Convective Heat Transfer Coefficients and Mechanical Loss Evaluation of Oil Splashing in Direct Cooled Electrically Excited Hairpin Motors
Paper in proceeding, 2022

There in an increasing trend in the use of the direct oil cooling in electric motors for automotive because of the increasing demand of high power/torque density as well as overload capability. One of the most immediate solution is to fill the housing with some oil level and benefit of the heat transfer from the oil splashing. The mechanical losses coming from the rotor rotation are well known and they represent a significant challenge, especially at high speed and high oil level. Therefore, the derivation and prediction of these losses have not been properly investigated leading to a lack in the current literature. Moving Particles Simulation (MPS) method is used in Particleworks to calculate the mechanical losses caused by the oil viscosity and convective heat transfer coefficients (HTC) are extracted for a 250 kW Electrically Excited Synchronous Machine at different speeds and oil levels.


Traction Motors

Direct Oil Cooling



Electrically Excited Synchronous Machine (EESM)


Electric Motors

Heat Transfer Co- efficient (HTC)


Luca Boscaglia

Chalmers, Electrical Engineering, Electric Power Engineering

Yujing Liu

Chalmers, Electrical Engineering, Electric Power Engineering

Hasan Avsar

EnginSoft SpA

Junfei Tang

Chalmers, Electrical Engineering, Electric Power Engineering

Massimo Galbiati

EnginSoft SpA

2022 International Conference on Electrical Machines, ICEM 2022

9781665414326 (ISBN)

2022 International Conference on Electrical Machines (ICEM)
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Energy Engineering

Energy Systems



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