Compliant Interface Lever for Circuit Breaker Undervoltage Relay Reset
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Solution Overview
Problem
Existing undervoltage release mechanisms in circuit breakers face issues with overtravel and tolerance stackup, leading to excessive stress on components and compromised functionality.
Innovation Solution
An interface lever made of compliant material is introduced to couple the handle arm pin with the reset lever, accommodating overtravel and tolerance stackup by translating arcuate movement into actuation of the reset lever, ensuring reliable resetting of the undervoltage relay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a rigid pin directly contacts the reset lever, then the mechanism is simple, but excessive stress occurs on the undervoltage relay due to overtravel and tolerance stackup
Solution Approach 1:
A compliant interface lever is introduced as an intermediary component between the handle arm pin and the reset lever. This interface lever absorbs overtravel and tolerance stackup through its compliant material, preventing excessive stress from being transmitted to the undervoltage relay while maintaining the simplicity of the overall mechanism.
Solution Approach 2:
The interface lever is made of compliant material that changes its mechanical properties to accommodate overtravel. The compliant material allows the lever to flex and deform elastically, absorbing the excess movement without transmitting harmful forces to the undervoltage relay, thus resolving the contradiction between mechanism simplicity and relay reliability.
2Device complexity
If the handle arm pin directly actuates the reset lever, then the structure is compact, but tolerance stackup causes excessive stress on components
Solution Approach 1:
The compliant interface lever serves as a mediator between the handle arm pin and the reset lever. It maintains the compact structure while introducing a compliant element that absorbs tolerance stackup, thereby preventing excessive stress from being transmitted through the direct connection.
3Ease of operation
If the handle arm moves beyond the off position to reset the mechanism, then the reset function is achieved, but overtravel causes stress on the undervoltage relay
Solution Approach 1:
The compliant interface lever provides beforehand cushioning by absorbing the overtravel that occurs when the handle arm moves beyond the off position. The compliant material acts as a cushion that prevents the full force of overtravel from being transmitted to the undervoltage relay, protecting it from excessive stress while allowing the reset function to be performed.
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 compliant interface lever effectively reduces stress on the undervoltage relay by flexing to accommodate overtravel and tolerance variations, ensuring reliable operation and extending the lifespan of the mechanism.
Implementation Method 1
an interface lever between the handle arm pin and the reset lever, the interface lever structured to translate arcuate movement of the handle arm pin as the handle arm moves to the off position into actuation of the reset lever, the interface lever being formed at least partially of a compliant material that flexes to accommodate for overtravel of the handle arm pin and stackup of tolerances
Implementation Method 2
As long as the voltage remains above a dropout level, the magnetic force generated by the coil is sufficient to maintain a plunger in a retracted position
Implementation Method 3
when the voltage drops below the specified value, a compression spring overcomes the magnetic force and extends the plunger out of the coil to actuate the trip mechanism of the circuit breaker
Data Source
AI summary
The reset lever on a circuit breaker undervoltage relay is actuated by translating arcuate movement of a handle arm pin as the circuit breaker handle is moved to the off position into rotation of the reset lever through a complaint interface lever that is stiff enough to actuate the reset lever, but flexible enough to accommodate for overtravel of the handle arm pin when the circuit breaker is reset and for the stackup of tolerances in the operating mechanism.