Miniature Circuit Breaker Trip Assembly Magnetic Gap Control
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Solution Overview
Problem
Existing circuit breakers experience inconsistent tripping due to variances in magnetic gap between the armature and yoke caused by component tolerances, affecting tripping sensitivity and timing, especially in overcurrent conditions.
Innovation Solution
A trip assembly design that maintains a consistent magnetic gap between the yoke and armature by localizing components within a small area, using a trip lever with specific surfaces and a yoke tab to control the magnetic gap, allowing for smaller tolerances and predictable tripping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the magnetic gap is made smaller to improve tripping sensitivity, then the tripping response to overcurrent conditions improves, but the consistency of the magnetic gap becomes more sensitive to component tolerances
Solution Approach 1:
The patent applies local quality by concentrating the magnetic gap control in a specific localized area rather than distributing it across multiple components. The magnetic gap is formed between the armature and yoke in a confined space, allowing precise control of the gap dimension at this critical location while other components can have standard tolerances. This localized approach maintains small, consistent gap dimensions for sensitive tripping while reducing the propagation of tolerance variations from multiple parts.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the geometric parameters of the armature and yoke components. Specifically, the armature includes a face with a specific area and the yoke has a corresponding surface, with their relative positioning and dimensions carefully designed to maintain a consistent magnetic gap. By adjusting these geometric parameters, the patent achieves both small gap dimensions for sensitivity and consistent gap dimensions for reliability.
2Adaptability or versatility
If multiple parts are used to form the magnetic gap, then the assembly flexibility improves, but the manufacturing precision of the magnetic gap decreases due to tolerance accumulation
Solution Approach 1:
The patent applies merging by integrating the magnetic gap formation into a single assembly operation rather than requiring multiple adjusted components. The armature and yoke are designed to form the magnetic gap when brought together in the assembled circuit breaker, with the gap dimension determined by the overall assembly geometry rather than by stacking multiple precision-spaced parts. This reduces tolerance accumulation while maintaining assembly flexibility.
Solution Approach 2:
The patent uses segmentation by dividing the trip actuator into distinct functional components (armature, yoke, bimetallic strip) that can be manufactured separately with standard tolerances, then assembled to form the magnetic gap. The segmentation allows each component to be optimized for its specific function while the overall assembly geometry controls the magnetic gap dimension, reducing the impact of individual component tolerances.
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
Ensures consistent and predictable tripping levels by maintaining a precise magnetic gap, enhancing the reliability of overcurrent protection in circuit breakers.
Implementation Method 1
the bimetallic member generates a magnetic field which, in turn, generates a magnetic flux in the armature and the yoke
Implementation Method 2
generates a magnetic flux in the armature and the yoke that are separated by a magnetic gap
Implementation Method 3
The magnetic flux causes the armature to move toward the yoke, thereby unlatching the trip lever from the armature into the tripped position
Data Source
AI summary
A trip assembly for a circuit breaker includes a trip lever and a trip actuator. The trip lever causes electrical contacts, which are in a closed position, to disengage from each other into an open position and interrupt current flow to a circuit, when tripped by the trip actuator due to an overcurrent condition. The trip actuator includes a bimetallic member, a yoke and an armature with an opening in which an end of the trip lever is latched in the closed position. The yoke includes a tab adjacent to the opening. When the trip lever is latched in the opening, the end of the trip lever includes first, second and third surfaces that contact a front surface of the armature, an interior surface of the armature defining the opening, and the tab of the yoke, respectively, to provide a consistent magnetic gap between the back side of the armature and the yoke.