Circuit Breaker Current Limiter With Guided Movable Bar Rotation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current limiting devices in molded case circuit breakers (MCCBs) experience degradation in performance due to asymmetrical contact repulsion forces between movable and fixed contacts during fault currents, leading to inconsistent breaking operations, especially when dealing with small currents.
Innovation Solution
A current limiting device with a shaft and movable bar featuring a movable bar guide portion that protrudes towards the shaft and a cam part on the movable bar to limit the rotation center movement, ensuring that only the side with a strong contact repulsion force moves past the dead point while the side with a weak force does not, thereby maintaining proper separation and preventing performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a double rotating contact structure is used to improve current limiting characteristics, then the breaking capacity is improved, but the performance degrades due to asymmetrical contact repulsion forces
Solution Approach 1:
The patent applies asymmetry by designing the movable bar guide portion with a specific geometric configuration that intentionally creates asymmetrical guidance. The guide portion has a first guide surface and a second guide surface with different orientations, allowing the movable bar to rotate asymmetrically about the shaft center axis. This asymmetrical design compensates for the asymmetrical contact repulsion forces, ensuring stable and reliable current limiting performance even when the contact forces are unequal.
2Speed
If the movable bar is allowed to rotate freely to pass the dead point quickly, then the separation speed is improved, but the rotation center moves inconsistently due to asymmetrical forces
Solution Approach 1:
The patent introduces the movable bar guide portion as an intermediary element between the movable bar and the shaft. This guide portion mediates the rotation of the movable bar by providing controlled guidance through its first and second guide surfaces. The guide surfaces constrain the rotation path, ensuring that the movable bar passes through the dead point consistently while maintaining accurate rotation center position, thus resolving the conflict between speed and precision.
3Force
If elastic members are used to provide repulsion force, then the contact separation is improved, but asymmetrical forces cause inconsistent movement of the movable bar
Solution Approach 1:
The patent applies asymmetry by designing the movable bar guide portion with a specific geometric configuration that intentionally creates asymmetrical guidance. The guide portion has a first guide surface and a second guide surface with different orientations, allowing the movable bar to rotate asymmetrically about the shaft center axis. This asymmetrical design compensates for the asymmetrical contact repulsion forces, ensuring stable and reliable current limiting performance even when the contact forces are unequal.
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 solution minimizes the movement of the rotation center, ensures complete separation of contacts, and shortens the time to reach the predetermined opening position, allowing for quick arc breaking and maintaining high breaking performance.
Implementation Method 1
a shaft 13 having an elastic member 17 on an inner side... the movable bar 15 is positioned in a position spaced apart from the fixed bar 11 upon receiving elastic force from the elastic member 17
Implementation Method 2
when a fault current occurs in the MCCB, a contact repulsion force is generated between a fixed contact and a movable contact... due to the contact repulsive force, a movable bar having a movable contact moves at a fast speed
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
In present disclosure, a movable bar guide portion (133) is formed to protrude toward a movable bar in a shaft having a movable bar (120), and when a fault current is applied and the movable bar is rotated due to electromagnetic repulsion force, the movable bar and the movable bar guide portion contact each other, and thus, when the movable bar is rotated through the movable guide portion, movement of a rotation center of the movable bar is minimized.