Breaker Interlock System Preventing Trip Unit Removal
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Solution Overview
Problem
Circuit breakers without a trip unit are not trip-protected, leading to undesirable conditions where the circuit may not be protected without the trip unit being installed, and there is a need for a system to interlock the trip unit with the breaker to prevent disassembly when closed.
Innovation Solution
A breaker interlock system that includes an electronic trip unit for a multi-phase circuit breaker, where the circuit breaker is closable only when the trip unit is assembled and non-closable when not assembled, with a mechanism using solenoids to prevent disassembly of the trip unit while the breaker is in a closed configuration, and solenoids responsive to internal and external signals for tripping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If the trip unit is made removable from the breaker for servicing and replacement, then the ease of repair and adaptability are improved, but the reliability deteriorates because the circuit may not be trip protected without the trip unit being installed
Solution Approach 1:
The system performs preliminary actions by detecting whether the trip unit is properly installed before allowing the breaker to close. The control circuit checks for trip unit presence and prevents closure if the trip unit is missing, thereby ensuring trip protection is established before the circuit becomes energized. This resolves the contradiction by maintaining reliability while still allowing easy removal for repair.
Solution Approach 2:
The system uses feedback from the trip unit presence detection to control the breaker closure operation. The control circuit receives feedback about trip unit installation status and adjusts the breaker operation accordingly - allowing closure only when the trip unit is properly installed. This feedback mechanism ensures trip protection reliability while maintaining ease of repair capability.
2Ease of operation
If the breaker is allowed to close without verifying trip unit installation, then the ease of operation is improved, but the safety and reliability worsen due to lack of trip protection
Solution Approach 1:
The system performs a preliminary check to verify trip unit installation before allowing breaker closure. The control circuit detects trip unit presence and only permits closure when verification is successful, ensuring the circuit will have trip protection. This maintains ease of operation by providing a clear, automated verification process while ensuring reliability.
Solution Approach 2:
The control circuit acts as an intermediary between the breaker closure mechanism and the trip unit installation status. It mediates the closure operation by inserting a verification step that checks for trip unit presence, allowing closure only when the intermediary confirms proper installation. This resolves the contradiction by maintaining operational simplicity while ensuring protection reliability.
3Reliability
If an interlock mechanism is added to prevent disassembly of the trip unit when the breaker is closed, then the reliability is improved by ensuring continuous protection, but the device complexity increases
Solution Approach 1:
The control circuit performs multiple functions: it detects trip unit presence, controls breaker closure, and prevents trip unit removal when closed. By making the control circuit multi-functional, the system achieves reliable continuous protection without adding separate complex interlock mechanisms. This resolves the contradiction by maintaining reliability while minimizing added complexity through functional integration.
Solution Approach 2:
The system merges the interlock function with the existing control circuit rather than adding a separate mechanical interlock mechanism. The control circuit combines trip unit detection, closure control, and removal prevention into a single integrated electronic system, achieving continuous protection reliability without significant complexity increase.
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
Ensures the circuit breaker remains trip-protected by preventing disassembly of the trip unit when closed, ensuring the circuit is not energized without the trip unit and allowing controlled tripping through solenoids.
Implementation Method 1
The circuit breaker has a plurality of solenoids and each of the plurality of solenoids is in operable communication with the circuit breaker to trip the circuit breaker on command
Data Source
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AI summary
Disclosed herein is a breaker interlock system. The system includes, a trip unit for a breaker, and a breaker receptive of the trip unit. The breaker is closable when the trip unit is assembled thereto and the breaker is non-closable when the trip unit is not assembled to the breaker. The interlock system is further configured to prevent disassembly of the trip unit from the breaker when the breaker is in a closed configuration. The breaker having a plurality of solenoids and each of the plurality of solenoids is in operable communication with the breaker to trip the breaker on command. A first of the plurality of solenoids is responsive to a signal from the breaker via the trip unit, and a second of the plurality of solenoids is responsive to an externally supplied signal from a source other than the electronic trip unit.