There is no doubt that electrics vehicles are the future. Their evolution has initialized a shift from physically separated motor and drive systems to integrated motor drives in which the motor and power electronics are embedded in the same housing. The major bottleneck for this integration is the increased heat dissipation in a reduced volume, resulting in very challenging cooling requirements. With conventional cooling methods, like liquid cooling and air cooling, a further increase in power density is not possible. Therefore, cooling by flow boiling is proposed. Flow boiling exhibits a high heat transfer and low pressure drop, but there is an inherent risk of dry-out when the critical heat flux is exceeded (left figure). Correlations exist which predict the heat transfer coefficient and critical heat flux for flow boiling in tubes. However, they assume a uniform and constant heat flux as boundary condition, which is not the case in integrated motor drives where the heat fluxes are transient and locally more intense. Therefore, new correlations for the heat transfer coefficient and critical heat flux should be developed that take temporally and spatially varying heat fluxes into account. For this purpose, an experimental test rig has been developed (see right figure).