EPE Association: EPE 1985 - 02 - Lecture Session 1.02: PASSIVE COMPONENTS

EPE 1985 - 02 - Lecture Session 1.02: PASSIVE COMPONENTS
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   A SIMPLIFIED HIGH-FREQUENCY NETWORK REPRESENTATION OF POWER PULSE TRANSFORMERS FOR SWITCHED MODE DC-DC CONVERTERS AND DC-AC INVERTERS
By L. Bonte; J. Van Campenhout [View]
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Abstract: High frequency switching power converters are widely considerd interesting low-cost alternatives to their linear or SCR controlled counterparts because of their higher efficiency, smaller volume and weight. To a large extent, the cost of such switching power converters is determined by the size of the filter components and the isolation wide band power transformer(s). Converter cost can be reduced by using high switching frequencies, which lower the overall dimensions of the filter and the transformers. The advent of low-cost power MOS transistors allows switching frequencies up to 200 kHz. However, increasing the switching frequency introduces high constraints on the design of the power wide band isolation transformers. For example, the leakage inductance can cause severe voltage spikes during the turn-off transition of the transistors. At high switching speeds, leakage inductances behave as series impedances, and thus limit peak power transfer (Bonte, Baart 1983b). The combination of the transformer leakage inductances and winding capacitances results in high frequency (3-30 MHz) resonating modes. The energy accumulated in such modes increases with the switching frequency and rise time, and cannot be recuperated efficiently in most cases. Most of the published guidelines for high frequency power transformer design advocate the use of ferrite pot cores (Snelling, 1969). Pot core solutions are suggested because of their low achievable stray vs. magnatization inductances and low resistive losses. In this note, however, we show that better results can be obtained using toroidal ferrite core pulse transformers, both as to volume per unit power as well as to high frequency behavior. Furthermore, we present a simple, yet robust high frequency model for the pulse transformer which is far easier to use than the more complicated models in (O'Meara, 1961; Müller and Buckow, 1984). We first analyse published guidelines for the design of pulse transformers. Next we propose our own design, which outperforms the published data on several counts. Finally, we present a simple and robust high frequency network model for our transformer design.

   DEVELOPMENT OF COMMUTATION AND FILTER CAPACITORS FOR POWER ELECTRONICS
By M. Bramoulle [View]
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Abstract: Since the start of Power Electronics, capacitors volume reduction has always been considered as a permanent target. This performance is reached through 3 lines of development:
- new conceptions for the architecture of the electronic circuits,
- emergence of new components (GTO thyristors),
- actions on the technical design of the capacitors.
This paper shows the ways and means employed to develop these actions:
- reduction of the dielectric losses,
- increase of the working voltage stresses,
- increase of the specific energy,
while preserving the necessary level of reliability of these capacitors.
The evolution of the impregnated commutation capacitors is based on an improvement of the dielectric system, inducing to a very large reduction of the dielectric losses. In the range of the unimpregnated capacitors, the use of metallized film, with a reinforced side, without crenels for commutation, and with crenels for filter applications, gives a better control of the self-healing phenomena and allows to increase the working stresses. Unfortunately, the performances of the basic products, like the polypropylène film, remain constant and the working conditions draw more and more near the unchanged limits of the films. Therefore, it is important to know precisely the real working conditions of these capacitors.

EPE 1985 - 02 - Lecture Session 1.02: PASSIVE COMPONENTS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1985 - Conference > EPE 1985 - 02 - Lecture Session 1.02: PASSIVE COMPONENTS
	[return to parent folder]

	A SIMPLIFIED HIGH-FREQUENCY NETWORK REPRESENTATION OF POWER PULSE TRANSFORMERS FOR SWITCHED MODE DC-DC CONVERTERS AND DC-AC INVERTERS By L. Bonte; J. Van Campenhout	[View] [Download]
Abstract: High frequency switching power converters are widely considerd interesting low-cost alternatives to their linear or SCR controlled counterparts because of their higher efficiency, smaller volume and weight. To a large extent, the cost of such switching power converters is determined by the size of the filter components and the isolation wide band power transformer(s). Converter cost can be reduced by using high switching frequencies, which lower the overall dimensions of the filter and the transformers. The advent of low-cost power MOS transistors allows switching frequencies up to 200 kHz. However, increasing the switching frequency introduces high constraints on the design of the power wide band isolation transformers. For example, the leakage inductance can cause severe voltage spikes during the turn-off transition of the transistors. At high switching speeds, leakage inductances behave as series impedances, and thus limit peak power transfer (Bonte, Baart 1983b). The combination of the transformer leakage inductances and winding capacitances results in high frequency (3-30 MHz) resonating modes. The energy accumulated in such modes increases with the switching frequency and rise time, and cannot be recuperated efficiently in most cases. Most of the published guidelines for high frequency power transformer design advocate the use of ferrite pot cores (Snelling, 1969). Pot core solutions are suggested because of their low achievable stray vs. magnatization inductances and low resistive losses. In this note, however, we show that better results can be obtained using toroidal ferrite core pulse transformers, both as to volume per unit power as well as to high frequency behavior. Furthermore, we present a simple, yet robust high frequency model for the pulse transformer which is far easier to use than the more complicated models in (O'Meara, 1961; Müller and Buckow, 1984). We first analyse published guidelines for the design of pulse transformers. Next we propose our own design, which outperforms the published data on several counts. Finally, we present a simple and robust high frequency network model for our transformer design.

	DEVELOPMENT OF COMMUTATION AND FILTER CAPACITORS FOR POWER ELECTRONICS By M. Bramoulle	[View] [Download]
Abstract: Since the start of Power Electronics, capacitors volume reduction has always been considered as a permanent target. This performance is reached through 3 lines of development: - new conceptions for the architecture of the electronic circuits, - emergence of new components (GTO thyristors), - actions on the technical design of the capacitors. This paper shows the ways and means employed to develop these actions: - reduction of the dielectric losses, - increase of the working voltage stresses, - increase of the specific energy, while preserving the necessary level of reliability of these capacitors. The evolution of the impregnated commutation capacitors is based on an improvement of the dielectric system, inducing to a very large reduction of the dielectric losses. In the range of the unimpregnated capacitors, the use of metallized film, with a reinforced side, without crenels for commutation, and with crenels for filter applications, gives a better control of the self-healing phenomena and allows to increase the working stresses. Unfortunately, the performances of the basic products, like the polypropylène film, remain constant and the working conditions draw more and more near the unchanged limits of the films. Therefore, it is important to know precisely the real working conditions of these capacitors.