Direct Liquid Cooling Method Verified with a Permanent-Magnet Traction Motor in a Bus

Direct liquid cooling of electrical machines is inherently the most efficient way of machine cooling in cases where the stator Joule losses are dominating. Removing the heat directly from where it is generated offers the most straightforward way for cooling in applications where the motors operate at elevated tangential stress during certain periods. This paper studies the feasibility of the direct liquid cooling using a radial flux permanent magnet motor as an example. The easiest way to provide experimental data was to install a directly liquid cooled motor is a test bus with which typical bus load cycles were tested.