Jaroslaw Luszcz

Modeling of common mode currents induced by motor cable in converter fed AC motor drives

Investigation of conducted EMI generation in AC motor fed by pulse width modulated frequency converters requires to consider parasitic capacitances in converters, motor windings and feeding cables to be taken into account. Motor voltage transients and related common mode currents are significantly correlated with resonance effects occurring in load circuits. An analysis of frequency converter load impedance-frequency characteristics allows for identification and determination of frequency ranges in which the foremost contributions to EMI noise generation have the voltage ringing phenomena associated with the load parasitic capacitances. This paper presents a method to model an AC motor with a feeding cable in conducted EMI frequency range up to 30 MHz. Distributed parasitic capacitances of AC motor windings are modeled by a ladder circuit. The proposed circuit model allows for an analysis of the influence of motor feeding cable parameters on common mode currents generated in AC motor drive system, particularly in AC motor itself. The simulation results obtained based on the proposed ladder circuit model are verified by the experimental tests which have been carried out for an exemplary adjustable speed AC motor drive application.

Voltage harmonic distortion measurement issue in smart-grid distribution system

This paper presents the investigation results of voltage harmonic transfer accuracy problems through voltage transformers which are widely used in power quality monitoring systems in medium and high voltage grids. A simplified lumped parameters circuit model of the voltage transformer is presented and verified by simulation and experimental investigations. A number voltage transformers typically used in medium voltage grid has been tested in the conducted electromagnetic interference frequency range up to 30 MHz. The obtained results confirm that broadband voltage transfer function of the voltage transformer usually exhibits various irregularities which are primarily associated with voltage transformer winding parasitic capacitances.

AC Motor Windings Circuit Model for Common Mode EMI Currents Analysis

Investigation of common mode (CM) currents flowing in an AC motor as a result of a frequency converters output excessive voltage stresses, requires a model of the motor that take into account parasitic capacitances existing in the motor windings. The paper presents a circuit modelling method of the AC motor windings parasitic capacitances, which allows to take into account the change of the winding to ground capacitance for different frequency ranges in the conducted frequency range. The proposed circuit model and its parameter identification method make possible more accurate CM currents modelling in the AC motor windings fed by converter.

AC motor transients and EMI emission analysis in the ASD by parasitic resonance effects identification

Investigation of common mode (CM) electromagnetic interference (EMI) currents in an AC motor fed by the pulse width modulated (PWM) voltage converter requires a model of the motor that take into account parasitic capacitances existing in the motor windings. Presented CM transfer impedance analysis method shows that the motor voltage transient is strongly related to the resonance effects observed on the windings CM impedance. The wide frequency CM impedance characteristics analysis allows to identify and determine resonance effects which are the primary reasons for voltage ringing phenomena. The paper presents a circuit modelling method of the AC motor windings parasitic capacitances, which allows to take into account the change of the winding to ground capacitance for different frequency ranges in the conducted frequency range. The proposed circuit model and its parameter identification method make possible more accurate CM currents modelling in the AC motor windings fed by the converter.

Motor cable influence on the converter fed AC motor drive conducted EMI emission

Investigation of common mode (CM) electromagnetic interference (EMI) currents in an AC motor drive fed by the pulse width modulated (PWM) voltage converter requires that parasitic capacitances existing in the converter, motor windings and feeding cable have to be taken into account. The motor voltage transients and related EMI emission are strongly correlated with resonance effects detectable in load circuits. The frequency impedance characteristics analysis allows to identify and determine resonance frequency ranges which are the foremost contribution for voltage ringing phenomena. The paper presents a method of analysis of AC motor windings parasitic capacitances with the particular account of cable influence on the broad-spectrum overall performance. The proposed circuit model allows for analysis of cable parameters effect on the conducted EMI emission of the AC motor drive.

