Dry Air Gap Cooling Structure for Rotating Electrical Machines
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Solution Overview
Problem
Existing large motors and generators with oil or coolant-filled air gaps suffer from viscous losses, heating, and potential cavitation damage due to turbulence, which are not effectively addressed by prior configurations.
Innovation Solution
A fluid-cooled, rotating electrical machine with a dry air gap and a fluid-tight barrier isolates heat-transfer fluid from the gap, using heat pipe cooling for the rotor and conduits to return leaked fluid, and incorporates ascending and descending coolant channels for efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the air gap is filled with oil or coolant, then cooling effect is improved, but viscous losses and heating increase
Solution Approach 1:
The patent divides the machine into two distinct zones: a dry air gap region and a fluid-filled stator winding region. The fluid-tight barrier segments the cooling fluid containment to the stator windings only, preventing fluid presence in the air gap. This segmentation allows the air gap to remain free of fluid (reducing viscous losses) while the stator windings receive adequate cooling through the contained fluid.
Solution Approach 2:
The patent introduces a fluid-tight barrier as an intermediary component between the stator windings and the air gap. This barrier mediates the cooling process by containing the cooling fluid within the stator winding region while preventing its presence in the air gap, thus enabling cooling without the harmful effects of fluid in the air gap.
2Temperature
If coolant is present in the air gap, then cooling is enhanced, but cavitation damage and turbulence occur
Solution Approach 1:
The patent segments the machine structure to separate the cooling fluid containment zone (stator windings) from the air gap zone. The fluid-tight barrier creates distinct compartments, allowing cooling to occur in the stator windings while maintaining a dry, turbulence-free environment in the air gap, thereby preventing cavitation damage.
Solution Approach 2:
The fluid-tight barrier acts as an intermediary that enables cooling of the stator windings while preventing the cooling fluid from entering the air gap. This mediation ensures that the benefits of cooling are achieved without exposing the air gap components to cavitation and turbulence hazards.
3Reliability
If fluid-tight barrier is added, then fluid isolation is improved, but device complexity increases
Solution Approach 1:
The patent employs a fluid-tight barrier in the form of flexible membranes or thin film structures that conform to the stator winding geometry. These thin-film barriers provide effective fluid isolation without adding significant structural complexity or rigid components, maintaining simplicity while ensuring reliable fluid containment.
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 configuration reduces viscous losses and cavitation risk while enhancing cooling efficiency, maintaining high performance and reducing operational costs.
Implementation Method 1
heat pipe cooling for the rotor
Implementation Method 2
ascending and descending coolant channels for efficient heat transfer
Data Source
AI summary
A fluid-cooled, rotating electrical machine having a dry air gap. The rotating electrical machine includes a rotor assembly, a stator assembly, an annular air gap, and a fluid-tight barrier. The stator assembly is on a common center with the rotor assembly and has a stator core, stator coils passing through the stator core that have stator end-coils, and an ascending coolant channel extending axially through the stator core. The air gap is radially between the stator assembly and the rotor assembly. The fluid-tight barrier between the stator end-coils and the air gap.