Electromagnetic and Calorimetric Validation of a Direct Oil Cooled Tooth Coil Winding PM Machine for Traction Application
Journal article, 2020

Tooth coil winding machines offer a low cost manufacturing process, high efficiency and high power density, making these attractive for traction applications. Using direct oil cooling in combination with tooth coil windings is an effective way of reaching higher power densities compared to an external cooling jacket. In this paper, the validation of the electromagnetic design for an automotive 600 V, 50 kW tooth coil winding traction machine is presented. The design process is a combination of an analytical sizing process and FEA optimization. It is shown that removing iron in the stator yoke for cooling channels does not affect electromagnetic performance significantly. In a previous publication, the machine is shown to be thermally capable of 25 A/mm2 (105 Nm) continuously, and 35 A/mm2 (140 Nm) during a 10 s peak with 6 l/min oil cooling. In this paper, inductance, torque and back EMF are measured and compared with FEA results showing very good agreement with the numerical design. Furthermore, the efficiency of the machine is validated by direct loss measurements, using a custom built calorimetric set-up in six operating points with an agreement within 0.9 units of percent between FEA and measured results.

Efficiency validation

Performance evaluation

Electromagnetic design

Oil cooling

Permanent magnet machines

Calorimetric measurement

Model verification


Alessandro Acquaviva

Chalmers, Electrical Engineering, Electric Power Engineering

Stefan Skoog

Chalmers, Electrical Engineering, Electric Power Engineering

Emma Grunditz

Chalmers, Electrical Engineering, Electric Power Engineering

Torbjörn Thiringer

Chalmers, Electrical Engineering, Electric Power Engineering


1996-1073 (ISSN) 19961073 (eISSN)

Vol. 13 13 3339

Subject Categories

Mechanical Engineering

Energy Engineering

Other Electrical Engineering, Electronic Engineering, Information Engineering



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