Motor cable effect on the converter fed AC motor common mode current

Analysis of conducted EMI in AC motor drives fed by pulse width modulated voltage converters requires to consider parasitic capacitances in converters, motor windings and feeding cables to be taken into account. Motor voltage transients and related common mode currents are significantly correlated with resonance effects occurring in load circuits. The levels of intensity of these phenomena depend noticeably on frequency dependant impedance — frequency characteristics of converter load, motor windings and feeding cable. An analysis of frequency converter load impedance characteristics allows for identification and determination of frequency ranges in which the foremost contributions to EMI noise generation have voltage ringing phenomena associated with the load parasitic capacitances. This paper presents a method to model an AC motor with a feeding cable in conducted EMI frequency range up to 30 Mhz. Distributed parasitic capacitances of AC motor windings are modelled as a ladder circuit. The proposed circuit model allows for an analysis of the influence of the motor feeding cable parameters on common mode currents generated in AC motor drive system, particularly in AC motor itself. The simulation results obtained based on the proposed ladder circuit model are verified by the experimental tests which were carried out for an exemplary adjustable speed AC motor drive application.

Evaluation of selected diagnostic variables for the purpose of assessing the ageing effects in high-power IGBTs

A method is presented and discussed whereby to evaluate two basic diagnostic variables that can be used in the assessment of the health of high-power IGBT packs. The proposed approach attempts to adapt a laboratory-grade method known from the literature for the use on board electric traction vehicles. The diagnostic variables in question are the junction-to-case thermal resistance and the collector-emitter saturation voltage. These variables can be used in the assessment of the depth of IGBT structure delamination and wire-bond lift-off. The proposed approach has been partially validated by experiment.

Low Frequency Conducted Emissions of Grid Connected Static Converters

Pulse-width modulated rectifiers are nowadays commonly used for AC to DC power conversion. PWM rectification technology is very effective and allows for bidirectional power flow with the possibility of power factor improvement and low-order harmonic emission limitation. Unfortunately, employed PWM boost topology results with generation of input current harmonic distortions in a frequency range tightly correlated to modulation frequency. PWM carrier frequency and its harmonic components in typical applications are usually located in frequency range from single kHz up to hundreds of kHz. Increase of harmonic emission in this particular frequency range can be disturbing for other sensitive systems, therefore can cause lack of electromagnetic compatibility. Interferences in low frequency range are increasingly frequent EMC issue because of extensive use of low power PWM rectifiers and significant increase of rated power of individual converters, which already reach several MW. Presented comparison of current harmonic emission spectra of PWM rectifiers with relation to classic diode rectifiers is focused on frequency range of 2 to 9 kHz, for which emission limitation rules are currently under development. New class of EMC problems arising in low frequency range in power system are underlined as a result of increased harmonic emission in frequency range of 2 to 9 kHz.

Broadband modeling of motor cable impact on common mode currents in VFD

Examination of conducted EMI generation and propagation in AC motor drives fed by frequency converter requires to consider parasitic capacitances in converters, motor windings and feeding cables to be taken into account. AC motor winding voltage transients and related common mode currents are significantly correlated with resonance effects occurring in converters load circuits. Intensity levels of these phenomena depend significantly on impedance - frequency characteristics of converters load, motor windings and feeding cable. An analysis of converters load impedance in frequency domain allows for identification and determination of frequency ranges in which the foremost contributions to EMI noise generation have voltage ringing phenomena associated with load parasitic capacitances. This paper presents a method to model an AC motor with a feeding cable in conducted EMI frequency range up to 30 Mhz. Distributed parasitic capacitances of AC motor windings are modeled using a ladder circuit. The proposed circuit model allows for an analysis of the influence of the motor feeding cable parameters on generated common mode current spectra in AC motor drive, particularly in AC motor itself. Obtained simulation results based on the proposed ladder circuit model are verified by the experimental investigations which were carried out for an exemplary AC motor drive.

High frequency harmonics emission of modern power electronic AC-DC converters

Modern AC/DC converters with bidirectional power flow employing PWM boost topology generate harmonic distortions of input current in relatively high frequency range tightly related to modulation carrier frequency. These frequencies and its multiples in typical applications are usually located in frequency range from single up to several of kHz. Increased harmonic emission in this frequency range can easily and harmfully influence sensitive control and measurement systems what occurs more often nowadays in applications where high power AC/DC PWM boost converted are used. This paper presents a comparison of current harmonic emission of PWM boost rectifiers with relation to classic diode rectifiers. New class of electromagnetic compatibility problems arising in power system are underlined as a result of increased harmonic distortions emission in frequency range up to 9 kHz.