Movable Contact Assembly With Floating Arms and Reduced Shunt Deflection
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Solution Overview
Problem
Existing electrical switching apparatus, such as circuit breakers, face issues with shunts that do not fit well within limited spacings, causing interference and flexibility problems due to expansion and bunching during short circuit events, and clinch joint assemblies that have limited torque balance control and are restricted to a two-contact arm configuration.
Innovation Solution
A movable contact assembly with a carriage assembly, isolation members, and a reduced-length shunt configuration that minimizes deflection and friction, allowing multiple contact arms to float on an axle with controlled friction, eliminating the need for shunts and enhancing torque balance control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire rope or braided-type shunts are used, then electrical connection is provided, but they expand outward and interfere with adjacent structures, and bunch together during short circuit events inhibiting flexibility
Solution Approach 1:
The shunt is divided into multiple discrete contact arms (first contact arm, second contact arm, third contact arm, fourth contact arm) that can move independently on the axle assembly. Each contact arm is electrically connected through the axle rather than using continuous wire ropes, allowing individual movement without bunching while maintaining electrical connectivity.
Solution Approach 2:
The contact arms are designed to be rotatable on the axle assembly, providing dynamic movement capability. The friction control mechanism allows the contact arms to float and move freely under normal conditions while maintaining electrical connection, and can be controlled to provide specific friction during fault conditions.
2Ease of operation
If elongated shunts are used in S-shape configuration, then movement of contact finger is accommodated, but magnetic fields during overcurrent events cause rapid shape change and extreme compound deflection
Solution Approach 1:
Instead of using a single elongated S-shaped shunt, the electrical connection is segmented into multiple discrete contact arms connected through the axle assembly. This eliminates the long continuous shunt that would be susceptible to magnetic field-induced deflection, while still accommodating contact finger movement through the rotatable design.
Solution Approach 2:
The axle assembly acts as an intermediary element that provides both mechanical support and electrical connection between the contact arms and the conductor assembly. It mediates the movement requirements while maintaining electrical connectivity, replacing the function of the elongated shunt without the associated magnetic field problems.
3Manufacturing precision
If clinch joint assembly is used, then torque balance control is provided, but it is restricted to two-contact arm configuration
Solution Approach 1:
The axle assembly serves multiple functions: it provides mechanical rotation support for contact arms, maintains electrical connection between all contact arms and the conductor assembly, and enables torque balance control through friction management. This universal design supports any number of contact arms (at least three according to the claims) rather than being limited to two.
Solution Approach 2:
The patent transitions from a planar two-contact arm configuration to a three-dimensional arrangement with multiple contact arms (at least three) positioned around the axle assembly. This dimensional expansion allows for more versatile electrical switching configurations while maintaining torque balance control through the friction management mechanism.
4Reliability
If shunts are used to electrically connect movable contact assembly to conductor assembly, then electrical connection is provided, but they create friction and wear during operation
Solution Approach 1:
The patent replaces the traditional mechanical shunt system with an axle assembly that combines mechanical rotation support with electrical connection. The contact arms rotate on the axle rather than sliding against shunts, reducing friction and wear. The electrical connection is maintained through the axial connection rather than through sliding contact with shunts.
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 improves the size and performance of circuit breakers by reducing deflection, controlling friction, and allowing multiple contact arms, enabling better handling of overcurrent events with enhanced opening characteristics and reduced wear.
Implementation Method 1
Each contact arm is floatably coupled to the axle assembly with a controlled amount of friction
Implementation Method 2
elongated shunts create magnetic fields during an overcurrent event. Such magnetic fields from adjacent shunts, as well as the movement caused by the operating mechanism, cause the shunt to rapidly change shape
Data Source
Figure 1
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Figure 4
AI summary
A movable contact assembly (50) for an electrical switching apparatus (10) is provided. The movable contact assembly (50) includes a number of shunts (54), and, a carriage assembly (52) including two sidewalls (70,74) and a contact arm assembly (65 ). The carriage assembly sidewalls (70,74) are disposed in a spaced relation. The contact arm assembly (65 ) includes a plurality of contact arms (58 A, 58B, 58C, 58D), a number of isolation members (56 A, 56B), a number of movable contacts (60), and an axle (62). Each contact arm (58) defines an opening. One movable contact (50) is disposed on each contact arm (58). Each contact arm (58) is rotatably coupled to the axle (62) with the axle (62) extending through the contact arm (58) opening. Each isolation member (56 A, 56B) is disposed adjacent at least one contact arm (58). Each isolation member (56 A, 56B) is coupled to, and in electrical communication with the adjacent contact arm (58 A, 58B, 58C, 58D). The shunts (54) are coupled to, and in electrical communication with, the isolation members (56A, 56B). In this configuration, no shunt (54) operatively engages a contact arm (65).