Optimization of the efficiency of switched-mode power transformers

Pao Yue-kong Library Electronic Theses Database

Optimization of the efficiency of switched-mode power transformers


Author: Lai, Chi-wing
Title: Optimization of the efficiency of switched-mode power transformers
Year: 1999
Subject: Electric transformers
Switching circuits
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Applied Physics
Pages: iv, 100 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1483525
URI: http://theses.lib.polyu.edu.hk/handle/200/1017
Abstract: Switched-mode power supplies are widely used nowadays. Nearly all power supplies are working in switched-mode because of its higher efficiency and smaller size. In this project, the efficiency optimization of the switched-mode power transformers (SMPT) is investigated, consideration taking into the temperature rise limit, the safety requirement and the size of the transformers. The dissertation starts with a study and delineation of the origin of the core losses (hysteresis loss and eddy-current loss) and the conductor losses (a.c. power loss and d.c. power loss). The core losses of some ETD (Efficient Transformer Design) type cores (5 different sizes and 2 different materials) are measured within a temperature-controlling chamber at different operating frequencies and magnetic flux densities. The actual core losses are then compared with the calculated values, in which the calculations are based on the power loss formula provided by the cores' manufacturer. The conductor losses of the enamelled copper wires with different wire gauge are measured at different operating frequencies under constant ambient temperature. The results obtained are then compared with the predicted values. Finally, the procedures for core selection and winding design are given. The core selection methods based on the cores' nomograms and the area product factor are introduced. The essential background information behind the design rules for high-frequency transformer winding is discussed first and then a practical winding design procedure is proposed.

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