EPE Journal Volume 04-4 
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EPE Journal Volume 04-4 - Editorial
EPE Journal Volume 04-4 - Papers



 EPE Journal Volume 04-4 - Editorial 

See you in '95  [Details]
By B. Sneyers

The Editorial of the EPE Journal Volume 04 N°4, "See you in '95", written by Ir. Brigitte Sneyers, the Editor of EPE Association.


 EPE Journal Volume 04-4 - Papers 

Characterization of New Generation IGBT-modules  [Details]
By F. Blaabjerg; J. K. Pedersen; U. Jaeger

The development of IGBT devices is still moving ahead faster devices with lower losses. This paper will focus on charcterization of a third generation IGBT-module and a second generation IGBT-module with improved free-wheeling diodes where especially the power losses are compared in different test conditions. The characterzization is done on an advanced measurement system which is described. The diodes in the IGBT-modules are also investigated because it can be a limiting factor in many applications. Finally, short circuit tests are performed and a comparison of the two modules is done. The comparison shows the third-generation IGBT has the best short circuit capability and lowest on-state losses, while the second generation IGBT has the lowest switching losses.

Design of High-Frequency Mag Amp Output Regulators Using Metglas (R) Amorphous Alloy 2714A  [Details]
By J. S. Elias

Mag amp (magnetic amplifier) output regulators have recently become very popular as a means of regulating more than one output of a switching power supply. They offer extremely precise regulation of each independant output, and are efficient, simple and very reliable. Mag amps are particularly well suited for outputs with currents of 1 A to several tens of amps; however, they are also used at lower currents where tight regulation and efficiency are extremely important. The advant of cobalt-based amorphous alloy has made possible the design of mag amps that can operate at higher frequencies than previously possible in output regulation. Cores made from this alloy exhibit: (1) a high squareness ratio, giving rise to low saturated permeability; (2) low coercive force, indicating a small reset current and (3) low core loss, resulting in a smaller temperature rise. Although there are alternatives for post output regulation, mag almp regulation is the most efficient, reliable and low cost design.
This article describes the operation of modern mag amp regulators and guides the reader through the design of the saturable reactor and the control circuitry to achieve a 3.3 V, 20 A output. This mag amp is being developed to power the new generation of ultra-compact integrated circuits such as Intel's new Pentium microprocessor.

Commutation Types in Resonant Evolution Converters (II)  [Details]
By M. Hernando; M. Rico; V. García; J. Sebastian

In Part I of this paper, a classification of converters with resonant load was made, and these converters were devided into two families: Resonant Evolution Converters and Resonant Commutation Converters. A study of commutations for Resonant Evolution Converters was made for the voltage fed topologies. In part II, the commutat(ions for current fed topologies are studied. Also certain questions regarding energy are considered, and simulations and experimental results are shown.

Part I of this paper can be found in EPE Journal Volume 1994-3.

A Powerfull and Efficient Hysteresis PWM Controlled Inverter  [Details]
By I. Fatouh El-Sayed

A new control strategy related to hysteresis control method for inverters is presented. It permits to form the output wave easily and efficiently by means of PWM. This formation method is based on a new powerful modulation mode. The proposed inverter control scheme allows improvements on the AC drive performances while using simple dedicated hardware. The flexibility gained by the proposed method can achieve easily the self adaptation with minimum switching frequency, and consequently high inverter capability. The proposed scheme would be attractive for recent applications that requires non standard wave forms. In this paper, firstly, a comparison between the known bipolar and unipolar modulation modes is given. The drawbacks of these modulation modes are studied and a modified hysteresis controller is proposed. Then a new hysteresis control structure is presented and tested. It realizes an efficient and powerful modulation method that provides a so called freepolar PWM mode. This mode exhibits the advantages of the bipolar and unipolar modulation modes. The new control method solves the hard dependency of the controlled state on supply voltage and load parameters. Comparisons between different control structures for sinusoidal and non-sinusoidal operations are given. The investigation method considers all practical constraints for the power electronic devices and micro-electronic integrated circuits using PSpice.

Design Criteria for Transformers in High Voltage Output, High Frequency Power Converter Applications  [Details]
By M. A. Pérez García; C. J. Blanco Viejo; M. Rico Secades; J. Díaz González

When a dc high voltage needs to be obtained from low voltage inputs (main voltage), the necessary power converter needs a high value for its transformation ratio; consequently, a large number of turns is often necessary for secondary windings and some parasitics appear (large leakage inductance and large capacitance). Thus, it is usual to design a resonant converter to include both inductance and capacitance in the power topology. However, as the parasitics are used to obtain the resonance, their value (and their spreads) are critical. The present paper proposes several criteria in order to establish an adequate method for constructing the transformer, and a new topology for transformers and a model for parasitic capacitances are also presented taking into account high voltage and high frequency problems and limitations of materials.