Medium Voltage Circuit Breaker Arc Chute Design
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Solution Overview
Problem
Existing medium voltage circuit breakers face issues with horn wear-out and gas generation due to arc heating, leading to frequent replacements and potential re-ignition risks, especially in high-speed DC circuits used in railway vehicles.
Innovation Solution
A switch unit with an arc chute comprising two stacks of parallel metal plates, where the switch contacts are connected to the most proximal metal plates, allowing arc feet to jump and extinguish on these plates, reducing horn heating and facilitating easier maintenance by extending the lifetime of the horns and arc chute.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If horns are used to guide arcs in known circuit breakers, then arc guidance function is achieved, but horn wear-out occurs due to arc heating and evaporation
Solution Approach 1:
The invention extracts the arc-conducting function from the horns and transfers it to the arc chute with metal plates. The horns now only guide the arc, while the metal plates in the arc chute conduct the arc feet, preventing direct arc contact with horns and eliminating horn evaporation and gas generation.
Solution Approach 2:
The metal plates in the arc chute serve as an intermediary between the horns and the arc feet. The arc feet jump from the horns to the metal plates, and the plates conduct the arc current away from the horns, preventing horn degradation while maintaining arc guidance and extinction functions.
2Reliability
If horns are exchanged regularly in known circuit breakers, then reliability is maintained, but maintenance complexity increases
Solution Approach 1:
The invention removes the arc-conducting function from the horns, which were previously subject to wear and required regular replacement. By transferring this function to the arc chute's metal plates, the horns become durable guide elements that do not require frequent maintenance.
Solution Approach 2:
The invention makes the arc chute with metal plates the replaceable component instead of the horns. The arc chute is designed to be more easily replaceable than the horns, simplifying maintenance while the horns become long-lasting components that remain in the circuit breaker for its entire service life.
3Reliability
If arc feet remain on horns during arcing time, then arc guidance is achieved, but heat concentration occurs leading to plasma generation and re-ignition risk
Solution Approach 1:
The invention extracts the arc feet from the horns during the arcing process. The arc feet are made to jump to the metal plates in the arc chute, which then conduct the arc current away from the horns, preventing heat concentration and plasma generation at the horn locations.
Solution Approach 2:
The metal plates act as an intermediary that receives the arc feet from the horns and conducts the arc current through a longer path in the arc chute. This intermediary function dissipates the arc energy over a larger volume, preventing the localized heat concentration that causes plasma generation and re-ignition.
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
The solution reduces horn wear, minimizes gas generation near switch contacts, and allows for longer maintenance intervals by transferring arc feet efficiently to the arc chute, thereby enhancing the reliability and safety of medium voltage circuit breakers.
Implementation Method 1
the feet of the arcs remain on the horns during the arcing time... the arc heats up the horns... the arc chute comprises at least two stacks of a plurality of substantially parallel metal plates
Data Source
AI summary
A switch unit 200 for a voltage circuit breaker that includes a first switch contact 202a and a second switch contact 202b. The first switch contact 202a is movable between a first position in which the first switch contact 202a contacts the second switch contact and a second position in which the first and second switch contacts 202a, 202b are separated from each other. Further, a positioning element to position an arc chute 100 on the switch unit. The arc chute 100 includes at least two stacks 102, 106 of a plurality of substantially parallel metal plates 104, 104a, 104b, . . . , 104n, 108, 108a, 108b, . . . , 108n. The switch unit includes a first connection device 120, 230a capable to electrically connect the first switch contact 202a to a predetermined metal plate 104a selected of the most proximal 25% metal plates of the first stack 102. A second connection device 122a 122b, 230b capable to electrically connect the second switch contact to a predetermined metal plate 108a selected of the most proximal 25% metal plates of the second stack 106.