Analytical methods for estimating equivalent thermal conductivity in impregnated electrical windings formed using Litz wire

Comparative study of thermal properties of electrical windings impregnated with alternative varnish materials

“…A new analytical method is proposed here to estimate the thermal conductivity of the impregnated windings formed with round conductors based on the double‐homogenisation approach [3, 13]. The proposed method homogenises the conductor and conductor insulation first as opposed to the existing approach, where the impregnation material and conductor insulation are dealt with first [5].…”

“…Table 3 lists the equivalent thermal conductivity of winding region and laminated stator core pack assumed in this analysis [3]. The equivalent thermal conductivity of the winding region is derived based on the material samples.…”

“…Also, varnish impregnation is more robust when considering transient thermal overload operation. However, windings potted using epoxy resins have significantly improved heat transfer capability [1, 3, 4].…”

Thermal modelling of high-frequency magnetic components for power electronics by Finite Element Analysis

“…As stated in the review from Pietrak et al in [33], some of the previous approaches can be used to get the effective (equivalent) thermal conductivity which is the magnitude of interest of the present work. And more particularly, they are perfectly suitable to homogenize electrical litz bundles for electrical machines [34]- [38] and inductors or transformers for power converters [39], [40]. The effective thermal conductivity, k w , calculated by these approaches will govern the heat equation,…”

“…It shows good accuracy, but it might be complex. The methodologies from Wrobel et al [38] and Kyaw et al [40] are based in the use of thermal networks. Both approaches require calibration with measurements in order to avoid the tolerances from the data provided by manufacturers or the lack of that information.…”