Direct Driven Hydraulics: What can possibly go wrong? -A thermal analysis

T. Minav, L. Papini, Alexander Järf, K. Tammi, M. Pietola

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review


This paper focuses on a thermal analysis of Direct Driven Hydraulics (DDH). DDH combines the benefits of electric and hydraulic technologies in a compact package with high power density, superior performance and increased controllability. It enables a reduction of hydraulic losses therefore achieves better fuel efficiency. The main advantages of the presented architecture compared to a conventional valve-controlled system are the reduced hydraulic tubing and the amount of potential leakage points. DDH however represents a challenge for the prediction of the thermal behavior and its management as the temperature is a determining parameter of performance, lifespan, and safety of the system. Therefore, the electro-hydraulic model of a DDH involving a variable motor speed, two fixed-displacement internal gear pump/motors was developed at a system level for thermal analysis. In addition, losses dependent on temperature were validated by measurements under various operating conditions set by a cold chamber to 20, 10, and -5 °C. A model investigation predict heat dissipation from the electrical machine to the rest of the system. The electric machine heat dissipation plays an important role in the system temperature balance while the DDH is operated in extreme continuous operating condition. Furthermore, expected challenges for the future development of DDH concept are discussed.

Original languageEnglish
Title of host publicationProceedings - 2016 22nd International Conference on Electrical Machines, ICEM 2016
Number of pages7
ISBN (Electronic)9781509025381
Publication statusPublished - 2 Nov 2016
MoE publication typeA4 Article in a conference publication
EventInternational Conference on Electrical Machines - Lausanne, Switzerland
Duration: 4 Sep 20167 Sep 2016
Conference number: 22


ConferenceInternational Conference on Electrical Machines
Abbreviated titleICEM
Internet address


  • Decentralized hydraulics
  • direct driven hydraulics
  • efficiency
  • electric drives
  • hydraulic actuator
  • hydraulic drives
  • losses
  • off-road machinery
  • thermal losses

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