Contact Finger Segmentation for High Voltage Switching Robustness
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Solution Overview
Problem
High voltage electrical switching devices face damage from electromagnetic forces during current commutation, as not all contact fingers separate simultaneously, leading to deformation and reduced robustness.
Innovation Solution
The electrical switching device features a nominal contact arrangement with a finger cage and grouped contact fingers, where the contact fingers are separated by varying lengths of empty slots to increase circumferential stiffness and reduce radial stiffness, allowing for even contact separation and minimizing deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If contact fingers are separated by empty slots to reduce radial stiffness and allow force fit closure, then the contact fingers gain necessary elasticity for closing and tolerance compensation, but the circumferential stiffness is reduced leading to contact finger deformation under electromagnetic forces
Solution Approach 1:
The empty slots are segmented into two types: first empty slots extending fully to the free end of contact fingers to provide radial elasticity for closing, and second empty slots that are shorter and do not extend to the free end to maintain circumferential stiffness. This segmentation allows different portions of the same structural feature to serve different functional purposes.
Solution Approach 2:
Different regions of the contact finger structure are given different properties: the regions near the base have full empty slots for radial flexibility, while the regions toward the free end have shorter empty slots for circumferential rigidity. This local differentiation of structural properties optimizes both closing elasticity and operational strength.
2Reliability
If all contact fingers separate simultaneously from the mating nominal contact, then the current commutation is smooth and uniform, but the electromagnetic forces cause adjacent fingers to be attracted towards one another and bend in non-radial direction
Solution Approach 1:
The second empty slots are made asymmetrically shorter than the first empty slots, creating an asymmetric stiffness distribution that provides circumferential support to prevent non-radial bending while maintaining the symmetry needed for uniform current distribution during commutation.
3Strength
If the contact fingers are made more rigid to prevent deformation under electromagnetic forces, then the contact fingers maintain their shape better, but the ability to compensate for manufacturing tolerances and achieve force fit closure is reduced
Solution Approach 1:
The empty slot structure is segmented into first and second slots with different lengths, creating zones of different stiffness. The first full-length slots provide tolerance compensation and force fit capability, while the second shorter slots provide deformation resistance, achieving both requirements through structural segmentation.
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 enhances the robustness of high voltage switching devices by reducing contact finger deformation and ensuring even contact separation, thereby preventing damage from electromagnetic forces.
Implementation Method 1
significant electromagnetic forces act on these contact fingers and can deform them permanently. The deformation manifests itself in that adjacent fingers are attracted towards one another as a result of the Lorentz-force
Data Source
AI summary
An electrical switching device for medium or high voltage circuits having at least a nominal contact arrangement, wherein the nominal contact arrangement includes at least a first nominal contact including a plurality of contact fingers forming a finger cage concentric with respect to a longitudinal axis, wherein the contact fingers are separated from one another by empty slots extending up to a free end of the contact fingers. The empty slots include first and second empty slots, wherein the second empty slots are shorter than the first empty slots, and wherein the contact fingers are grouped in groups, with the contact fingers of each group being separated by second empty slots and the contact fingers of adjacent groups being separated by first empty slots.