Switchgear Manual Control Plug Racking Interlock

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Solution Overview

Problem

Existing interlock structures for medium voltage circuit breakers require auxiliary voltage or special alignment features to prevent racking into or out of the connected position, which is not acceptable due to potential power outages or misalignment issues.

Innovation Solution

A mechanical interlock structure using a racking truck with a rotatable racking screw and linkage system that prevents racking without the control plug connected, engaging the racking linkage to block rotation when disconnected and allowing rotation when connected, eliminating the need for auxiliary voltage and reducing misalignment risks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a magnetic solenoid is used for interlocking, then the circuit breaker can be racked when auxiliary voltage is present, but the circuit breaker cannot be racked when auxiliary power is unavailable

Engineering Contradiction:

Improveracking operation reliabilityVSAvoidoperational flexibility without auxiliary voltage

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent replaces the magnetic solenoid (electromagnetic system) with a purely mechanical interlock system. The control plug physically blocks the racking path when disconnected, and the linkage mechanism translates plug insertion into release of the mechanical block, eliminating dependence on auxiliary voltage for the interlock function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The control plug serves as a mechanical intermediary that physically occupies the racking path when disconnected, preventing movement. When inserted, it acts as the mediating element that triggers the linkage to disengage the mechanical block, enabling racking without requiring electrical power.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If an automatic connecting auxiliary control connector is used, then racking can proceed without manual intervention, but misalignment between plug and socket occurs

Engineering Contradiction:

Improveautomatic racking operationVSAvoidplug and socket alignment

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The control plug is positioned to preemptively block the racking path before any racking motion can occur. This preliminary mechanical action prevents the need for precise alignment during the racking operation itself, as the plug must be fully inserted and seated before racking can begin, providing built-in alignment guidance.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The control plug and its receiving structure are designed with asymmetric geometry that guides proper alignment. The plug cannot be inserted incorrectly due to its unique shape and the corresponding asymmetric receptacle, eliminating misalignment issues while maintaining ease of operation.

Inventive Principle:

Principle #4Asymmetry

3Ease of operation

If the control plug is installed at the base of the racking truck, then racking can proceed, but alignment of plug and socket is required

Engineering Contradiction:

Improveracking operationVSAvoidplug and socket alignment

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The control plug is positioned in a different spatial dimension - not at the base of the racking truck, but in the racking path itself. This dimensional change allows the plug to directly block the motion path of the circuit breaker, eliminating the need for alignment with a separate socket while maintaining operational ease.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Enables secure racking of the circuit breaker into or out of the connected position solely through mechanical means, ensuring safety and reliability without auxiliary voltage or special alignment requirements, thus addressing the limitations of existing methods.

Implementation Method 1

a racking linkage associated with the racking screw and normally biased so as to be disengaged from the racking screw

Methodology Applied

Scientific EffectSpring bias: Spring

Implementation Method 2

a magnetic solenoid which blocks the racking of the circuit breaker when the manual control plug is disconnected. With this method, auxiliary control voltage, which is used to power the auxiliary features of the circuit breaker, energizes the magnetic solenoid and releases the interlock

Methodology Applied

Scientific EffectMagnetic solenoid: Solenoid

Data Source

PatentUS9490612B2Switchgear manual control plug racking interlock structure

Publication Date: 2016.11.08 ABB (SCHWEIZ) AG

AI summary

Interlock structure for a circuit breaker is constructed and arranged such that 1) when a control plug is disconnected from a socket, a portion of a linkage structure engages a racking linkage, causing a portion of the racking linkage to engage a racking screw, preventing the racking screw from rotating and thus preventing racking of the circuit breaker, and 2) when the control plug is connected with the socket, the linkage structure is actuated thereby moving the portion of the linkage structure to disengage from the racking linkage such that the portion of the racking linkage disengages from the racking screw, permitting the racking screw to rotate thereby permitting the circuit breaker to be racked to a connected position, where the primary contacts are connected to the main bus.