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Những tổn thất lạc trong các cuộn dây được tiếp tục phân loại như xoáy mất và lưu hành mất hiện tại. Các thiệt hại lạc khác xảy ra ở các bộ phận kết cấu thép. Luôn luôn có một số lượng các lĩnh vực rò rỉ trong tất cả các loại máy biến áp, máy biến áp điện lớn (giới hạn kích thước do hạn chế giao thông và không gian) | 5 Stray Losses in Structural Components The previous chapter covered the theory and fundamentals of eddy currents. It also covered in detail the estimation and reduction of stray losses in windings viz. eddy loss and circulating current loss. This chapter covers estimation of remaining stray losses which predominantly consist of stray losses in structural components. Various countermeasures required for the reduction of these stray losses and elimination of hot spots are discussed. The stray loss problem becomes increasingly important with growing transformer ratings. Ratings of generator transformers and interconnecting autotransformers are steadily increasing over last few decades. Stray losses of such large units can be appreciably high which can result in higher temperature rise affecting their life. This problem is particularly severe in the case of large autotransformers where actual impedance on equivalent two-winding rating is higher giving a very high value of stray leakage field. In the case of large generator transformers and furnace transformers stray loss due to high current carrying leads can become excessive causing hot spots. To become competitive in the global marketplace it is necessary to optimize material cost which usually leads to reduction in overall size of the transformer as a result of reduction in electrical and magnetic clearances. This has the effect of further increasing stray losses if effective shielding measures are not implemented. Size of a large power transformer is also limited by transportation constraints. Hence the magnitude of stray field incident on the structural parts increases much faster with growing rating of transformers. It is very important for a transformer designer to know and estimate accurately all the stray loss components because each kW of load loss may be capitalized by users from US 750 to US 2500. In large transformers a reduction of stray loss by even 3 to 5 kW can give a competitive advantage. 169 .
