High Performance Cooling of Traction Brushless Machines
Doktorsavhandling, 2021

The work presented in this thesis covers several aspects of traction electric drive system design. Particular attention is given to the traction electrical machine with focus on the cooling solution, thermal modelling and testing.

A 60 kW peak power traction machine is designed to achieve high power density and high efficiency thanks to direct oil cooling. The machine selected has a tooth coil winding, also defined as non-overlapping fractional slot concentrated winding. This winding concept is state of the art for many applications with high volumes and powers below 10 kW. Also, these have been proven successful in high power applications such as wind power generators. In this thesis, it is shown that this technology is promising also for traction machines and, with some suggested design solutions, can present certain unique advantages when it comes to manufacturing and cooling.

The traction machine in this work is designed for a small two-seater electric vehicle but could as well be used in a parallel hybrid. The proposed solution has the advantage of having a simple winding design and of integrating the cooling within the stator slot and core. A prototype of the machine has been built and tested, showing that the machine can operate with current densities of up to 35 A/mm^2 for 30 seconds and 25 A/mm^2 continuously. This results in a net power density of the built prototype of 24 kW/l and a gross power density of 8 kW/l with a peak efficiency above 94%. It is shown that a version of the same design optimized for mass manufacturing has the potential of having a gross power density of 15.5 kW/l which would be comparable with the best in class traction machines found on the automotive industry.

The cooling solution proposed is resulting in significantly lower winding temperature and an efficiency gain between 1.5% and 3.5% points, depending on the drivecycle, compared to an external jacket cooling, which is a common solution for traction motors.

drivetrain system analysis.

energy efficiency


electrical machine design

permanent magnet synchronous machine (PMSM)

Online via Zoom
Opponent: Juha Pyrhönen


Alessandro Acquaviva

Chalmers, Elektroteknik, Elkraftteknik

Sizing and energy efficiency analysis of a multi-phase FSCW PMSM drive for traction application

IECON Proceedings (Industrial Electronics Conference),; Vol. 2020-October(2020)p. 2069-2074

Paper i proceeding

Manufacturing of tooth coil winding PM machines with in-slot oil cooling

2020 International Conference on Electrical Machines (ICEM),; (2020)p. 2314-2320

Paper i proceeding

Analytical Conduction Loss Calculation of a MOSFET Three-Phase Inverter Accounting for the Reverse Conduction and the Blanking Time

IEEE Transactions on Industrial Electronics,; Vol. 68(2021)p. 6682-6691

Artikel i vetenskaplig tidskrift

Design and Verification of In-slot Oil-Cooled Tooth Coil Winding PM Machine for Traction Application

IEEE Transactions on Industrial Electronics,; Vol. 68(2021)p. 3719-3727

Artikel i vetenskaplig tidskrift

Computationally Efficient Modeling of Electrical Machines With Cooling Jacket

IEEE Transactions on Transportation Electrification,; Vol. 5(2019)p. 618-629

Artikel i vetenskaplig tidskrift

Comparison of MTPA and Minimum Loss Control for Tooth Coil Winding PMSM Considering PM and Inverter Losses


Paper i proceeding

Pole-Slot Selection Considerations for Double Layer Three-phase Tooth-Coil Wound Electrical Machines

2018 XIII International Conference on Electrical Machines (ICEM),; (2018)p. 934-940

Paper i proceeding

Coupled 3-D Thermal and Electromagnetic Modelling of a Liquid-cooled Transverse Flux Traction Motor

Proceedings - 2018 23rd International Conference on Electrical Machines, ICEM 2018,; (2018)p. 2640-2646

Paper i proceeding

Analytical Electromagnetic Sizing of Inner Rotor Brushless PM Machines Based on Split Ratio Optimization

2018 XIII International Conference on Electrical Machines (ICEM),; (2018)p. 576-582

Paper i proceeding

Energy efficiency of a SiC MOSFET propulsion inverter accounting for the MOSFET's reverse conduction and the blanking time

2017 19th European Conference on Power Electronics and Applications,; (2017)

Paper i proceeding




Elektroteknik och elektronik

Annan elektroteknik och elektronik



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4900



Online via Zoom


Opponent: Juha Pyrhönen

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