Ferromagnetic Shield Circuit Breaker Contact Force
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Solution Overview
Problem
Molded case electric circuit breakers have a low upper limit for ensuring proper contact between fixed and movable pads, failing to resist high overcurrents due to repulsive electrodynamic forces, and existing solutions either increase mechanical force requirements or enlarge the circuit breaker, making them inadequate for modern selectivity requirements.
Innovation Solution
The design incorporates a first and second contact carrying support with movable portions and electromagnetic shielding, using helical compression springs and ferromagnetic shields to maintain contact pressure without increasing the actuation force, allowing higher current thresholds while maintaining compact size and cost efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compression springs are strengthened to increase contact force between pads, then the current threshold for maintaining contact is improved, but the actuation force required by the mechanism increases beyond acceptable limits
Solution Approach 1:
A ferromagnetic shield is introduced as an intermediary component between the movable and fixed pads. This shield redirects the electromagnetic repulsive forces generated during overcurrent events away from the contact pads, allowing the compression springs to maintain contact force without requiring excessive actuation force. The shield acts as a mediator that manages the force distribution in the system.
Solution Approach 2:
The invention changes the magnetic properties parameter by introducing ferromagnetic material (the shield) into the system. This material has high magnetic permeability that allows it to redirect electromagnetic flux and repulsive forces, fundamentally altering how forces are distributed in the contact assembly without changing the mechanical spring characteristics or actuation mechanism.
2Reliability
If multiple supporting elements are used to increase the number of contact surfaces, then the current threshold is improved, but the device size and complexity increase
Solution Approach 1:
The ferromagnetic shield serves as a single intermediary component that provides the functionality previously requiring multiple supporting elements. By redirecting electromagnetic forces at the source, the shield eliminates the need for parallel contact paths through multiple supporting elements, thereby reducing structural complexity while maintaining or improving current resistance capability.
3Reliability
If multiple supporting elements are used to distribute current, then the current threshold is improved, but the circuit breaker size increases
Solution Approach 1:
The introduction of ferromagnetic material changes the electromagnetic field distribution parameter within the circuit breaker. This allows the existing compact structure to handle higher currents by redirecting electromagnetic forces through the shield, rather than requiring a larger physical structure with multiple supporting elements to distribute the current load.
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
This configuration effectively raises the current threshold for maintaining contact between pads to 40 kA or beyond, meeting modern selectivity requirements with a smaller and less costly circuit breaker, ensuring service continuity and reducing installation complexity.
Implementation Method 1
the use of a ferromagnetic shield, which is interposed between a movable pad and a fixed pad, and which is adapted to redirect electromagnetic repulsive forces away from one another
Implementation Method 2
suitable compression springs provided between the contact carrying shaft and the supporting elements of movable pads
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A high performance circuit breaker wherein an electric current flows through the first (22) and second (32) contact carrying support. The terminal (24) is crossed by electric current (I1) in a set orientation, whereas the arms (28) are crossed by electric current (I2) having a substantially opposed orientation in an essentially parallel direction, with respect to current (h). The interaction between the currents (I1 2) generate a repulsive electromagnetic force F which is able to distance the arms from the terminal, creating additional contact pressure between the contacts. Even though the second contact carrying support is crossed by electric current (b) having a substantially opposed orientation in an essentially parallel direction with respect to current (I2), generation of a further electromagnetic force, which would tend to separate the arms from the second contact carrying support, unwanted electromagnetic repulsion between the contacts is avoided by the first (50) and second (70) ferromagnetic shield.