Air-Gap Cooling Flow Reversal for Wind Turbine Generators
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Solution Overview
Problem
Existing cooling systems for electrical machines, particularly in direct drive wind turbines, fail to effectively distribute heat, leading to overheating and reduced efficiency of active rotor and stator elements, which can result in failure and require frequent repairs.
Innovation Solution
A method and system that reverses the direction of cooling fluid flow through the air gap between rotor and stator elements, distributing heat more evenly and reducing hot spots by alternating the cooling fluid's direction of travel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling fluid flows in a single direction through the air gap, then cooling is provided to active elements, but temperature hotspots develop and heat distribution is uneven
Solution Approach 1:
The cooling fluid flow direction is periodically reversed through the air gap. The system alternates between forward flow and reverse flow modes, creating periodic action that prevents permanent hotspot formation. This periodic reversal ensures that different regions of the active elements are cooled at different times, achieving more uniform temperature distribution across all components.
Solution Approach 2:
The cooling system inverts the conventional single-direction cooling approach by implementing bidirectional flow. The cooling fluid is directed through the air gap in one direction, then reversed to flow through the same gap in the opposite direction. This inversion strategy ensures that regions receiving less cooling in one direction receive enhanced cooling when the flow reverses, thereby eliminating temperature hotspots and extending the service life of active elements.
2Temperature
If cooling fluid is continuously supplied in one direction, then heat is removed from active elements, but the same regions are over-cooled while other regions remain hot
Solution Approach 1:
The system employs periodic reversal of cooling fluid flow direction to achieve uniform temperature distribution. By alternating between forward and reverse flow cycles, the system ensures that all regions of the active elements receive adequate cooling over time, preventing both overheating and excessive cooling of specific zones. This enables higher power output capability while maintaining temperature uniformity.
Solution Approach 2:
The cooling system transitions from a static single-direction flow to a dynamic bidirectional flow system. The flow direction is actively controlled and reversed based on operational requirements, allowing the system to adaptively distribute cooling across different regions. This dynamic approach optimizes heat removal efficiency and maintains temperature uniformity, thereby enabling increased power output.
3Device complexity
If a simple single-direction cooling system is used, then the system complexity is low, but temperature hotspots reduce efficiency
Solution Approach 1:
The cooling system incorporates periodic flow reversal with minimal additional complexity. By using controllable valves or pumps that can switch flow direction, the system achieves bidirectional cooling without requiring completely separate cooling circuits. This periodic action eliminates temperature hotspots that would otherwise reduce generator efficiency, while maintaining relatively simple system architecture.
Solution Approach 2:
The system inverts the conventional single-direction cooling paradigm by implementing reverse flow capability through the same cooling circuit. This is achieved by strategically placing flow control elements that can redirect the cooling fluid through the air gap in opposite directions. The inversion approach eliminates hotspots and improves generator efficiency without substantially increasing device complexity.
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 extends the service life of insulation by up to 100% and increases power output by maintaining active elements at higher temperatures for shorter periods, reducing the need for repairs and enhancing overall machine performance.
Implementation Method 1
The cooling fluid contacts the active elements and takes heat from them away
Implementation Method 2
a cooling fluid may be run through the air gap separating the active elements. The cooling fluid contacts the active elements and takes heat from them away
Data Source
Figure 1
Figure 2
Figure 3~4A
AI summary
The present disclosure relates to electrical machines, cooling systems and methods for cooling active elements of electrical machines. More in particular, the present disclosure relates to cooling systems and methods for cooling active rotor and/or stator elements of a generator of a wind turbine, e.g. of a direct drive wind turbine. A cooling method comprises supplying a cooling fluid to an air gap through one or more primary inlets of an electrical machine for cooling a plurality of active elements of a rotor of the electrical machine and/or a plurality of active elements of a stator of the electrical machine separated by the air gap. The method further comprises reversing a direction of flow of the cooling fluid such that the cooling fluid is extracted from the electrical machine through one or more primary inlets.