ATH Arc Quenching Insert for Molded Case Circuit Breakers
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Solution Overview
Problem
There is a need for cost-effective molded case circuit breakers that meet UL® 489 requirements for overcurrent protection while minimizing maintenance and ensuring personal safety and proper dielectric clearances, as existing solutions fail to pass UL® 489 short-circuit testing for miniature and molded case circuit breakers.
Innovation Solution
The use of a three-dimensional rigid or semi-rigid arc quenching member made from alumina trihydrate (ATH) in a metal arc chute within a glass polyester molded circuit breaker case, which produces gases to quench arcs during short circuits, allowing the circuit breaker to interrupt current and meet UL®-489 guidelines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional arc extinguishing materials (melamine resin matrix with fibers) are used, then arc quenching capability is provided, but cost increases and manufacturing complexity increases
Solution Approach 1:
The patent changes the material composition parameters by using alumina trihydrate (ATH) as the primary arc-quenching compound instead of melamine resin matrix with fibers. This parameter change maintains arc quenching capability while simplifying the material composition and reducing manufacturing cost.
Solution Approach 2:
The patent employs a composite material structure where alumina trihydrate particles are embedded in a thermosetting resin matrix. This composite approach provides effective arc quenching through ATH decomposition while using a simple, cost-effective resin binder, avoiding the complexity of fiber-reinforced melamine composites.
2Reliability
If complex arc extinguishing structures are used, then arc quenching effectiveness is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies arc-quenching material (alumina trihydrate) locally on the arc chute surfaces where arcs are most likely to occur. This localized approach provides effective arc quenching exactly where needed without requiring complex structures throughout the entire arc chute assembly.
Solution Approach 2:
The patent uses a simple, cost-effective thermosetting resin matrix as the binder for alumina trihydrate particles. This simpler, less expensive material approach replaces complex fiber-reinforced structures while maintaining functional effectiveness for arc quenching.
3Ease of manufacture
If conventional arc chute materials are used, then manufacturing simplicity is maintained, but UL 489 short circuit testing requirements are not met
Solution Approach 1:
The patent changes the chemical composition parameters by using alumina trihydrate with specific particle size distributions and concentrations in the thermosetting resin matrix. This parameter optimization ensures UL 489 compliance while maintaining manufacturing simplicity through a straightforward composite material formulation.
Solution Approach 2:
The patent utilizes the phase transition properties of alumina trihydrate, which decomposes at elevated temperatures to release water vapor and form a protective atmosphere that quenches arcs. This phase transition mechanism provides reliable arc quenching for UL 489 compliance while keeping the material structure simple and manufacturable.
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 effectively quenches arcs during short circuit shots, enabling the circuit breaker to pass UL®-489 single pole short circuit testing and provide reliable protection, thus meeting the necessary construction and testing requirements.
Implementation Method 1
The arc-quenching of the ATH molded material can produce gases shown to quench an arc during successive short circuit shots
Implementation Method 2
In the event of an overcurrent condition (e.g., a short circuit), extremely high electromagnetic forces can be generated. The electromagnetic forces can be used to separate the movable contact from the stationary contact
Data Source
AI summary
Circuit interrupters such as breakers with a metal arc chute having a base and sidewalls extending outward from the base forming an open cavity, a movable arm holding a movable contact adjacent to the arc chute, a line conductor electrically connected to a stationary contact residing adjacent to the arc chute facing the movable contact and a three-dimensional molded arc quenching insert attached to the metal arc chute, and residing in the cavity of the metal arc chute between the stationary and movable contacts. The insert has an arc quenching material that optionally releases a gas such as hydrogen during an arcing event.