Bi-directional Thermal Calibration of Circuit Breaker Frame
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Solution Overview
Problem
Current methods for thermally calibrating circuit interrupters are limited in their ability to adjust and re-calibrate thermal trip assemblies to achieve specific thermal responses, leading to inconsistencies and potential failures in meeting desired calibration ranges.
Innovation Solution
A bi-directional adjustment method using a deformable frame with an elongated slot and a forked calibration tool to calibrate and re-calibrate the thermal trip assembly, allowing for different thermal responses by rotating the tool in specific directions to deform the frame and adjust the bimetal assembly's angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a flat bit is used to deform the frame in a single direction during thermal calibration, then the thermal trip time can be reduced to meet minimum time limits, but the circuit breaker cannot be re-calibrated if it trips too quickly (below minimum limits)
Solution Approach 1:
The patent applies inversion by enabling bidirectional frame deformation. The elongated slot allows the calibration tool to deform the frame in opposite directions: clockwise rotation reduces thermal trip time (for breakers tripping too slowly), while counterclockwise rotation increases thermal trip time (for breakers tripping too quickly). This resolves the limitation of unidirectional calibration tools that could only adjust in one direction.
Solution Approach 2:
The patent implements dynamics by making the frame deformation adjustable and reversible. The elongated slot design allows dynamic adjustment of the frame's deformable portion, enabling operators to rotate the calibration tool in either direction to achieve the desired thermal calibration. This dynamic capability allows the same tool and frame to adapt to different calibration needs, providing versatility in adjusting thermal trip characteristics.
2Ease of manufacture
If the frame is designed with fixed geometry, then manufacturing is simpler, but thermal calibration cannot adjust the bimetal starting angle to achieve desired thermal responses
Solution Approach 1:
The patent applies segmentation by dividing the frame into distinct functional portions: a fixed portion providing structural stability and a deformable portion with an elongated slot that allows calibration adjustment. This segmentation enables the frame to maintain overall structural integrity while providing a specific region that can be deformed during thermal calibration to adjust the bimetal starting angle and achieve desired thermal responses.
Solution Approach 2:
The patent implements local quality by creating a localized deformable region in the frame through the elongated slot. Only the specific portion of the frame adjacent to the slot is designed to be deformable, while the rest of the frame maintains its fixed geometry. This allows thermal calibration to locally adjust the bimetal assembly angle without requiring changes to the entire frame structure, maintaining manufacturing simplicity while enabling calibration precision.
3Speed
If circuit breakers are calibrated to trip quickly, then protection response is faster, but breakers may trip unnecessarily (fall out of calibration range below minimum limits)
Solution Approach 1:
The patent implements feedback by enabling bidirectional calibration adjustment. After initial thermal calibration, test results provide feedback on whether the circuit breaker trips within the desired time range. If the breaker trips too quickly (below minimum limits), the feedback mechanism allows operators to use the elongated slot to deform the frame in the counterclockwise direction, increasing the thermal trip time and bringing the breaker back into the acceptable calibration range. This feedback loop ensures calibration range consistency while maintaining fast protection response.
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 approach enables precise calibration and re-calibration of thermal trip assemblies, ensuring circuit breakers trip at appropriate temperatures, reducing scrap and rework by maintaining or adjusting thermal calibration within desired limits.
Implementation Method 1
rotating the tool in a first rotational direction and responsively deforming the elongated deformable portion and moving the movable portion of the deformable frame in a first direction
Data Source
AI summary
A circuit breaker test system includes a circuit breaker under test having a deformable frame with an elongated slot, an elongated deformable portion adjacent the elongated slot and a movable portion adjacent the deformable portion, and a thermal trip assembly coupled to the movable portion. A calibration device includes a forked tool straddling the deformable portion. The trip assembly has a first thermal response. The calibration device rotates the tool in a first rotational direction and responsively deforms the deformable portion and moves the movable portion in a first direction, in order to calibrate the trip assembly for a second different thermal response. The calibration device rotates the tool in an opposite second rotational direction and responsively deforms the deformable portion and moves the movable portion in an opposite second direction, in order to re-calibrate the trip assembly for a third thermal response between the first and second thermal responses.