Immersion Cooled Motor Controller Thermal Management
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Solution Overview
Problem
Aerospace power electronic converters face challenges in managing high power density and thermal management due to excessive heating in bulk capacitors and MOSFETs, which can lead to safety and reliability issues.
Innovation Solution
An immersion cooled AC/AC motor controller with a sealed housing containing non-conductive fluorocarbon cooling liquid and vertically mounted power semiconductor switches with individual heat sinks, along with finned heat sinks and low-density filler material to enhance cooling efficiency and reduce weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If bulk film capacitors are sized by current rating to provide reactive current, then the power electronic converter can operate at high power levels, but excessive heating and internal hot spots occur leading to thermal limitations
Solution Approach 1:
The patent applies liquid immersion cooling by submerging power electronic components (MOSFETs, capacitors, inductors) in a non-conductive cooling liquid within a sealed housing. This hydraulic cooling method efficiently removes heat from high-power components, enabling operation at power levels greater than 30 kW while maintaining safe operating temperatures without air cooling limitations
Solution Approach 2:
The patent changes the thermal management parameter from air cooling to liquid immersion cooling, and modifies component specifications (e.g., using 14 AWG wire for inductors) to optimize performance in the immersion cooling environment, allowing sustained high power operation without thermal runaway
2Temperature
If MOSFETs are mounted to heat sinks for cooling, then heat dissipation is improved, but the device complexity and space requirements increase
Solution Approach 1:
The patent merges the cooling function into the housing structure itself by creating an immersion cooling system where the housing contains both the electronic components and the cooling liquid. This eliminates the need for separate heat sinks and complex cooling assemblies, reducing device complexity while maintaining effective heat dissipation
Solution Approach 2:
The housing serves multiple functions: it provides structural enclosure, contains the cooling liquid, and acts as a thermal management system. This multi-functionality eliminates the need for separate cooling components, reducing overall device complexity while maintaining effective heat dissipation
3Power
If immersion cooling is incorporated to support high power density requirements, then thermal management is improved, but the size and weight of the convertor may increase
Solution Approach 1:
The patent uses non-conductive fluorocarbon cooling liquid which has favorable thermal properties and low density, and optimizes the immersion cooling system parameters to achieve efficient heat removal with minimal liquid volume, thereby reducing weight while maintaining high power density capability
Solution Approach 2:
The patent applies immersion cooling selectively to the high-heat-generating components (power board module with MOSFETs, bulk capacitors, inductors) within the housing, rather than cooling the entire assembly. This localized approach minimizes the volume and weight of cooling liquid required while effectively managing heat from critical components
4Power
If inductors are constructed with heavier wire gauge to handle high currents, then current carrying capacity is improved, but the weight and volume of the convertor increase
Solution Approach 1:
The immersion cooling environment allows the use of lighter wire gauge (14 AWG) for inductor construction because the liquid cooling efficiently removes heat from the wire windings, enabling higher current densities without thermal damage. This reduces inductor weight and volume while maintaining adequate current carrying capacity for high-power operation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves increased power density and weight savings by efficiently managing heat through nucleated boiling and forced air cooling, allowing for higher power dissipation and reduced wire gauge usage, while maintaining safe operating temperatures and eliminating fire risks.
Implementation Method 1
efficiently managing heat through nucleated boiling
Implementation Method 2
efficiently managing heat through nucleated boiling and forced air cooling
Implementation Method 3
Each switch may have an individual heat sink operatively associated therewith to increase the surface area that is available for cooling in the liquid
Data Source
Figure 1
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AI summary
An immersion cooled motor controller assembly (10) is disclosed that includes a sealed housing (12), a fluorocarbon cooling liquid (60) contained in the sealed housing, and an AC/AC motor controller (30) disposed in the sealed housing and submerged in the fluorocarbon cooling liquid, wherein the AC/AC motor controller includes a power board module (32) adapted and configured to operate at power levels greater than 30 kW.