External Corona Shielding for Electrical Machines
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Solution Overview
Problem
Conventional external corona protection in electrical machines, particularly in turbo generators, faces issues with delamination due to thermo-mechanical stresses, leading to potential partial discharges, and has a relatively large layer thickness.
Innovation Solution
A double-layer external corona protection system with sliding layers and viscoelastic connections, where each layer consists of an electrically conductive material with a sliding layer facing the other, allowing for mechanical decoupling and defined electrical contact, eliminating the need for a predetermined breaking layer and promoting thorough impregnation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a fixed mechanical connection is used between external corona protection and laminated core, then structural stability is improved, but delamination occurs due to thermo-mechanical stresses
Solution Approach 1:
The patent introduces a dynamic element (breaking point) that allows the structure to transition from a fixed state to a controlled failure state, accommodating thermal expansion differences between the conductor bar and laminated core while maintaining electrical connectivity through the conductive fleece
Solution Approach 2:
The breaking point is designed as a predetermined weak point that absorbs thermo-mechanical stresses before they can cause damage to the main insulating layer or conductor bar, acting as a stress relief mechanism
2Reliability
If two conductive layers with separating layer are used in conventional design, then delamination is prevented, but layer thickness increases
Solution Approach 1:
The patent uses a thin conductive fleece as the outer corona protection layer, which is flexible and conformable to the conductor bar surface, achieving reliable corona protection with minimal thickness increase
Solution Approach 2:
The external corona protection combines different materials (conductive layers, separating layer, conductive fleece) into a composite structure that achieves both delamination prevention and thin profile through optimized material selection and arrangement
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 effectively reduces layer thickness, ensures mechanical decoupling while maintaining electrical connection, and prevents damage from thermo-mechanical stresses, thereby enhancing the reliability and efficiency of the external corona protection.
Implementation Method 1
The two conductive layers are mechanically and electrically conductively connected to one another through recesses with the aid of a connection material having permanently elastic (in particular viscoelastic) properties
Implementation Method 2
Each of the two layers essentially consists of an electrically conductive, impregnable layer, which is each provided with a sliding layer
Data Source
Figure 1~2
AI summary
The invention relates to an external corona shielding (16) for a conductor rod (7) of an electrical machine (1), which conductor rod is coated with a main insulation layer (11). The external corona shielding (16) comprises a first layer (21) that covers the main insulation layer (11) and a second layer (20) that in turn covers the first layer (21). Each of the layers (20, 21) comprises a conductive, impregnable layer (22, 23) that is in each case provided with a sliding layer (25, 26), the sliding layers (25, 26) of the two layers (20, 21) facing each other. Each of the sliding layers (25, 26) also has at least one cut-out (30, 31), the two conductive layers (22, 23) being connected to each other through the said cut-outs (30, 31) by means of a permanently elastic, electrically conductive connection (32).