29 March 2019

Toothband and Clackband

A power transformer winding must comply with various requirements under test and guarantee electrical strength in all operating conditions. In addition, the winding must not overheat. A number of concepts are used to avoid the occurrence of overheating. Forming an axial intermediate cooling duct within the winding is a common design principle, especially in the case of wider disc windings. A simple technical solution to achieve this is to integrate Toothband or Clackband during the winding process.

Toothband consists of a single layer of insulating paper carrier tape (according to IEC 60641-3-2 type 4.1 A) on which blocks of hot-press-dried T IV are glued. The height of the winding conductor corresponds to the width of the tape, and the height of the blocks corresponds to the cooling channel. Toothband is also available in Nomex for use in high temperature class F transformers.

For many years Weidmann has been selling Clackband with trapezoidal blocks glued between two layers of paper. One advantage of this product is that it has high tensile strength, for example, 240 N at a band width of 15 mm. Added to this are the two layers of paper which make it almost impossible for the blocks to break out during the winding process. The base material of Clackband is identical to that of Toothband. However Clackband is more standardized and supplied in either blocks of 50 mm or 65 mm and tooth heights of 4 to 8 mm.

Thanks to highly automated equipment, Toothband and Clackband can be supplied in large quantities at short notice.