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EPE Journal Volume 03-4 - Papers
EPE Journal Volume 03-4 - Editorial
By B. Sneyers
The Editorial of the EPE Journal Volume 3 N°4, "To our Readers...", written by Ir. Brigitte Sneyers, the Editor of EPE Association.
EPE Journal Volume 03-4 - Papers
By D. O'Sullivan
In order to undestand the key differences between space and industrial power electronics, it is essential that those features that are unique to the space environment are clearly identified. In the first part of this paper those key drivers that effect the choice of design approach will be described and the remainder of the paper will illustrate how these drivers effect the choice of regulator topologiesand the overall approach to power system design.
The First part of this paper can be found in EPE Journal Volume 1993-2 and the second part in EPE Journal Volume 1993-3.
By P. Zwanziger
The economic and technical advantages power converters with IGBTs offer are the result of lower costs for gate drive circuitry, a favourable trend in price developments and the enhanced ruggedness of these semiconductor devices. Different applications can be implemented by simply adapting the gate drive circuit, though specific switching characteristics and parasitic stray inductances have to be taken into account, especially under fault conditions. The example of a safe operating area (SOA) from the view of application is calculated to illustrate this. Turn-off under short-circuit conditions in the critical time space of a gate drive circuit will become manageable by active clamping of the collector over-voltage. Parallel connections can be quatitatively described by dynamic and steady-state temperature-dependent asymmetries in the current distribution. An analysis of the electrothermal correlations between the elements creates a better calculation basis for investigating the sensitivity of parameters to different temperature coefficients of the IGBT and freewheeling diode. This is finally folowed by a presentation from the user's point of view of problems to be expected later with regard to increasing the switching capacity of IGBT modules.
Part I of this paper can be read in EPE Journal Volume 1993-3.
By J.-F. Kamp
In lighting applications the electronic ballast is a unit which provides ignition and power supply for fluorescent tubes. More and more frequently, it becomes a substitute for the classical system consisting of an inductive ballast and a starter. Several reasons explain this evolution: better power factor, high frequency power supply of the tube, low heating, etc. Some electronic units are connected to the mains, others are powered by a DC voltage source. The electronic ballast considered in this paper is used in an emergency lighting unit where the DC voltage is provided by a battery. It consists of an lc oscillator and two transistors acting as DC-AC convertersbetween the source and the oscillator. The fluorescent tube is connected to the oscillator via a transformer. This type of electronic ballast stands out because of its simplicity and robustness which explains why it is particularly well suited for emergency lighting.
The paper starts with a detailed theoretical analysis of the electronic circuit, based essentially on the principle of harmonic balance and resulting in a set of mathematical expressions for the most important quantities such as currents and voltages in the oscillator and tube as well as oscillation frequency. These expressions are general in the sense that they hold independently of the specific values of the DC voltage source and the power of the fluorescent tube.
Relying on these expressions we give then to the designer a logical approach for choosing the correct values of the circuit components in order to satisfy the requirements concerning lighting intensity, oscillation frequency and autonomy of the unit.
Finally, we also provide an experimental verification of the results for specific case of a unit described for a 8 watt fluorescent tube. This verification confirms the soundness of the approach followed in the theoretical analysis.
By E. Monmasson; J. C. Hapiot; M. Grandpierre
In recent years, the ever-increasing capabilities of microelectronic devices allowed the implementation of more and more sophisticated speed drives. Hence, the control structure performs a greater number and a wider range of functions.
The difference in the nature of these functions pushed the designer to investigate the architecture on the one hand, and the implementation on the other hand.
The present study is carried within the scope of this new trend. A control system fully implemented on FPGA and capable of controlling the currents in the machine is described. The definition of FPGAs is reviewed and the reasons for this choice are discussed; the advantages of this technology are discussed as well as the difficulties encountered at the development stage. Then, the experimental results are detailed.
By R. Gretsch; W. Gunselmann
Caused by the increasing use of DC power supplies based on rectifiers with capacitive smoothing, the harmonic voltage levels are continuously rising in public mains systems. Remedial measures are necessary as the compatibility level will be reached soon.
The "standard solution" for reducing the harmonic emission of these appliances by inserting an inductance into the circuit imposes some disadvantages.
A new dc power supply is presented which is able to compensate the harmonic currents of other devices by controlling itds main current according to the distortion of the mains voltage. Several control strategies as well as stability problems caused by the interaction of many of these power supplies and the mains system are discussed. Finally, the overall harmonic reduction is assessed under reasonable assumptions.