Protective Switch Reclosing Lock Until Electrical Reset
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Solution Overview
Problem
Existing protective switching devices lack a mechanism to prevent premature manual re-closure of contacts after an overload or short circuit, which can lead to further damage to electric devices if the underlying issue has not been resolved.
Innovation Solution
A method and device that utilize a trigger mechanism with a latch and spring, where the transition from a tripped state to a preloaded state is inhibited until an electrical reset signal is received, ensuring the contact remains open until the circuit is safe, using a trip actuator and lock with a lever and spring, and electrical resetting via a voltage change or motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the operator manually resets the latch by moving the handle, then the contact of the protective switching device is closed again, but the electric device may be exposed to excess current causing further damage
Solution Approach 1:
The control device performs a preliminary check of the circuit status before allowing manual reset. The control device evaluates whether the circuit is in a safe state (no excess current detected) before enabling the handle to close the contact, thus preventing premature reset operations that could cause damage
Solution Approach 2:
The control device continuously monitors the circuit status and provides feedback to the operator through the user interface. The device only permits manual reset when sensors confirm the circuit is safe, creating a feedback loop that ensures protection is maintained while allowing operation when appropriate
2Speed
If the contactor is used to switch off the circuit, then the response time is sufficient for overload, but the contactor may weld and fail to open
Solution Approach 1:
The protective switching device is pre-configured to take over circuit interruption if the contactor fails. When the contactor welds and cannot open, the protective switching device's trip mechanism can still operate to open its contact, providing a backup interruption path
Solution Approach 2:
The system incorporates a redundant protective switching device as a cushion against contactor failure. This backup device ensures that even if the contactor welds, the circuit can still be interrupted through the protective switching device's contact
3Loss of time
If the protective switching device allows manual re-closing, then the device can be quickly reset, but premature reset may occur before the circuit is safe
Solution Approach 1:
The control device monitors circuit parameters through sensors and provides feedback before allowing reset. Only when the feedback indicates safe conditions (normal current levels, no faults detected) does the device enable manual re-closing, thus preventing premature reset while maintaining quick restoration when safe
4Reliability
If a second contactor is added to ensure circuit interruption, then reliability improves, but device complexity increases
Solution Approach 1:
The protective switching device is designed to perform multiple functions: it provides overload protection, short-circuit protection, and serves as a backup interruption device if the contactor fails. This multi-functionality eliminates the need for a second contactor, maintaining reliability while reducing complexity
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
Prevents erroneous re-closure of the contact, ensuring the electric device is not exposed to excess current until the circuit is safely reset, thereby reducing the risk of further damage and potentially eliminating the need for a second contactor in safety motor starters.
Implementation Method 1
a trigger mechanism (140) which can be preloaded into a first, preloaded state by moving a handle (130) from an off-position to an on-position
Implementation Method 2
the excess current in the circuit causing the overload is transformed into a trip signal by sensors and evaluation electronics
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Manual re-closing of a contact of a protective switching device 100 is inhibited as long as an electrical reset has not yet occurred. A trigger mechanism 140 of the switching device is preloaded into a first, preloaded state by manually moving a handle 130, which results in a closed contact state of the switching device. In response to an excess current due to an overload and/or a short circuit or another external trigger input, the trigger mechanism 140 is tripped and transits to a second, tripped state, opening the contact 110 of the switching device. A transition from the second, tripped state back to the first, preloaded state is inhibited despite moving the handle 130, as long as an electrical reset signal indicating re-establishment of a safe condition has not yet occurred. Said electrical reset signal resets the trigger mechanism. The electrically reset trigger mechanism can finally be manually reset to the preloaded state, in which the contact is closed, by moving the handle. A safety motor starter (700) comprises a contactor (710) and a motor protective switching device (720).