采用氮化铝材料的水冷变压器的热管理方法

doi:10.19595/j.cnki.1000-6753.tces.231685

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Abstract Dry-type high-frequency transformers typically have compact structures and significant losses. The use of potting materials with low thermal conductivity can lead to heat accumulation within the large-capacity transformer, resulting in temperature rise becoming a limiting factor in increasing the power density of high-frequency transformers. Due to the significant advantages of toroidal cores and water-cooling heat dissipation method, this paper focuses on the thermal management issue of toroidal water-cooling transformers.
Because of the axisymmetric structure of the toroidal transformer, the thermal circuit of the transformer can be equivalently described using a two-dimensional model. In order to calculate the temperature rise, this paper establishes a lumped parameter two-dimensional equivalent thermal circuit model of the toroidal transformer based on the thermoelectric analogy theory, with the center and the four surfaces of the magnetic core as temperature nodes. Compared with existing models, the proposed model takes into account the thermal resistance of the central cylinder formed after sealing. The modeling of the thermal resistance between the side and bottom surfaces of the central cylinder is based on the analysis of heat flow path. This heat flow path is a curve, but solving the thermal resistance along the curve is difficult. This paper simplifies it by dividing the heat flow path into horizontal and vertical sections. The thermal resistances of these two sections are in series, so the thermal resistance of the cylinder is the sum of them. The accuracy of the simplification method is verified by finite element simulation.
With the established thermal circuit model, the phenomenon that the temperature decrease of the transformer tends to remain constant as the water flow rate increases is explained. The cause of this phenomenon is the relatively high thermal resistance between the heat source and the water-cooling plate, resulting in less heat reaching the water-cooling plate and limited cooling effect. Therefore, it is necessary to find an insulation material with strong thermal conductivity to meet the heat dissipation requirements of potting transformers.
Taking inspiration from the packaging materials of high-power semiconductor module, Aluminum Nitride material with both insulation and heat dissipation capabilities is suggested and applied in high-power transformers. Based on this high thermal conductivity insulation material, this paper proposes a new heat dissipation structure.
This structure provides a low thermal resistance channel between the heat source and the water-cooling plate, and allows further increase in capacity and power density of high-frequency transformers. In addition, due to the larger core loss in the inner circle of the toroidal core and the denser winding on the inner side of the core, the thermal density in the inner direction of the transformer is higher than that in the outer direction, and the proposed heat dissipation structure enhances the thermal conductivity in the inner direction, so it is highly suitable for the toroidal transformers.
Finite element simulation and experiments conducted on the 25 kHz/160 kV·A high-frequency transformer prototype prove that the temperature rise of the transformer using aluminum nitride heat dissipation structure is lower than that of the fully epoxy resin potted transformer, verifying the effectiveness of the proposed heat dissipation structure.

Key words： High-power high-frequency transformer toroidal water-cooling transformer equivalent thermal circuit model aluminum nitride material

Received: 12 October 2023

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TM433

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	Articles by authors
	Wang Kaiguo
	Gong Jinwu
	Shi Zishuai
	Tian Jie
	Pan Shangzhi
	Zha Xiaoming

Cite this article:

Wang Kaiguo,Gong Jinwu,Shi Zishuai等. Thermal Management Method for Toroidal Water-Cooling Transformer Using Aluminum Nitride Material[J]. Transactions of China Electrotechnical Society, 2024, 39(21): 6614-6625.

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https://dgjsxb.ces-transaction.com/EN/10.19595/j.cnki.1000-6753.tces.231685 OR https://dgjsxb.ces-transaction.com/EN/Y2024/V39/I21/6614

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