, which has a serious impact on the excitation and feedback signals of resolver. In order to suppress the EMI noise effectively, it is necessary to study the coupling mechanism between the motor drive system and the resolver circuit. In this article, an EMI estimation model of resolver is proposed. An electric vehicle motor drive system is used for analysis. Coupling effects between permanent-magnet synchronous machine and variable reluctance resolver are investigated and modeled. Impedance measurement and numerical simulation are used to extract model parameters. Based on the estimation model, the conversion of common-mode (CM) noise to differential-mode (DM) noise in resolver circuit is analyzed. The estimation model is validated by comparing simulated results and measured results. Then, a CM choke is designed in the resolver circuit to suppress the coupled EMI noise. This modeling method is applicable for analyzing the EMI noise coupling between motor drive system and other low-voltage sensitive circuits.

Electromagnetic interference (EMI) couplings between a motor drive and an adjacent communication network induce a considerable common-mode (CM) current in a communication cable, which has a serious impact on the performance of the communication network. In order to estimate the CM current, it is necessary to study the coupling mechanism between the motor drive and the communication network. In this paper, a commercial motor drive system with an RS485 communication circuit is used for analysis. The conducted and near-field coupling paths are analyzed and modeled. By integrating the models of coupling paths with the EMI models of the motor drive and the dc/dc converter, an estimation model of the CM current coupled to the communication cable is built. Furthermore, online measurement methods and numerical simulation are presented to extract the impedance parameters of the conducted and near-field coupling paths. The estimation model is validated by comparing the simulated currents with the measured currents in the two configurations. This model is applicable for estimating the CM current coupled to the communication cable in various configurations.

Flyback converters are widely used for implementation of low-power and multiple-output isolated power supplies. In flyback converter, the power semiconductor devices in the primary and secondary circuits are electromagnetic interference sources, which will induce common-mode noise (CMN). Transformer shielding foil is usually employed for suppressing the CMN in flyback converters. However, transformer shielding foil with inappropriate structure helps little for CMN reduction. In fact, the shielding effectiveness of flyback transformer is affected by the noise sources and the shielding foil structure parameters (length, width, and position). In order to improve the shielding effectiveness, this paper proposes a method to determine the shielding foil structure of the flyback transformer. This is realized through analysis and modeling of the CMN cancellation behavior of the flyback transformer. The method is validated by a comparison of CMN measurement results.

In power electronic devices, high-speed switching often causes serious electromagnetic interference (EMI) problems. For compliance with electromagnetic compatibility standards, EMI filters are widely used. This article develops an efficient modeling and optimization method of EMI filter by employing artificial neural network (ANN). A partly connected ANN, which is accurate and time saving in training procedure, is proposed to model an EMI filter. Moreover, genetic algorithm and the EMI filter model based on the partly connected ANN are applied to optimizing the EMI filter. Through comparing simulated and measured results of insertion loss of EMI filter, the proposed modeling and optimization method is validated. Compared to equivalent circuit model and electromagnetic model, the proposed method can establish a more accurate EMI filter model and can optimize the design of the EMI filter more efficiently.

In variable speed drive (VSD) system, pulse width modulation (PWM) technology often causes serious common-mode (CM) interference. In order to suppress the CM interference efficiently, it is necessary to analyze and forecast the CM interference theoretically. As an important element of CM interference propagation path, the CM impedance of induction motor needs to be modeled. In this paper, a novel modeling method of the CM impedance from 9 kHz to 30 MHz is proposed. Online measurement is performed to get the spectra of the CM voltage and the CM current. And an improved measurement method of CM voltage is developed. This method uses a high-pass filter to measure the high-frequency components of CM voltage. Based on measured results, the CM impedance in working state is extracted. Then, based on physical structure of induction motor, a high-frequency model is established to fit the extracted CM impedance. Nonlinear programming and Monte Carlo algorithm are used to calculate the model parameters. Through comparing measured and calculated results of the CM current on motor side, the CM impedance model is validated.

Shielding techniques are widely applied in suppression of common-mode noise (CMN) in flyback converters. Winding shielding is an attractive technique in a flyback transformer to suppress CMN from the converter because it is easy to manufacture without adding extra size and volume. But how to calculate the number of flyback transformer winding turns for suppressing CMN is still unknown. This letter proposes a quantitative method to determine the number of the shielding winding turns. It presents the CMN propagation paths when winding is used as the shielding layer in the flyback transformer and calculates the coefficient to find out the number of turns. The method is validated through comparison of CMN measurement results.