Inverter Heat Sink Thermal Analysis of a Fully Integrated, 3-in-1 Electric Drive Unit (EDU) 2022-01-0666

Over the years, requirements for an electric drive for traction applications have increased substantially in terms of efficiency, power density, packaging space and cost. Manufacturers have employed various strategies to achieve high efficiency and power dense solutions. One such strategy is to use a synergistic approach by combining typical EDU sub-components such as an inverter, a motor and a gearbox with a differential to form a fully integrated 3-in-1 solution. Electrical and thermal losses from such a system can be quite significant as it includes losses from the inverter, the motor and the gearbox. As a result, thermal performance is often a limiting factor in improving the packaging space and power density. To address thermal issues, an effective liquid cooling system must be employed that ensures sufficient heat dissipation from all of the EDU subcomponents and helps to reduce packaging space.

Although there are multiple thermal management solutions to cool the inverter, motor and gearbox, this paper discusses a one-fluid approach. Specifically, it discusses thermal modeling of a forced oil-cooling strategy in the EDU at system level with emphasis on the inverter heat sink efficiency and cooling. Three-dimensional computational fluid dynamics (CFD) conjugate heat transfer (CHT) simulations were carried out to investigate flow, pressure loss and heat transfer. Initially, the computational model was validated with bench test data in terms of pressure loss and thermal data for a specific oil flow rate and temperature. Later, the effect of fin arrangement, shape, diameter and coolant flow routing channels on heat transfer and pressure loss are investigated and discussed.