Direct Conductor Cooling in Concentrated Windings

This paper presents and assesses the cooling integration of electrical machines with concentrated windings. A conventional coil in a concentrated winding with forced cooling applied on the exterior coil surfaces is replaced by an alternative solution where the coil is opened up in a laminar structure with the intention of the coolant fluid penetrating the coil and removing the interior heat. This is a purely theoretical study where a set of FE models are used to evaluate the torque capability under elevated thermal loads, comparing conventional to alternative cooling integration topologies. The objective of the unsophisticated FE evaluation models and simple design rules is to demonstrate the potential of the laminated type of windings where the space between the current carrying flat conductors is used to circulate coolant so that the heat losses are removed in the vicinity of where they are generated. Conjugate heat transfer analysis in Comsol multiphysics based on 2D and 3D is used to demonstrate the cooling capability for air and oil cooled windings up to thermal loads corresponding to 50 A/mm²at 24 nΩm and a target hot spot temperature of 120°C for copper.