Segmented Fixed Contacts for Arc Extinction in Circuit Breakers
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Solution Overview
Problem
The existing medium and high-voltage switchgear and circuit breakers face significant damage due to the high-temperature switching arcs that occur during current interruption, leading to erosion and weakening of dielectric strength, despite the use of arcing contacts and arc-blowing techniques, which may not be feasible in all cases.
Innovation Solution
The solution involves designing fixed contacts with a main and auxiliary part, where both parts cross the sliding surface simultaneously or with a slight delay, allowing the switching arc to be shared between them, thereby reducing its duration and heat release, and ensuring simultaneous or almost simultaneous disconnection from the moving contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If arcing contacts are added to transfer current during opening, then damage to permanent contacts is reduced, but switching arcs still cause local melting and erosion
Solution Approach 1:
The fixed contacts are divided into two separate parts: main fixed contacts for normal current conduction and auxiliary fixed contacts for arc reception. This segmentation allows the switching arc to be directed to the auxiliary contacts while the main contacts remain protected, resolving the contradiction between reducing permanent contact damage and preventing switching arc damage.
Solution Approach 2:
The harmful switching arc function is extracted from the permanent fixed contacts and assigned to separate auxiliary fixed contacts. This extraction allows the permanent contacts to focus on their primary function of current conduction while the auxiliary contacts handle the arc, eliminating the trade-off between the two harmful effects.
2Object-affected harmful factors
If arc blowing techniques are applied to switching arcs, then arc damage is reduced, but equipment complexity increases and hermetic closure is required
Solution Approach 1:
The auxiliary fixed contacts are positioned and dimensioned to enable self-extinction of the switching arc through natural dielectric recovery, eliminating the need for complex arc blowing mechanisms, valves, or hermetic closure systems. The geometry and material properties of the auxiliary contacts themselves provide the arc-quenching function.
Solution Approach 2:
The arc-quenching function is extracted from complex mechanical or gaseous systems and embodied in the simple geometric and material design of the auxiliary fixed contacts, dramatically reducing device complexity while maintaining arc damage protection.
3Object-affected harmful factors
If the movable contact is divided into two parts with insulation, then switching arc damage is isolated, but the arc itself is not reduced and complexity increases
Solution Approach 1:
Instead of segmenting the movable contact, the fixed contacts are segmented into main and auxiliary parts. This segmentation achieves arc isolation and damage reduction while maintaining a simpler overall structure, as the stationary contacts are easier to design and position than moving parts.
Solution Approach 2:
Rather than modifying the movable contact to control the arc, the invention inverts the approach by using the fixed contacts' geometry and positioning to naturally guide and extinguish the arc, achieving the same protective effect with simpler means.
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 significantly reduces the damage to the switchgear by hastening the extinction of switching arcs, minimizing heat release and contact erosion, while maintaining the arc's isolation to reduce overall damage.
Implementation Method 1
an electric arc then forms between the moving contact and the insulated fixed contact
Implementation Method 2
compressed in a chamber by the moving contact stroke and then released by the opening of a valve
Data Source
Figure 1~4
Figure 5~7
Figure 8~9
AI summary
High- or medium-voltage circuit breaker, where a movable contact (1) is displaced by sliding, so as to clear fixed contacts (11, 12) of its gliding surface (2). In accordance with the invention, the fixed contacts (11, 12) possess switching parts (9) separated almost simultaneously, by virtue of an additional difference in level (19) of the movable contact (1), so as to cause the appearance of two simultaneous switching arcs (14, 15), which are extinguished much more quickly than a single, before the current is communicated to the customary arc contacts (5). By this arrangement the fixed contacts (11, 12) and their environment are less exposed to damage.