Innovative Cooling Concepts
The continuous power density of the electric machines depends mainly on the cooling performance. With a good design of the electric machine and a water jacket cooling it´s possible to achieve continuous power densities over 5 kW/kg.
For improved cooling performance a direct oil cooling of the winding heads can be used. In the measurements it was possible to dissipate more than 4 times the losses by applying an oil cooling of the and winding head.
On most applications however, the numerous disadvantages of oil cooling overweigh. Oil has significantly worse cooling properties than water/glycol. Due to the fact that the windings of the electric machines can be directly cooled with oil, this leads to a better heat dissipation inside the machine. However, if the total expense for fluid/air heat exchangers, pumps and other cooling components is considered, the oil cooling not the best choice for all applications. For most application we recommend a water cooling system.
A possible solution to this problem is an integrated cooling concept, which has been used on the SC41. The cooling medium is in this case water/glycol. With the usage of complete isolated cooling channels oinside the slots a high continuous power density can be achieved. Due to the lower copper temperatures, the losses during middle and high loads can compensate the decrease in copper cross section area. Because of the lower weight and high efficiency cycle efficiency for automotive applications is increased. This cooling concept is only applicable for single tooth windings. It cannot be combined with the SciMo high filling factor winding for distributed winding designs.