Direct air cooled hollow windings : Performance enhancement of electrically excited machines
Estenlund, Samuel LU
(2024)
150.
- Abstract
- This doctoral thesis presents the work the practical verification of a cooling concept involving direct air cooling of hollow windings for electric machines. The focus is on rotor windings for electrically excited synchronous machines for traction of electric vehicles. The work describes the cooling concept and compares it with the most common cooling concepts used today. The design of a experimental prototype includes the design of a modular dovetail joint rotor core to enable the installation of prewound coils.
The prototype is tested in order to verify the cooling concept. Experimentally a continuous rotor current of 175 A per turn is achieved with a winding hotspot temperature of 150 ∘C at an airflow of 1800 l/min. This... (More) - This doctoral thesis presents the work the practical verification of a cooling concept involving direct air cooling of hollow windings for electric machines. The focus is on rotor windings for electrically excited synchronous machines for traction of electric vehicles. The work describes the cooling concept and compares it with the most common cooling concepts used today. The design of a experimental prototype includes the design of a modular dovetail joint rotor core to enable the installation of prewound coils.
The prototype is tested in order to verify the cooling concept. Experimentally a continuous rotor current of 175 A per turn is achieved with a winding hotspot temperature of 150 ∘C at an airflow of 1800 l/min. This corresponds to a copper current density of 21 A/mm2. The thermal behavior is assessed with the help of a theoretical model which is validated with the experimental measurements. The model predicts that the prototype could handle a continuous current of 213 A per turn with a winding hotspot temperature of 155 ∘C at an airflow of 3200 l/min, which corresponds to a copper current density of 25 A/mm2.
With this maximum rotor current the electromagnetic performance of the electrically excited machine is compared to a permanent magnet machine
through finite element simulations. The results show that the electrically excited machine can produce a higher peak torque, but with a lower overall efficiency. However, the efficiency of some operating points above base speed, the electrically excited machine is higher, which means that it could be more efficient over drive-cycles operating much in those operating points, such as those representative of heavyduty trucks. Among the conclusions it is stated that with sufficient cooling (such as that provided by the cooling concept in this work) the electrically excited machine can help relieve the electric vehicle market from its dependency of rare earth elements. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/243534e1-71b1-4d7e-b021-5c59b2698218
- author
- Estenlund, Samuel
LU
- supervisor
-
- Mats Alaküla LU
- Avo Reinap LU
- Fran Marquez LU
- opponent
-
- Assoc. Prof. Lindh, Pia, Lappeenranta University of Technology, Finland.
- organization
- publishing date
- 2024-05-20
- type
- Thesis
- publication status
- published
- subject
- keywords
- Direct cooling, Electrical vehicle, Electrically excited machine
- volume
- 150
- edition
- 1
- pages
- 196 pages
- publisher
- Division of Industrial Electrical Engineering and Automation, Faculty of Engineering, Lund University
- defense location
- Lecture Hall M:A, building M, Ole Römers väg 1, Faculty of Engineering LTH, Lund University, Lund.
- defense date
- 2024-06-14 09:00:00
- ISBN
- 978-91-985109-9-7
- 978-91-985109-8-0
- language
- Swedish
- LU publication?
- yes
- id
- 243534e1-71b1-4d7e-b021-5c59b2698218
- date added to LUP
- 2024-05-20 11:19:48
- date last changed
- 2024-09-27 11:04:57
@phdthesis{243534e1-71b1-4d7e-b021-5c59b2698218,
abstract = {{This doctoral thesis presents the work the practical verification of a cooling concept involving direct air cooling of hollow windings for electric machines. The focus is on rotor windings for electrically excited synchronous machines for traction of electric vehicles. The work describes the cooling concept and compares it with the most common cooling concepts used today. The design of a experimental prototype includes the design of a modular dovetail joint rotor core to enable the installation of prewound coils. <br/><br/>The prototype is tested in order to verify the cooling concept. Experimentally a continuous rotor current of 175 A per turn is achieved with a winding hotspot temperature of 150 ∘C at an airflow of 1800 l/min. This corresponds to a copper current density of 21 A/mm2. The thermal behavior is assessed with the help of a theoretical model which is validated with the experimental measurements. The model predicts that the prototype could handle a continuous current of 213 A per turn with a winding hotspot temperature of 155 ∘C at an airflow of 3200 l/min, which corresponds to a copper current density of 25 A/mm2.<br/><br/>With this maximum rotor current the electromagnetic performance of the electrically excited machine is compared to a permanent magnet machine <br/> through finite element simulations. The results show that the electrically excited machine can produce a higher peak torque, but with a lower overall efficiency. However, the efficiency of some operating points above base speed, the electrically excited machine is higher, which means that it could be more efficient over drive-cycles operating much in those operating points, such as those representative of heavyduty trucks. Among the conclusions it is stated that with sufficient cooling (such as that provided by the cooling concept in this work) the electrically excited machine can help relieve the electric vehicle market from its dependency of rare earth elements.}},
author = {{Estenlund, Samuel}},
isbn = {{978-91-985109-9-7}},
keywords = {{Direct cooling; Electrical vehicle; Electrically excited machine}},
language = {{swe}},
month = {{05}},
publisher = {{Division of Industrial Electrical Engineering and Automation, Faculty of Engineering, Lund University}},
school = {{Lund University}},
title = {{Direct air cooled hollow windings : Performance enhancement of electrically excited machines}},
url = {{https://lup.lub.lu.se/search/files/183796165/opponent_och_e-spik_ex.pdf}},
volume = {{150}},
year = {{2024}},
}