Air Circuit Breaker Contacts with Inclined Surfaces
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Solution Overview
Problem
Air circuit breakers face challenges in maintaining stable contact between contacts due to strong electromagnetic repulsive forces generated by fault or abnormal currents, leading to potential separation and faults in lower circuits, especially when contact springs are overloaded to compensate.
Innovation Solution
The contacts are designed with inclined contact surfaces forming an acute angle, reducing the moment arm and thus the moment applied to the movable contact arm, allowing for stable contact maintenance even with smaller contact spring loads, and the acute angle is set between 10° to 40° to prevent excessive abrasion and separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact springs are overloaded to compensate for electromagnetic repulsive force, then contact stability is improved, but device complexity and wear increase
Solution Approach 1:
The patent changes the geometric parameters of the contact surfaces by introducing an inclination angle α (10° to 40°) relative to the vertical direction. This parameter change modifies the force distribution during contact, allowing the electromagnetic repulsive force to be partially converted into a stabilizing moment rather than a separating force, thereby reducing the burden on contact springs while maintaining contact stability.
Solution Approach 2:
The patent employs curved contact surfaces with specific inclination angles instead of flat vertical surfaces. The curved geometry creates a mechanical advantage where the electromagnetic repulsive force generates a stabilizing moment through the inclined surface, reducing the separating effect and allowing for lighter contact springs while maintaining reliable contact under fault conditions.
2Reliability
If contact surfaces are inclined to reduce moment arm, then contact stability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a practical range for the inclination angle α (10° to 40°) that balances the competing requirements of contact stability and manufacturing feasibility. This parameter range is optimized to provide sufficient stabilizing moment while remaining achievable with standard manufacturing tolerances, avoiding overly stringent precision requirements.
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 stabilizes the contact state between the fixed and movable contacts, reducing the impact of increased electromagnetic repulsive forces during fault or abnormal currents, while minimizing wear and maintaining durability by reducing the moment applied to the movable contact arm.
Implementation Method 1
an electromagnetic repulsive force is applied between the fixed contact 230 and the movable contact 350
Implementation Method 2
a contact spring 340 disposed between the movable contact arm 330 and the cage 320 to press the movable contact arm 330 toward the fixed contact arm 220
Data Source
AI summary
The present invention relates to a structure of contacts for an air circuit breaker, in which a movable contact arm can be stably brought into contact with a fixed contact arm by changing an applying direction of an electromagnetic repulsive force generated between a movable contact and a fixed contact, and, to this end, the structure, which includes the fixed contact arm having the fixed contact, and the movable contact arm having the movable contact and rotatably installed to be brought into contact with or separated from the fixed contact arm, is configured such that the fixed contact and the movable contact have contact surfaces, respectively, disposed in an inclined manner, and a line commonly passing the contact surfaces of the fixed contact and the movable contact forms an acute angle with respect to a line passing through a center of a longitudinal axis of the movable contact arm.