Lagrangian dynamics model and practical implementation of an integrated transformer in multi-phase LLC resonant converter

Mostafa Noah; Kazuhiro Umetani; Jun Imaoka; Masayoshi Yamamoto

Lagrangian dynamics model and practical implementation of an integrated transformer in multi-phase LLC resonant converter

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Author(s): Mostafa Noah¹ ; Kazuhiro Umetani² ; Jun Imaoka³ ; Masayoshi Yamamoto¹
- Affiliations: 1: Electrical Engineering Department , Nagoya University , Furo-cho, Chikusa-ku, 464-8603 Aichi, Nagoya-shi , Japan ;
  2: Electrical Engineering Department , Okayama University , 3-1-1 Tsushimanaka-cho, Kita-ku, Okayama-shi , Japan ;
  3: Electrical Engineering Department , Kyushu University , 744 Motooka, Fukuoka-shi , Japan
Source: Volume 11, Issue 2, 20 February 2018, p. 339 – 347
DOI: 10.1049/iet-pel.2017.0485 , Print ISSN 1755-4535, Online ISSN 1755-4543

Received 07/07/2017, Accepted 28/09/2017, Revised 13/09/2017, Published 03/10/2017

In conventional arrangements of three-phase LLC converters, there are at least three magnetic components that occupy a considerable volume and mass of the power converter. Although, the three-phase LLC topology has many advantages over the single-phase one, circuit designers tend to select the single-phase topology because it has the minimal number of magnetic components. The purpose of this study is to reduce the number of the magnetic components of the three-phase topology, by integrating the three-discrete transformers into a single magnetic core, based on a theoretical framework. Lagrangian dynamics is applied to theoretically prove that it is possible to replace the three-discrete transformers by a single integrated transformer. The Lagrangian dynamics theory allowed us to derive a physically motivated model for the integrated transformer, in which each component of the integrated transformer has its own Lagrangian parameter. The Lagrangian model reveals that in a symmetrical design, there is no interphase coupling, and as a result the magnetic components can be downsized owing to the ac flux cancellation. Along with the theoretical discussion, the practical merits of implementing the integrated transformer is reported. Furthermore, the experimental tests are conducted utilizing a 500 W–390 V/12 V–200 kHz prototype.

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Lagrangian dynamics model and practical implementation of an integrated transformer in multi-phase LLC resonant converter

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