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Comparative Study of Thermal Properties of Electrical Windings Impregnated with Alternative Varnish Materials

Lookup NU author(s): Dr Rafal Wrobel



This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).


The thermal design-analysis of devices with electrical windings impregnated using varnish materials is frequently challenging. This is due to difficulties in predicting theoretically the equivalent thermal properties for the composite materials, such as impregnated windings, in a reliable manner. The existing approach makes use of the impregnation ‘goodness’ factor, which allows for imperfections associated with the winding impregnation to be accounted for. This however, requires experimentally derived data from appropriate material samples or machine assemblies. Considering relatively large range of commercially available varnishes, such data is often limited and is not readily accessible. In this investigation, a set of three alternative varnish materials commonly used in impregnation of low voltage electrical windings has been evaluated. To provide better understanding of the material impregnating properties, data from multiple impregnations is also provided. The experimental findings have been supplemented with theoretical analysis on the impregnation ‘goodness’ and stator-winding contact thermal resistance for a selected winding construction. To highlight the importance of appropriate input thermal material data, a case study machine design is thermally analysed.

Publication metadata

Author(s): Liu H, Ayat S, Wrobel R, Zhang C

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: The 9th International Conference on Power Electronics, Machines and Drives (PEMD 2018)

Year of Conference: 2018

Pages: 1-6

Print publication date: 19/04/2018

Acceptance date: 14/02/2018

Publisher: IET