Pieter Jacqmaer

ABSTRACT For determining the dynamic ON-resistance Rdyn,on of a power transistor, the voltage and current waveforms have to be measured during the switching operation. The novel heterostructure wide-bandgap (e.g., AlGaN/GaN) transistors inherently suffer from the current collapse phenomenon, causing the dynamic ON-resistance to be different from the static. Measuring voltage waveforms using an oscilloscope distorts the characteristics of an amplifier inside the oscilloscope when the range of the measurement channel is not set wide enough to measure both ON-state and OFF-state voltage levels, resulting in failure to accurately measure the voltage waveforms. A novel voltage clamp circuit improving the accuracy of the transistor's ON-state voltage measurement is presented. Unlike the traditional clamping circuit, the presented voltage clamp circuit does not introduce delay caused by RC time constants, keeping the voltage waveform clear, even during state transitions of the device under test. The performance of the presented circuit is illustrated by measurements on a 2-MHz inverted buck converter.

ABSTRACT This paper calculates the electric and magnetic fields and the Poynting vector around two infinitely long parallel cylindrical conductors, carrying a DC current. Also the charges on the surface of the wire are calculated, and their distribution is visualized. The wire is assumed to be perfectly electrically conducting. Furthermore, the Hall effect is ignored. In the literature [S.J. Orfanidis, Electromagnetic waves and antennas, 2008], the problem of determining the electric field is usually tackled using an equivalent model consisting of two line charge densities, producing the same electric field. In this work, the Laplace equation is rigorously solved. The authors found no work explaining the solution of the Laplace equation with boundary conditions for this problem and hence thought it was useful to dedicate a paper to this topic. The method of separation of variables is employed and a bipolar coordinate system is used. After solving the appropriate Sturm-Liouville problems, the scalar potential is obtained. Taking the gradient yields the electric field. Contribution to the Topical Issue "Numelec 2012", Edited by Adel Razek.

This document presents the work done for the Belgian railway operator Infrabel with respect to the modeling of grounding systems. Infrabel needed information on how to design the lightning protection systems of the recently deployed GSM-R installations. There exist many methods for simulating lightning strikes on grounding systems. One of these techniques, an electromagnetic method based on Moment Methods, is used to solve the problem. The theory behind the method is described and a novel technique is presented for simulating cylindrical cables without metal sheets. The method is applied to the grounding of the Infrabel GSM-R base station. The influence of the soil conductivity, the length of cables and grounding rods and the type of lightning strike on the effectiveness of the grounding system is researched.

A method for solving the full equations of Maxwell for circuits with discrete nonlinear, nonideal elements is presented. To this end, the method of moments is used in combination with a classical circuit simulator. Both operate in the frequency domain. A few methods to greatly accelerate the calculations are also presented. The methods are implemented and tested in Matlab.

A hybrid electric Kart is built as a didactical project for the students of the Master of Engineering: Energy of the K.U.Leuven. In order to cope with the growing number of students, a modular hybrid electric kart is conceived. The hybrid configuration allows to diversify between several tasks that have to be addressed by the students. The tasks include a control scheme for an induction motor, a control scheme and design of a power-factor-correction converter which enables power flow between the DC-link and a gasoline generator and finally the control scheme and design of a DC/DC converter allowing bidirectional power flow between a low voltage battery and the DC-link. All control schemes are supervised by a top level control scheme which maximises efficiency. The control schemes are programmed in Matlab/Simulink. A rapid-prototyping control board runs the model made in Matlab/Simulink. The control board interfaces between the different sensors and power electronics present on the kart.

For determining the dynamic on-resistance Rdyn,on of a power transistor, the voltage and current waveforms have to be measured during the switching operation. In measurements of voltage waveforms, using an oscilloscope, the characteristics of an amplifier inside the oscilloscope are distorted when the range of the measurement channel is not set wide enough to measure both on-state and off-state voltage, resulting in failure to accurately measure the voltage waveforms. A novel voltage clamp circuit improving the accuracy of the transistor on-state voltage measurement is presented. The measurement accuracy is improved by clamping the off-state voltage across the transistor to a lower voltage that is still greater than the on-state voltage. Unlike traditional clamping circuit, the presented voltage clamp circuit does not introduce delay caused by RC time constants keeping the voltage waveform clear even during state transitions of the evaluated semiconductor device for frequencies up to 1MHz.