GFCI Frequency Recognition for Stable Self-Testing
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Solution Overview
Problem
Existing GFCI devices face reliability issues due to unreliable self-tests when AC input frequency is not constant, leading to unnecessary trips and unsafe conditions, especially when used with non-standard voltage sources like generators or invertors, and are prone to noise interference.
Innovation Solution
A GFCI device that measures input voltage frequency to determine when to perform self-tests, including ground fault detection and solenoid operation checks, ensuring reliability by postponing tests until frequency is stable within a predetermined range and using frequency-based signal timing to avoid false trips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If self-tests are performed with assumption of constant 60Hz frequency, then device complexity is reduced, but measurement precision deteriorates when frequency varies
Solution Approach 1:
The patent performs preliminary frequency measurement and stability assessment before executing self-tests. This preliminary action allows the system to determine appropriate self-test parameters based on actual frequency conditions, improving measurement precision without significantly increasing overall device complexity. The frequency detection circuit and stability assessment algorithms are implemented as preparatory steps.
Solution Approach 2:
The patent introduces frequency detection and stability assessment as intermediary processes between the AC input and self-test execution. This intermediary layer analyzes frequency characteristics and provides guidance for appropriate self-test operation, enabling precise frequency-sensitive measurements while keeping the overall system architecture relatively simple.
2Reliability
If noise filtering is applied to improve self-test reliability, then false trips are reduced, but response time to actual faults increases
Solution Approach 1:
The patent applies noise filtering selectively and locally to specific signal processing stages rather than uniformly across all operations. Frequency-based signal timing and localized filtering at critical measurement points maintain self-test accuracy while preserving rapid response capability for actual ground faults. This localized approach resolves the contradiction between filtering effectiveness and response speed.
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
Enhances the reliability of GFCI devices by preventing false trips and maintaining safe operation across varying frequency inputs, ensuring consistent performance with non-standard voltage sources.
Implementation Method 1
A ground fault circuit interrupter (GFCI) device measures a frequency of an input voltage to the GFCI device
Data Source
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AI summary
A wiring device including an interrupting device, a fault detection circuit, and a testing circuit. The interrupting device electrically connects a line terminal to a load terminal when the interrupting device is in a reset condition and disconnects the line terminal from the load terminal when the interrupting device is in a tripped condition. The fault detection circuit is configured to detect a fault condition and generate a fault detection signal in response to detecting the fault condition, the fault detection signal is provided to the interrupting device to place the interrupting device in the tripped condition. The testing circuit is configured to determine a frequency of an input voltage at the one or more line terminals, perform a first test of the interrupting device at a first period of the frequency, and perform a second test of the fault detection circuit at a second period of the frequency.