Electrical Machine Coil Cooling With Axially Displaced End Layers
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Solution Overview
Problem
Existing cooling systems for electrical machine coils, particularly in direct drive wind turbines, fail to uniformly cool the axial end portions of the coils due to non-homogeneous heating and inadequate contact with cooling fluid, leading to temperature-related failures and efficiency limitations.
Innovation Solution
The coils are designed with axially displaced layers, creating irregular end portions that enhance surface exposure to cooling fluid and induce turbulence, improving cooling efficiency and stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling fluid is run through the air gap to cool the coils, then the temperature of the coils is reduced, but the axial end portions of the coils close to the outlets are not cooled effectively due to heated cooling air and poor contact
Solution Approach 1:
The patent introduces a radial component to the cooling fluid flow by providing cooling channels in the teeth that extend radially outward. This adds a new dimension (radial direction) to the cooling approach, allowing cooling fluid to reach the axial end portions of the coils from the radial direction rather than only from the axial direction. This multi-dimensional cooling approach overcomes the limitation of single-direction cooling where heated air cannot effectively cool the end portions.
Solution Approach 2:
The teeth are configured to act as intermediaries that conduct cooling fluid from the air gap region to the axial end portions of the coils. The cooling channels in the teeth serve as intermediary pathways, transporting cooling fluid radially outward to the coil end portions, thereby enabling indirect cooling of areas that are difficult to reach with direct axial cooling flow.
2Loss of energy
If cooling air is supplied axially through inlets and outlets, then cooling is provided to the coils, but the cooling air heats up as it passes through and cannot effectively cool the axial end portions close to outlets
Solution Approach 1:
The cooling system is segmented into multiple independent cooling paths: axial cooling channels for the central portions of the coils and radial cooling channels in the teeth for the axial end portions. This segmentation allows different regions of the coils to be cooled by separate cooling fluid streams, preventing the problem where a single cooling stream becomes heated and ineffective for distant regions.
Solution Approach 2:
Different regions of the coils are provided with locally optimized cooling structures. The central portions receive axial cooling flow, while the axial end portions receive radial cooling flow through the teeth. This local differentiation ensures that each region receives cooling appropriate to its specific thermal requirements and cooling fluid temperature conditions.
3Reliability
If coils are wound tightly around teeth, then electrical insulation is improved, but heat dissipation at axial end portions is reduced due to poor contact with cooling fluid
Solution Approach 1:
The teeth with integrated cooling channels serve as intermediaries that deliver cooling fluid directly to the axial end portions of the coils. This intermediary cooling structure overcomes the limitation of tight winding that prevents direct cooling fluid contact, by providing a dedicated thermal pathway through the teeth to the coil ends.
Solution Approach 2:
The patent utilizes fluid dynamics principles by providing cooling channels that引导 cooling fluid flow radially outward through the teeth to the axial end portions of the coils. This hydraulic approach ensures continuous cooling fluid contact with the coil end portions, overcoming the poor heat dissipation caused by tight winding configurations.
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 design effectively cools the axial end portions of the coils, reducing the risk of damage and enhancing the operational efficiency of electrical machines by ensuring more uniform heat dissipation.
Implementation Method 1
The cooling fluid contacts the active element and takes heat away from them
Implementation Method 2
a cooling fluid such as air may be run through the air gap separating the coils and the active elements of the rotor
Implementation Method 3
the cooling air may not follow the curvature of the coils at these axial ends. I.e., the contact, and thus also the heat exchange, between the cooling air and the end portions of these coils may not be very good
Data Source
AI summary
The present disclosure relates to coils (121), electrical machines (100) comprising coils (121), e.g. a wind turbine generator (42), and methods for cooling coils (121) of electrical machines (100) and for winding and/or electrically insulating (200) coils (121). An electrical machine (100) comprises a rotor (110) and a stator (120). At least one of the rotor (110) and the stator (120) comprises a plurality of teeth (119) and a plurality of coils (121), the coils (121) comprising strand (150) which is wound around the teeth (119) in layers (130, 131). A first axial end portion of a first layer (130) of at least one of the coils (121) is axially displaced (117) with respect to a first axial end portion of a second layer (131) of the coil (121).