Performance Assessment of Standard Cooling Strategies for Hairpin Windings

This paper aims to assess the performance of some standard cooling strategies which are commonly used in traction electric motors for electric vehicles (EVs) employing hairpin windings. The use of such type of coils does normally lead to higher power dense designs, given the higher slot fill factors achievable; indeed the thermal management might become more challenging. The structured nature of the hairpin offers some opportunities from the cooling perspective but at the same time it might have some downsides, depending on the cooling option employed. In this work, two hairpin wound stators are taken into consideration, one with only two layer and another one with eight layers. Standard cooling strategies such as oil spray, water jacket and potting are being considered and the thermal behavior of each design is investigated. The thermal analyses are carried out numerically with the use of Computational Fluidynamics (CFD), including both fluid flow and heat transfer. The results allowed identifying the most appropriate cooling option in each design and provided useful input on how to maximise the heat dissipation.