A two-phase HVAC-integrated cooling system for traction motors: modelling and performance analysis

Two-phase fluid flows have been regarded as a candidate cooling method for electric motors in order to boost torque density. Low-temperature, two-phase refrigerant is inherently available in vapour-compression Heat Ventilation Air Conditioning (HVAC) systems which are typically on-board vehicles. This paper explores the potential of bleeding a refrigerant fraction from the HVAC vapour-compression “core” cycle and feed it into the traction motor windings to achieve a radical cooling. In order to evaluate the features and performance of this integrated two-phase motor cooling concept, the paper proposes a simplified modelling technique that integrates the HVAC vapour compression cycle with the motor cooling sub-models. The objective is to assess the reduction in losses and the associated benefits in mitigating the extra burden on the motor and the oversizing requirements of the HVAC compressor.