Cam Profile Push Link for Motor Protection Circuit Breaker
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Solution Overview
Problem
Conventional motor protection circuit breakers require high operating forces to switch between 'ON' and 'OFF' positions, and may fail to reliably break circuits due to incomplete latch release, leading to issues with circuit opening during abnormal currents.
Innovation Solution
A switching mechanism with a push link featuring a varying cam profile outer surface, which reduces the required operating force by allowing larger displacement of movable contact plates with smaller rotation angles, and enhances reliability through improved separation distances and automatic trip operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional push link with a fixed profile is used, then the structure is simple, but the operating force required is high and circuit breaking reliability is insufficient
Solution Approach 1:
The push link employs a dynamic cam profile instead of a fixed straight profile. The cam profile varies the transmission angle between the push link and cross bar during rotation, optimizing the mechanical advantage at different positions. This dynamic geometric transformation allows the system to overcome high contact pressure springs more easily while ensuring reliable circuit breaking.
Solution Approach 2:
The invention changes the geometric parameters of the push link by implementing a cam profile with varying radius of curvature. The cam profile includes a first portion with a first radius and a second portion with a second radius, allowing the transmission characteristics to change during operation. This parameter variation enables reduced operating force while maintaining sufficient contact pressure for reliable circuit breaking.
2Reliability
If the push link rotates through a large angle to separate contacts, then contact separation is reliable, but the operating force required increases
Solution Approach 1:
The cam profile on the push link dynamically adjusts the transmission angle during rotation. At the initial stage, the cam profile provides a larger transmission angle to reduce the force needed to start movement. As rotation progresses, the profile optimizes the angle to maintain sufficient contact pressure, enabling reliable separation with a smaller overall rotation angle and reduced operating effort.
Solution Approach 2:
The push link incorporates a cam profile with varying curvature radii. The first portion has a different radius of curvature than the second portion, creating an optimized rotational path. This curved profile transformation allows the system to achieve reliable contact separation while reducing the torque required during handle operation compared to a straight-line mechanism.
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 mechanism reduces the operational force needed to switch the circuit breaker while ensuring reliable circuit breaking, even during abnormal conditions, by enabling larger contact plate displacement with smaller rotations and maintaining contact separation distances.
Implementation Method 1
by elastic energy discharged from the trip spring, the push link connected to the trip spring is rotated
Implementation Method 2
a push link rotatable to a position to break the circuit by pressing the movable contact plates, and to a position not contacting the movable contact plates, having a part connected to the link mechanism and a part connected to the trip spring, and having an outer circumferential curved surface of a varying cam profile
Data Source
AI summary
A switch for a motor protection circuit breaker capable of reducing a force required to adjust a handle and capable of enhancing the reliability to break a circuit. The switch includes a push link having an outer circumferential curved surface of a varying cam profile, so as to enhance a function to break the circuit by pressing movable contact plates.