Electrical Machine Coil Cooling with Axially Displaced Layers
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Solution Overview
Problem
The cooling of coils in electrical machines, particularly in direct drive wind turbines, is inefficient due to non-homogeneous heating and poor heat exchange at axial end portions, leading to potential coil failure and reduced generator efficiency.
Innovation Solution
The coils are designed with axially displaced layers, creating increased surface area and turbulence for improved cooling, combined with guiding structures to enhance heat exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling air is supplied axially through multiple inlets, then cooling of central portions of coils is improved, but cooling of axial end portions deteriorates due to poor heat exchange and air not following coil curvature
Solution Approach 1:
The cooling system is segmented into multiple independent cooling circuits, with separate inlets and outlets for different axial regions of the coils. This allows independent optimization of cooling flow for central and end portions, resolving the contradiction by enabling differentiated cooling strategies for different coil regions with varying thermal loads and geometric characteristics
Solution Approach 2:
Different cooling approaches are applied to different axial regions: central portions receive axial cooling airflow, while end portions receive radial cooling airflow that can properly contact the curved surfaces. This local differentiation resolves the contradiction by matching the cooling method to the specific thermal and geometric characteristics of each region
2Loss of energy
If cooling air flows axially through the air gap, then heat removal from coils is achieved, but temperature distribution becomes non-homogeneous with higher temperatures at outlet-side axial ends
Solution Approach 1:
The cooling system divides the airflow path into separate segments with independent temperature control. Fresh cooling air is supplied to both central and end regions through separate circuits, preventing the cumulative heating effect that occurs in single-pass axial flow. This segmentation maintains homogeneous temperature distribution while achieving effective heat removal
Solution Approach 2:
Instead of allowing cooling air to flow axially from inlet to outlet and progressively heat up, the system inverts the approach by supplying fresh cooling air radially to end portions independently of the axial flow path. This reversal of the cooling sequence ensures that all regions receive optimally cooled air, eliminating temperature non-uniformity while maintaining high heat removal efficiency
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 coils, reducing the risk of failure and enhancing generator efficiency by ensuring more uniform temperature distribution.
Implementation Method 1
a cooling fluid such as air may be run through the air gap separating the coils and the active elements of the rotor. The cooling fluid contacts the active element and takes heat away from them
Implementation Method 2
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
Figure 1
Figure 2
Figure 3~5B
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).