Airgap Cooling Passages for Rotor Temperature Uniformity
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Solution Overview
Problem
High power density electric machines face thermal management challenges due to heat generation, leading to inefficiencies, component degradation, and potential failure, especially in high-speed operations where conventional cooling methods fail to maintain uniform temperatures and material integrity.
Innovation Solution
A direct cooling system is implemented within the airgap of electric machines using a new cooling circuit routed through interdigitated armature laminations, with cooling manifolds and axial holes delivering cooling fluids to the rotor assembly, effectively reducing thermal energy build-up and temperature non-uniformities across the rotor system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high power density electric machines are designed with larger power outputs and smaller machine sizes, then power output and power density are improved, but thermal management becomes more demanding and heat removal becomes difficult
Solution Approach 1:
The cooling circuit is nested within the airgap between the rotor and stator, with cooling channels formed inside the rotor assembly structure itself. The cooling fluid flows through channels defined by the rotor yoke and rotor magnets, effectively nesting the cooling system within the existing machine structure rather than adding external cooling components.
Solution Approach 2:
A cooling fluid acts as an intermediary medium to transfer heat away from the rotor components. The cooling fluid flows through the airgap cooling circuit, absorbing heat from the rotor yoke and rotor magnets, and carrying it away to external cooling systems, thus mediating the thermal management function.
2Speed
If conventional cooling methods are used in high-speed operations, then cooling is provided, but uniform temperature distribution is not maintained and material integrity deteriorates
Solution Approach 1:
The cooling circuit is designed to provide localized cooling at specific hot spots within the rotor assembly. Cooling channels are positioned to directly cool the rotor yoke and rotor magnets where heat generation is highest, ensuring that critical components maintain appropriate temperature levels even during high-speed operation.
Solution Approach 2:
The cooling fluid flows continuously through the cooling channels in the rotor assembly, providing uninterrupted cooling during high-speed operation. This continuous cooling action maintains uniform temperature distribution and prevents thermal buildup that would compromise material integrity at high operating speeds.
3Loss of energy
If cooling circuits are routed through interdigitated armature laminations with manifolds and axial holes, then cooling efficiency is improved, but device complexity increases
Solution Approach 1:
The cooling circuit functionality is merged with the existing armature lamination structure. The interdigitated laminations themselves form the cooling channels, and the rotor yoke structure incorporates the cooling manifolds and axial holes, combining the structural and cooling functions into a single integrated design rather than adding separate cooling components.
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
This approach enhances cooling efficiency, maintains uniform temperatures, and prevents material integrity issues, enabling higher speed operations and improved power density without compromising the mechanical or magnetic strength of the rotor components.
Implementation Method 1
a cooling fluid supply configured to provide a cooling fluid to the airgap
Implementation Method 2
effectively reducing thermal energy build-up and temperature non-uniformities across the rotor system
Data Source
AI summary
An airgap cooling system (140) for an electric machine (100), the electric machine (100) including a rotor assembly (102) rotatably mounted within a stator assembly (120) and defining an airgap (130) therebetween, wherein the stator assembly (120) comprises a lamination stack (124). The airgap cooling system (140) includes a plurality of distribution passages (142) that extend through the lamination stack (124); a plurality of discharge passages (150) that extend between the plurality of distribution passages (142) and the airgap (130); a cooling manifold (160) defining an annular distribution plenum (164) in fluid communication with the plurality of distribution passages (142), wherein the cooling manifold (160) is configured for receiving a cooling fluid (144) and directing the cooling fluid (144) into the distribution plenum (164), through the distribution passage (142) and the discharge passage (150), and into the airgap (130).