Miniature Circuit Breaker Shutter Terminal Safety
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Solution Overview
Problem
Existing methods for inserting and removing circuit breakers from electrical panels pose a risk of exposure to live parts, particularly in load centers, where deenergizing the panel is inconvenient and may not be feasible, especially in critical applications like data centers and hospitals.
Innovation Solution
A circuit breaker design with a box-shaped case and terminal arrangement that encloses connections, uses shutter assemblies and keying features to prevent access to live terminals during insertion and removal, and incorporates positive retention interlocks to ensure safe operation on energized panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If circuit breakers are mounted directly to the panelboard for easy installation and access, then ease of operation is improved, but the risk of exposure to live parts increases
Solution Approach 1:
A shutter assembly acts as an intermediary barrier between the operator and the live bus bars. The shutter is positioned in the circuit breaker compartment and can be opened only when a circuit breaker is properly inserted, allowing access to the bus bars only when necessary and safe.
Solution Approach 2:
The shutter assembly is designed to automatically open before the circuit breaker contacts the bus bars during insertion, and close before the circuit breaker is fully removed. This preliminary action ensures that the operator never exposes themselves to live parts unnecessarily.
2Object-affected harmful factors
If power is shut off to the panelboard to prevent contact with live conductors, then safety is improved, but availability of power source deteriorates
Solution Approach 1:
Instead of deenergizing the entire panelboard, the shutter assembly provides localized protection only in the specific circuit breaker compartment where work is being performed. Other circuits remain energized and available, maintaining system reliability while protecting the operator in the local work area.
3Ease of operation
If circuit breakers are designed with accessible terminals for wiring, then ease of operation is improved, but the risk of unintended contact with energized conductors increases
Solution Approach 1:
The terminal covers are designed to be dynamic - automatically opening when a circuit breaker is inserted into the compartment and closing when removed. This dynamic behavior ensures terminals are accessible only when the circuit breaker is properly installed and the shutter provides protection, eliminating unintended contact risks.
4Object-affected harmful factors
If shutter assemblies are added to prevent access to live terminals, then safety is improved, but device complexity increases
Solution Approach 1:
The shutter assembly is merged with the circuit breaker compartment structure, sharing common mounting points and integration with the bus bar support structure. This combining approach minimizes additional complexity by utilizing existing structural elements rather than adding completely separate components.
Data Source
AI summary
A miniature plug-on circuit breaker and complementary Load Center breaker compartment provide no exposed live touch points in the load center. The miniature circuit breaker has all terminals surrounded by its case. Line power and line side neutral terminals are accessed through the bottom of the circuit breaker. Load power and load side neutral terminals are accessed from an end panel of the circuit breaker. Load power and load side neutral terminals are covered such that they can only be wired when the circuit breaker is not in a breaker compartment of the complementary Load Center. Cover biasing features, or interference features, or both, can be provided so that an open load side terminal cover will have the cover closed upon insertion to the load center, and to prevent a closed load side terminal cover from being opened on an inserted circuit breaker.