Multi-Finger Electrical Contact Assemblies with Unequal Resistance
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Solution Overview
Problem
Conventional circuit breakers face limitations in high current withstand capabilities due to magnetic blow-apart forces and heat generation at contact interfaces, particularly in AC applications where eddy current effects lead to asymmetrical current distribution, making outer fingers more vulnerable to damage.
Innovation Solution
A multi-finger electrical contact assembly is designed with at least two outer fingers and one inner finger, where the electrical resistance between the second end of an electrical conductor and the moveable contact of the outer finger is greater than that between the second end of the conductor and the moveable contact of the inner finger, balancing current flow and reducing the risk of damage by increasing resistance in the outer paths relative to inner paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional circuit breakers use multi-finger electrical contact assemblies with equal electrical resistance in all fingers, then the structure is simple and easy to manufacture, but the current distribution becomes asymmetrical causing outer fingers to experience higher current density leading to magnetic blow-apart forces and overheating
Solution Approach 1:
The patent applies local quality by assigning different electrical resistance values to different fingers based on their position. Outer fingers are given higher electrical resistance than inner fingers to compensate for the asymmetrical current distribution caused by eddy current effects. This localized modification of electrical resistance properties ensures that current density is balanced across all fingers, preventing overheating and magnetic blow-apart forces in outer fingers while maintaining overall system reliability.
2Temperature
If outer fingers are designed with higher electrical resistance to balance current distribution, then current density becomes more uniform across all fingers, but the electrical resistance configuration becomes more complex
Solution Approach 1:
The patent applies parameter changes by modifying the electrical resistance parameter of outer fingers relative to inner fingers. Specifically, outer fingers are designed with higher electrical resistance to reduce current density and consequently lower the temperature at contact interfaces. This parameter adjustment directly addresses the overheating issue in outer fingers caused by asymmetrical current distribution during AC operation.
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 enhances the current withstand capabilities of circuit breakers by distributing current more evenly across fingers, reducing the risk of magnetic blow-apart and overheating, thereby increasing the devices' current withstand ratings without physical damage to the contacts.
Implementation Method 1
an electrical resistance between a second end of an electrical conductor coupled to an outer finger and a moveable contact of the outer finger is greater than an electrical resistance between the second end of an electrical conductor coupled to the at least one inner finger and a moveable contact of the at least one inner finger
Data Source
AI summary
A multi-finger electrical contact assembly having unequal electrical resistance in current paths through each finger providing relatively high current withstand capability. The multi-finger electrical contact assembly includes three or more fingers each with a coupled conductor, wherein one or more outer fingers and coupled conductor of the assembly have greater electrical resistance than an inner finger and coupled conductor. Multi-phase circuit breakers including the multi-finger electrical contact assembly and methods are provided, as are other aspects.