Direct-Cooled Stator Windings With Integrated Heat Pipes
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Solution Overview
Problem
Current cooling methods for high specific power electric machines, such as electric aircraft, face challenges due to high heat loading in windings, which limits the effectiveness of existing cooling systems, especially at high voltages or low air pressures.
Innovation Solution
The proposed solution involves integrating a heat exchanger with the winding conductors to provide direct cooling. This can be achieved by using hollow conductors with heat pipes inserted directly into them, or by routing heat pipes adjacent to solid or semi-open conductors. Additionally, additive manufacturing methods can simplify the fabrication of machine components, allowing for customization and closer contact between heat pipes or coolant flows and conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional cooling methods (cooling jackets, oil spray cooling, flooded stator cooling) are used, then the cooling system is simple to implement, but the thermal resistance between cooling medium and conductors is high, reducing cooling effectiveness
Solution Approach 1:
The cooling channels are integrated directly into the stator core structure, merging the cooling system with the magnetic circuit. This eliminates the thermal barrier of separate cooling jackets and enables direct contact between cooling medium and heat-generating conductors, reducing thermal resistance while maintaining manufacturing feasibility through unified core fabrication
Solution Approach 2:
Cooling channels are nested within the stator core laminations, with coolant flow paths embedded inside the magnetic circuit structure. This nested arrangement allows the cooling medium to access heat-generating regions directly through the core itself, eliminating external thermal barriers while maintaining a compact integrated design
2Temperature
If axial cooling channels inside slots are used, then direct cooling of windings is improved, but insulation thickness must be increased, reducing slot fill factor and increasing conductor losses
Solution Approach 1:
Cooling channels are positioned specifically in regions where heat generation is highest (near conductors and windings), providing localized cooling where most needed. This targeted approach eliminates the need for uniform insulation thickening across the entire slot, maintaining slot fill factor by applying cooling only where thermal management is critical
Solution Approach 2:
The cooling approach transitions from radial or external cooling to axial cooling channels positioned within slot regions, utilizing the axial dimension of the stator core. This dimensional shift allows cooling medium to access winding heat directly without requiring increased radial insulation thickness, preserving slot fill factor while achieving effective cooling
3Reliability
If high voltage insulation thickness is increased to provide sufficient dielectric strength, then electrical insulation is improved, but thermal resistance between winding losses and cooling fluid increases, reducing cooling effectiveness
Solution Approach 1:
The cooling system is merged with the stator core magnetic circuit, positioning cooling channels in direct thermal contact with heat-generating conductors. This integration eliminates the need for thick insulation barriers between cooling fluid and windings, as the cooling medium accesses heat directly through the core structure itself, maintaining dielectric strength while minimizing thermal resistance
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 direct cooling method effectively reduces heat generation in windings, improving cooling efficiency compared to traditional methods. It is also insensitive to machine size, voltage, and insulation thickness, making it applicable across various machine geometries and operating conditions.
Implementation Method 1
heat pipes inserted directly into them
Implementation Method 2
heat pipes routed directly adjacent and in close proximity to solid or semi-open conductors
Implementation Method 3
fluids can be routed through hollow conductors in the winding
Data Source
AI summary
A stator winding includes a plurality of conductors including ducts. The ducts can be connected to a heat pipe or a conduit providing a coolant flow to directly cool the winding. The heat pipe can be connected to a heat exchanger that includes a coolant flow. The stator winding can be produced using additive manufacturing, with hollow ducts extending through leg sections and solid end sections. The heat exchanger can also be additively manufactured. A circuit for driving an electrical machine can be in thermal communication with the heat exchanger, such that the thermal system manages both the stators and the drive circuit.