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Towards a Standardised Approach of Deriving Thermal Parameters in the Design of Electrical Machines

Lookup NU author(s): Dr Rafal Wrobel

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

Abstract

This paper describes a methodology for experimentally deriving thermal parameters in the design of electrical machines, with a focus on, but not limited to, short-duty transient operation. Here, all key stator-winding thermal resistances and capacitances, which can be directly derived from thermal tests, are considered. The proposed approach is based on the transient thermal step-change response for a specimen /mottorete under test, where the heat transfer is well-defined and limited to a single path, e.g. a heat source (stator-winding body) to a heat sink (machine housing). Any imperfections like the heat flux leakage from the motorette body/test rig are considered and experimentally compensated for. A detailed description of the underpinning assumptions, test procedure, required instrumentation, and measured data post-processing is provided and supplemented with several examples from hardware tests. Applicability and limitations of the methodology are also discussed. The presented approach provides a novel standardised testing method, where the measured data can be simply shared across different electrical machine designs to bring a means for an accurate, time- and resource-effective design/assessment process. This expanded work elaborates more on the existing figures of merit, highlighting their deficiencies when thermally sizing electrical machines. Further to this, a more detailed discussion of the methodology, supplemented with new examples, is provided.

Publication metadata

Author(s): Wrobel R

Publication type: Article

Publication status: Published

Journal: IEEE Transactions on Industry Applications

Year: 2026

Volume: 62

Issue: 1

Pages: 975-984

Print publication date: 01/01/2026

Online publication date: 31/07/2025

Acceptance date: 18/07/2025

Date deposited: 04/08/2025

ISSN (print): 0093-9994

ISSN (electronic): 1939-9367

Publisher: IEEE

URL: https://doi.org/10.1109/TIA.2025.3594647

DOI: 10.1109/TIA.2025.3594647

ePrints DOI: 10.57711/7xyb-vv81

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