Arc Chute Rear Venting Layout to Prevent Arc Reformation
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Solution Overview
Problem
Existing arc extinguishing devices in miniature circuit breakers face inefficiencies in preventing the reformation of electric arcs behind the arc chute, leading to potential device damage and safety risks due to ionized air recombination.
Innovation Solution
An insulating rear plate with separate vertical portions and exhaust zones, each with vents facing spaces between arc splitter plates, is fixed at the back of the arc chute to redirect and recirculate exhaust air, preventing arc reformation by separating the air flow and minimizing ionized air escape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single exhaust opening is used at the rear of the arc splitter stack, then the structure is simple, but ionized air escapes and causes arc reformation behind the chute
Solution Approach 1:
The exhaust opening is segmented into multiple separate openings (first exhaust opening and second exhaust opening) positioned at different locations on the rear plate. This segmentation prevents ionized air from escaping in a single uncontrolled path, thereby preventing arc reformation while maintaining structural simplicity through the use of multiple basic opening elements.
2Productivity
If exhaust openings are positioned to maximize ionized air evacuation, then arc cooling is improved, but ionized air may escape and reform arcs externally
Solution Approach 1:
Different regions of the rear plate are assigned different functions through locally differentiated opening configurations. The first exhaust opening is positioned to evacuate ionized air from the upper region while the second exhaust opening handles the lower region, ensuring that ionized air is channeled in controlled directions that prevent external arc formation while maintaining efficient evacuation.
3Reliability
If the rear plate is made solid to prevent arc reformation, then arc safety is improved, but ionized air cannot escape and accumulates behind the chute
Solution Approach 1:
The rear plate is designed with a porous structure in the form of strategically positioned exhaust openings rather than being completely solid. This allows ionized air to escape through controlled pores (openings) while the overall plate structure remains intact to prevent arc reformation, balancing safety requirements with the need for ionized air evacuation.
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
Effectively prevents electric arc reformation behind the arc splitter stack, enhancing the arc extinguishing process and reducing external ignition risks by redirecting and recirculating ionized air within the miniature circuit breaker.
Implementation Method 1
Circuit breakers contain so-called arc chutes, a stack of mutually insulated parallel metal plates that divide and cool the arc, thus permitting the cooling and evacuation of the ionized air. By splitting the arc into smaller arcs, the arc is cooled down while the arc voltage is increased and serves as an additional impedance that limits the current through the circuit breaker.
Implementation Method 2
Ionized air is evacuated through the arc chute and may then exit the miniature circuit breaker through ventilation openings (or exhaust vents). The insulating rear plate being subdivided into a first and a second vertical portions, each vertical portion comprising respectively a first and a second exhaust zone, each exhaust zone comprising one or more vents facing spaces between two adjacent extinguishing splitter plates
Data Source
AI summary
An arc extinguishing device for a circuit-breaker, including an arc splitter stack. The arc splitter stack including a plurality of extinguishing splitter plates stacked on top of each other and being kept apart from each other in the direction of stacking. The arc extinguishing device including an insulating rear plate being fixed at the back of the arc splitter stack, the insulation rear plate being subdivided into a first and a second vertical portions, each vertical portion including respectively a first and a second exhaust zone, each exhaust zone including one or more vents facing spaces between two adjacent extinguishing splitter plates, the first exhaust zone being located in an upper part of the first portion, the second exhaust zone being located in a lower part of the second portion.