Evaluation of Cooling Solutions and Performance for Electrical Machines
(2026) MVKM01 20261Department of Energy Sciences
- Abstract
- Effective cooling is critical for high-performance electric vehicle traction motors, where high
temperatures can reduce efficiency and limit power capability. While oil spray cooling pro-
vides effective heat removal from the end-winding region, its system complexity, cost, and
integration requirements motivate the development of alternative cooling solutions that re-
tain water as the working fluid. This thesis investigates a novel end-winding cooling concept
designed to improve heat extraction from the end-windings while maintaining the simplicity
of conventional water-jacket cooling systems.
The proposed concept, the High Thermal Conductivity Network (HTCN), is in essence a
network of bent flat copper heat pipes embedded in a... (More) - Effective cooling is critical for high-performance electric vehicle traction motors, where high
temperatures can reduce efficiency and limit power capability. While oil spray cooling pro-
vides effective heat removal from the end-winding region, its system complexity, cost, and
integration requirements motivate the development of alternative cooling solutions that re-
tain water as the working fluid. This thesis investigates a novel end-winding cooling concept
designed to improve heat extraction from the end-windings while maintaining the simplicity
of conventional water-jacket cooling systems.
The proposed concept, the High Thermal Conductivity Network (HTCN), is in essence a
network of bent flat copper heat pipes embedded in a thermally conductive epoxy potting
compound. The network acts as a high-conductivity thermal shortcut, conducting heat from
the end-windings to the water jacket far more effectively than potting compound alone
A baseline thermal model of the 2012 Nissan Leaf traction motor was developed in ANSYS
Motor-CAD and validated against published Lumped Parameter Thermal Network (LPTN)
results and experimental measurements. The validated model was used to investigate the
influence of thermal conductivity in the end-winding region on overall motor thermal perfor-
mance.
To evaluate the performance of the HTCN, six different geometries were manufactured and
experimentally tested using an end-winding motorette. Selected configurations were also
investigated through three-dimensional heat transfer simulations in COMSOL Multiphysics.
Both simulations and experiments showed that increasing the number of HTCN layers re-
duced the average end-winding temperature and reduces temperature variations in the end-
windings, with the largest reduction occurring when increasing from one to two layers. The
four-layer configuration achieved the lowest temperature, reducing the average end-winding
temperature by 3.8°C (7.7 %) compared with the single-layer design. Experimentally, the
HTCN achieved an effective thermal conductivity of 1 748 ±11 W/(mK), reducing the aver-
agewindinginterfacetemperatureby36.2°C(44%)comparedwithanair-filledconfiguration
and by 21.6°C (32 %) compared with epoxy potting alone. Larger bend intervals produced
a more uniform temperature distribution. Insulation resistance measurements confirmed ef-
fective electrical isolation between the heat pipes and windings under DC conditions. (Less) - Popular Abstract (Swedish)
- Kan framtidens elbilsmotorer kylas lika effektivt som dagens avancerade oljesystem, men med enklare och billigare vattenkylning? Det var frågan bakom mitt examensarbete vid Lunds universitet som undersökte en ny metod för att hålla temperaturen nere i elektriska drivmotorer.
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/student-papers/record/9250074
- author
- Hvid, Mikkel LU
- supervisor
- organization
- course
- MVKM01 20261
- year
- 2026
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Automotive Traction Motors, Water Cooling, End-Windings, Heat Pipes, HTCN, LPTN, FEA
- report number
- ISRN LUTMDN/TMHP-26/5714-SE
- ISSN
- 0282-1990
- language
- English
- id
- 9250074
- date added to LUP
- 2026-09-28 13:55:43
- date last changed
- 2026-09-28 13:55:43
@misc{9250074,
abstract = {{Effective cooling is critical for high-performance electric vehicle traction motors, where high
temperatures can reduce efficiency and limit power capability. While oil spray cooling pro-
vides effective heat removal from the end-winding region, its system complexity, cost, and
integration requirements motivate the development of alternative cooling solutions that re-
tain water as the working fluid. This thesis investigates a novel end-winding cooling concept
designed to improve heat extraction from the end-windings while maintaining the simplicity
of conventional water-jacket cooling systems.
The proposed concept, the High Thermal Conductivity Network (HTCN), is in essence a
network of bent flat copper heat pipes embedded in a thermally conductive epoxy potting
compound. The network acts as a high-conductivity thermal shortcut, conducting heat from
the end-windings to the water jacket far more effectively than potting compound alone
A baseline thermal model of the 2012 Nissan Leaf traction motor was developed in ANSYS
Motor-CAD and validated against published Lumped Parameter Thermal Network (LPTN)
results and experimental measurements. The validated model was used to investigate the
influence of thermal conductivity in the end-winding region on overall motor thermal perfor-
mance.
To evaluate the performance of the HTCN, six different geometries were manufactured and
experimentally tested using an end-winding motorette. Selected configurations were also
investigated through three-dimensional heat transfer simulations in COMSOL Multiphysics.
Both simulations and experiments showed that increasing the number of HTCN layers re-
duced the average end-winding temperature and reduces temperature variations in the end-
windings, with the largest reduction occurring when increasing from one to two layers. The
four-layer configuration achieved the lowest temperature, reducing the average end-winding
temperature by 3.8°C (7.7 %) compared with the single-layer design. Experimentally, the
HTCN achieved an effective thermal conductivity of 1 748 ±11 W/(mK), reducing the aver-
agewindinginterfacetemperatureby36.2°C(44%)comparedwithanair-filledconfiguration
and by 21.6°C (32 %) compared with epoxy potting alone. Larger bend intervals produced
a more uniform temperature distribution. Insulation resistance measurements confirmed ef-
fective electrical isolation between the heat pipes and windings under DC conditions.}},
author = {{Hvid, Mikkel}},
issn = {{0282-1990}},
language = {{eng}},
note = {{Student Paper}},
title = {{Evaluation of Cooling Solutions and Performance for Electrical Machines}},
year = {{2026}},
}