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 are often limited and are 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 are 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.

Conventionally, the small mean and variance of peak-to-peak cogging torque of permanent magnet (PM) machines considering manufacturing uncertainties can be achieved by a robust design or by reducing the uncertainties range. However, the consequent compromise of other design objectives or the increase in the manufacturing costs are frequently inevitable. In this paper, the combination sequence of the uncertainties is highlighted and implemented to achieve a stable performance even for a non-robust design without increasing the cost too much. A PM assembling approach is proposed to mitigate the influences of PM uncertainties on cogging torque by means of combining the uncertainties in a particular sequence, where the effects of uncertainties would counteract each other. Both the singular type of PM uncertainties and the combined ones are considered in the assembling approach. Furthermore, the proposed approach is verified by comparing the cogging torque performance with PM randomly assembled models, where several hundreds of models featuring different uncertainties are calculated through the finite element method. The proposed approach is discussed, particularly for the application of mass production and a small amount of prototypes. Two prototypes with different PM assembling sequences are fabricated and further verify the effectiveness of the proposed PM assembling approach.