Thermal Modeling and Experimental Validation of Mid-Conductor Winding Cooling

Abstract

A direct cooling method for windings of electrical machines, mid-conductor winding cooling, is studied. Spaces between the wires are utilized as coolant channels, with a liquid being pumped through the winding along the length. These results in the elimination of thermal interface resistances, a high heat transfer area and heat transfer coefficient while maintaining the same cross-sectional area for the copper winding. A thermohydraulic model is made and validated to analyze the heat transfer rates and pressure drop. Validation measurements with a water-glycol mixture as coolant show that the modeled and measured pressure drop correspond within 0.07 bar and the modeled and measured winding temperature within 3 °C. When made relative to the temperature difference between winding and coolant, the deviation is equal to 12%. The validated model is used to analyze the performance when utilizing oil as coolant. For a winding temperature of 180 °C and a pressure drop of 1 bar, using the novel cooling method results in a maximal attainable current density equal to 39.4 A/mm² which is 41% higher than that attainable with spray end winding cooling.

Disclosure statement

The authors report there are no competing interests to declare.

Additional information

Funding

This work was supported in part by Flanders Make, the strategic research center for the manufacturing industry.

Notes on contributors

Ilya T’Jollyn

Ilya T’Jollyn received his M.Sc. degree in Electromechanical Engineering from Ghent University, Ghent, Belgium in 2014. In 2021, he successfully defended his doctoral dissertation with the title ‘Assessment of Nucleate Pool Boiling Heat Transfer and Critical Heat Flux for Power Electronics Cooling with a Low-GWP Refrigerant’. He is currently a postdoctoral researcher in the research group Sustainable Thermo-Fluid Energy Systems of the Department of Electromechanical, Systems and Metal Engineering at Ghent University. His research interests include heat transfer in electrical machines and systems, and he is currently working on two-phase power electronics cooling and innovative motor cooling techniques.

Jasper Nonneman

Jasper Nonneman received his B.Sc. degree in Electromechanical Engineering in 2014 and M.Sc. degree in Mechanical Energy Engineering 2016, both from the Faculty of Engineering and Architecture, Ghent University, Belgium. He is currently working as a Ph.D. researcher at the research group Sustainable Thermo-Fluid Energy Systems of the Department of Electromechanical, Systems and Metal Engineering at Ghent University, Belgium. His research interests are the cooling and thermal modeling of electric machines and power electronics.

Michel De Paepe

Michel De Paepe is a Professor of Thermodynamics and Heat Transfer at the Faculty of Engineering and Architecture of the Ghent University. He graduated with M.Sc. in Electromechanical Engineering at the Ghent University in 1995. In 1999 he obtained the Ph.D. in Electromechanical Engineering at the Ghent University, graduating on `Steam Injected Gas Turbines with water Recoverý. He is currently part of the Research Group Sustainable Thermo-Fluid Energy Systems at the Faculty of Engineering and Architecture of the Ghent University. Research in this group focuses on thermodynamics of new energy systems, performance of HVAC systems and energy in buildings and complex heat transfer phenomena in industrial applications, as in compact heat exchangers, combustion engines, electrical drives, refrigerant two-phase flow, and electronics cooling. He was supervisor/promotor of 29 PhDs defended at Ghent University. He is (co)author of 130 papers published in international peer reviewed journals and more than 430 conference papers.