Jacques Ecrabey

Prediction and measurement of The magnetic near field of a static converter

Increases of switching levels and frequency make the compliance with radiated EMC standards more and more difficult. A modeling method based on the partial equivalent element circuit (PEEC) formulations, permitting to know the field emitted by the layout of complex power electronic structures, is presented in this paper. The near magnetic field of a buck chopper has been measured and calculated. The comparison of the simulated results with measurements shows the effectiveness of the modeling methods and of the near field acquisition bench.

A New Carrier-Based PWM for the Reduction of Common Mode Currents Applied to Neutral-Point-Clamped Inverters

Inverters used in adjustable speed drives create common mode voltages with high dv/dt transitions resulting in high frequency common mode currents which flow to the ground through stray capacitances. These common mode currents are known to damage the bearings of electric machines and cause malfunctions in other surrounding electronic devices, and therefore need to be confined by using bulky and expensive electromagnetic compatibility (EMC) filters. The presented work focuses on the three levels neutral-point-clamped (NPC) inverter and proposes a new pulse width modulation (PWM) strategy for the reduction of common mode currents by lowering the number of step variations of the common mode voltage. Unlike previous strategies, this carrier-based PWM pays attention to the real phenomena involved in the generation of common mode currents so as to efficiently reduce them by avoiding dead time effects. The new strategy has been implemented in a 20 kVA prototype and the experimental results presented in this paper confirm its best EMC behavior compared with classical PWM.

Layout techniques for reduction of common mode current in static converters

The radiation is, for the most part, generated by common-mode currents. This paper shows that action on layout can reduce common-mode currents effectively. Cost-effective, the common-mode current control enables the radiation level knowledge at the conception of a device. This is an important gain of time. Four boost structures are studied in order to validate first, experimentally and second by modelling, reduction common-mode current layouts, supposed effective. The simulated models are based on the partial equivalent element circuit (PEEC) method. We show also the impact of these layout techniques on radiated perturbations

Modelling and analysis of the magnetic field radiated by a switching mode power supply

In this paper, we have analyzed the behaviour of a switched mode power supply (flyback) in radiated near-field. We have modelled it by equivalent diagrams representing electric operations, including the parasitic elements. First, we have tried to link the amplitude of the spectra of the radiated magnetic field with the electrical quantities (current and voltage) during the different working phases of the converter. Then, under some assumptions, we have proposed a model of the transformer with parasitic elements, which is valid up to 6 MHz. Finally, this model is used to model the complete structure. The parameters of the model are extracted from measurements and/or technical data of the components (semi-conductors). So, we can determine the dominant resonance frequencies of the structure which are significant in radiated mode.

Modelling and analysis of the magnetic field radiated by a three phased inverter

In this paper, we analyzed the behavior of a three phased inverter used in speed drives in radiated mode and we modeled it by equivalent diagrams representing electric operation and including parasitic elements. First, we tried to link the amplitude spectra of the radiated magnetic field and the electrical time measurements (currents). Then, under some assumptions, we proposed a modelling of the main differential mode loop with parasitic elements. The model parameters are extracted from measurements and/or technical data of the components (semi-conductors). So, we can determine the dominant resonance frequencies of the structure which are significant in radiated mode.

Correlation between the near magnetic field radiated by an EMI filter and its electric working

In this paper, the behavior in radiated mode of an EMI filter used in speed drives is analyzed. It was identified as one of the main sources of magnetic near field radiation. On one hand, the EMI filter is located upstream from the speed drive and is the victim of the other radiation sources of the speed drive. On the other hand, these sources excite its parasitic elements and create new resonance frequencies. By analyzing input impedance and transfer function and magnetic field measurements, we tried to link the resonance frequencies of the amplitude spectra of the radiated magnetic field and the one of the electric characteristics.

Far field extrapolation from near field interactions and shielding influence investigations based on a FE-PEEC coupling method

Considering standards, the main source of far field emitted by power electronic structures is the common mode current generated by the floating potentials tracks. Moreover, due to the frequency and power increases, the compliance to EMC becomes more and more difficult. In consequence, it is necessary to investigate practical solutions to reduce the emitted field. A useful solution is the shielding of wounded components which are near field influent sources. But this solution may be not efficient for far field reduction and investigations concerning component placement can be a better and cheaper solution. A FE-PEEC hybrid method was developed and can be used to investigate near field interactions and shielding influence. The method is applied to a structure combining a common mode filter with the floating potentials of an inverter. Using the hybrid method, the near field interactions and the influence of the common mode inductance shielding are analyzed on the floating potentials which are the sensitive part of the structure.

Reduction of Common Mode Currents Generated by Three-Level Inverters with Consideration of Motor Overvoltages

In adjustable speed drive applications, the switching of the inverter semiconductors generates common mode currents as well as harmful overvoltages on the motor terminals when long cables are used. Consequently, bulky and expensive input and output filters must be used. This work aims at reducing these disturbances from their origin by using a three-level neutral-point-clamped (NPC) inverter controlled with a new pulse-width-modulation (PWM) strategy. Whereas previous common mode noise-reducing strategies usually generate higher overvoltages than conventional ones, the proposed PWM is able to manage both problems thanks to its internal degrees of freedom.

Implantation par porteuses d'une stratégie MLI réduisant les courants de mode commun générés par un onduleur NPC

This paper presents a new pulse-width-modulation strategy for the reduction of common-mode currents in adustable-speed-drive applications using a three-level neutral pointclamped inverter. It is implemented through a saw-tooth carrier-based modulator which makes it possible to control the degrees of freedom provided by the strategy.