Electronic Trip Unit Comparator Circuit for Nuisance Tripping
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Solution Overview
Problem
Conventional electronic trip units experience nuisance tripping due to microcontroller malfunctions and PCB noise at low power levels, leading to invalid trip signals.
Innovation Solution
An electronic trip unit incorporating a comparator circuit that filters trip signals using a first comparator to validate the signal against a reference voltage and a second comparator to ensure the power supply is stable, preventing false tripping by determining if the trip signal is based on a valid fault event.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electronic trip unit operates at low power levels, then energy consumption is reduced, but nuisance tripping occurs due to microcontroller malfunctions and PCB noise
Solution Approach 1:
A comparator circuit is introduced as an intermediary between the microcontroller and the trip actuation mechanism. The comparator validates trip signals by comparing them against a reference voltage, filtering out noise and spurious signals generated at low power levels while allowing genuine trip events to pass through.
Solution Approach 2:
The system implements feedback through the comparator that continuously monitors the trip signal and reference voltage. When the trip signal exceeds the reference voltage (indicating a valid fault condition), the comparator provides feedback to confirm the trip event, otherwise it suppresses invalid signals.
2Power
If the microcontroller operates in RESET toggling condition at low voltage, then the electronic trip unit can function with reduced power, but noise pickup on PCB tracks causes false trip signals
Solution Approach 1:
The comparator acts as an intermediary filtering stage between the noisy microcontroller environment and the trip actuation system. It references the trip signal against a stable reference voltage, effectively rejecting PCB noise and spurious signals that do not meet the threshold criteria for valid trip events.
Solution Approach 2:
The system changes the voltage threshold parameter dynamically by using the comparator to establish a minimum reference voltage level. Trip signals must exceed this parameter threshold to be considered valid, thereby filtering out low-level noise that occurs during RESET toggling conditions.
3Reliability
If a comparator circuit is added to validate trip signals, then nuisance tripping is reduced, but device complexity increases
Solution Approach 1:
A single comparator circuit serves as an efficient intermediary that provides comprehensive trip signal validation. This minimal addition to the circuit architecture achieves reliable noise filtering and signal validation without requiring complex multi-stage filtering or additional processing components.
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 solution effectively reduces nuisance tripping by distinguishing between valid and invalid trip events, ensuring the circuit breaker only trips when a genuine fault occurs, thereby enhancing reliability and accuracy.
Implementation Method 1
a first comparator which receives the trip signal from the processing unit and compares the trip signal with a predetermined reference voltage
Implementation Method 2
a second comparator which compares a voltage generated by a power supply with the predetermined reference voltage
Implementation Method 3
The generated trip pulse is then used to turn on a MOSFET which energizes a solenoid/flux shifter to trip the circuit breaker
Data Source
AI summary
An electronic trip unit which includes a processing unit and a comparator circuit. The processing unit receives an input voltage, and a reset signal to reset the electronic trip unit, and generates a trip signal when sensed current of the electronic trip unit exceeds a predetermined threshold. The comparator circuit includes a first comparator which receives the trip signal from the processing unit and compares the trip signal with a predetermined reference voltage determined based on the reset signal, and a second comparator which compares a voltage generated by a power supply with the predetermined reference voltage. The comparator circuit determines whether the trip signal is for a valid trip event based comparison results of the first comparator and the second comparator.