Circuit Breaker Truck Locking Structure for Switchgear Stability
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Solution Overview
Problem
Conventional switchgear systems fail to effectively restrain circuit breaker trucks during short circuit conditions, leading to potential arcing due to movement and separation of primary contacts from bushings.
Innovation Solution
A locking structure is integrated into the circuit breaker truck, utilizing a racking screw nut that floats linearly and is connected to a spring, allowing the truck to be locked into place by compressing the spring when the racking screw is rotated, engaging the locking structure with the frame's lock receiving openings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional wheel-rail engagement is used for truck movement, then ease of operation is improved, but reliability deteriorates under fault conditions due to inability to restrain twisting moments
Solution Approach 1:
The locking structure merges the movement function and restraint function into a single integrated mechanism. The locking structure includes a locking member that engages with the frame to restrain the truck, while simultaneously allowing controlled movement during normal operation. This combination resolves the contradiction by providing both ease of operation and reliability under fault conditions through a unified system.
Solution Approach 2:
The locking structure transitions from a static restraint system to a dynamic system that adapts to operational conditions. During normal operation, the locking member remains disengaged to allow free movement. Under fault conditions, the locking member automatically engages to restrain the truck. This dynamic behavior resolves the contradiction by providing the appropriate function based on the operational state.
2Reliability
If locking structure is added to restrain the truck, then reliability is improved, but device complexity increases
Solution Approach 1:
The locking structure is designed to perform multiple functions: it provides restraint under fault conditions, allows controlled movement during normal operation, and integrates with the existing wheel-rail engagement system. By making the locking structure multi-functional, the patent reduces the need for separate systems and minimizes overall device complexity while maintaining high reliability.
Solution Approach 2:
The locking structure is designed to automatically engage and disengage based on operational conditions without requiring external control systems. The locking member responds to the mechanical state of the truck and frame, providing self-regulating restraint. This self-service capability reduces complexity by eliminating the need for complex control mechanisms while ensuring reliable operation.
3Reliability
If the locking structure is always engaged, then reliability is improved, but ease of operation deteriorates due to restricted movement
Solution Approach 1:
The locking structure dynamically transitions between engaged and disengaged states based on operational requirements. During normal operation, the locking member is disengaged to allow free movement of the truck. Under fault conditions, the locking member automatically engages to provide stable restraint. This dynamic state transition resolves the contradiction by providing position stability only when needed while maintaining ease of operation during normal use.
Solution Approach 2:
The locking structure is designed to engage in advance of potential harmful movement under fault conditions. The locking member is positioned to automatically engage when the truck experiences twisting moments, preventing harmful displacement before it occurs. This preliminary anti-action ensures reliability without restricting normal operational movement.
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
The locking mechanism securely maintains the circuit breaker truck in position during short circuit events, preventing arcing and ensuring stability by overcoming twisting moments without additional operator intervention.
Implementation Method 1
A spring is provided between a portion of the truck and the racking screw nut such that during movement of the truck into the frame, rotation of the racking screw causes linear movement of the racking screw nut, with the racking screw nut pushing against the spring, with the spring pushing the truck to move the truck linearly.
Implementation Method 2
A racking screw; and a racking screw nut in threaded engagement with the racking screw. The racking screw nut is constructed and arranged to float linearly with respect to the truck.
Data Source
AI summary
A truck (12′) for mounting a circuit breaker (13) in a switchgear frame (14′) includes wheels (16), a racking screw (20), a nut (22) threaded with the racking screw. The nut floats linearly with respect to the truck. A spring (23) is provided between a portion of the truck and the nut such that during movement of the truck into the frame, rotation of the racking screw causes linear movement of the nut, with the nut pushing against the spring, with the spring pushing the truck to move the truck linearly. Locking structure is coupled with the such that when the truck is stopped and the racking screw continues to rotate, the nut will move to compress the spring, causing the locking structure to move from an unlocked position, disengaged with the frame, to a locked position, engaged with the frame.