New Oil-Flooded Direct Stator Cooling System for High Power Density Machines With Hairpin Windings

High power density machines are essential in sectors such as aeronautics, automotive and traction. In order to achieve high power densities, cooling systems that are capable of extracting large amounts of heat are required. In this regard, direct cooling systems, in which the stator conductors are in contact with the cooling fluid, are the most promising. For this reason, this paper presents a new direct flooded stator cooling system specifically aimed at conventional plug-in hairpin winding machines. Unlike other cooling systems, the proposed one presents a solution with channels between all its conductors and not only at the top or bottom of the slot. To demonstrate the capabilities of the proposed cooling system, a motorette has been manufactured and experimentally validated. The main characteristics of this cooling system are described, its potential is evaluated by applying it to a 250 kW and 10,000 rpm conceptual aeronautical motor design and, additionally, design guidelines for the sizing of equivalent cooling systems are given.