Direct liquid cooling in low-power electrical machines: Proof-of-concept

Pia M. Lindh*, Ilya Petrov, R. Scott Semken, Markku Niemela, Juha J. Pyrhonen, Lassi Aarniovuori, Toomas Vaimann, Ants Kallaste

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


This paper evaluates the feasibility of a direct liquid cooling approach in the thermal management of an axial flux permanent-magnet machine. To demonstrate the cooling method, a test motor was fitted with helical tooth coil windings formed from a hybrid conductor comprising a stainless steel coolant conduit tightly wrapped with a stranded Litz wire. The motor is a 100-kW permanent-magnet, axial-flux, double-stator, single-rotor machine. The proof of concept integrated the motor with a closed liquid coolant loop, appropriate instrumentation, and a data acquisition system. The general performance of the motor was examined at various power levels using polyalphaolefin oil as the cooling fluid. The results show the proposed cooling method to be feasible, and furthermore, to provide significant improvements to the machine thermal management.

Original languageEnglish
Article number7527616
Pages (from-to)1257-1266
Number of pages10
JournalIEEE Transactions on Energy Conversion
Issue number4
Early online date1 Aug 2016
Publication statusPublished - 1 Dec 2016


  • Electric machines
  • liquid cooling
  • permanent-magnet motors
  • rotating machines
  • temperature dependence


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