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Volume & Efficiency Improvements for an Integrated Motor Drive

Challenge:

A customers development project involved creating a compact and lightweight intgrated inverter and motor for a high perfomance automotive application. Within the overall fixed casing envelope, compartments were allocated for the electric motor and power converter sections.

This high power density drive required a compact power inverter to be designed. A reliable cooling system for the was critical to meet the power output and reliability criteria.

As a result of the design constraints, several technical challenges arose:

  • Close proximity of power devices leading to concentration of high heat generation
  • Coolant channel packaging space restricted due to volume reduction
  • Coolant Pressure Drop was constrained to allow feed from the casing water jacket with minimal coolant pump power consumption
Diagram indicating the space allocated for power converter in the integrated drive

Analysis & Innovation:

ECS’ application knowledge in the automotive sector facilitated a detailed understanding of the product and technical constraints. Following technical workshop with the client, ECS devised a detailed thermal analysis plan consisting of:

  • Calculation of heat rejection across the drive cycle – identify critical operating points
  • CFD Model Set-up:
    • Define & create an optimised mesh, balancing precision vs. simulation time
    • Create model from an existing ECS template – these offer technically proven, time-efficient routes to model creation
  • Identification of cooling design optimisation opportunities:
    • Cooling Channel Design: Series/Parallel flow paths, serpentines, turbulators
    • Material selections to maximise thermal conductivity, coolant flow
  •  High precision CFD evaluation of shortlisted design optimisations to validate the design throughout the full operating range & drive cycles
Coolant Flow Path Optimisation showing coolant flow below the substrate
Component Temperature Prediction showing device temperatures during peak heat loss
Results Achieved:

As a result of the detailed analyses performed, ECS delivered to the client:

  • Confirmation that the feasibility of designing a cooling challenge within the prescribed space could be achieved
  • A range of design solutions which meet the specification, with recomendations on best solution
  • Full simulation data supporting conclusions to drive client decision making
  • A list of opportunities for future optimisation of the product – coolant pump (variable flow), alternative materials coolant channels

Knowledge of effective liquid cooling techniques allowed ECS to arrive at a highly compact cooler for an integrated drive power converter.
A detailed CFD analysis ensured an optimal design was achieved, ensuring device temperatures remained within limit whilst matching the coolant pressure drop to coolant pump requirements.