Contactor Economizer Failure Detection with BIT Hold Logic
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Solution Overview
Problem
Conventional electrical power generation and distribution system (EPGDS) contactors with built-in economizers face issues such as undetectable failures when the pull-in current is below the overcurrent threshold, leading to potential premature de-energization or failure to detect economizer failures, which can cause contactor tripping or premature failure in critical conditions.
Innovation Solution
A contactor driver circuit with an overcurrent status monitor and logic to detect economizer failures, including a falling edge delay circuit to keep the contactor active after failure detection, and integration with built-in test (BIT) and diagnostics systems to signal and communicate economizer failure status, ensuring continued operation and preventing premature contactor closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the economizer switches to hold mode with lower current, then power dissipation is reduced, but the failure becomes undetectable when pull-in current is below overcurrent threshold
Solution Approach 1:
The patent implements feedback by monitoring the overcurrent status monitor output to detect economizer failures. The system continuously monitors the current status and feeds this information back to the logic circuit, which then triggers appropriate responses (contactor opening or BIT indication) when a failure is detected, resolving the undetectability issue while maintaining energy efficiency.
Solution Approach 2:
The patent introduces an intermediary monitoring system consisting of the overcurrent status monitor and logic circuit. This intermediary detects economizer failures by monitoring current conditions and mediates between the economizer operation and the contactor control system, enabling failure detection without interfering with the energy-saving hold mode operation.
2Reliability
If the contactor drive circuit trips on overcurrent due to economizer failure, then the failure is detected, but the contactor is inadvertently de-energized
Solution Approach 1:
The patent applies preliminary action by detecting economizer failures through the overcurrent status monitor before they cause contactor tripping. The logic circuit identifies the failure condition and executes preventive actions (opening the contactor or generating BIT indications) in advance, preventing the harmful overcurrent tripping while maintaining reliable failure detection.
Solution Approach 2:
The system uses feedback from the overcurrent status monitor to detect economizer failures and triggers appropriate responses through the logic circuit. This feedback mechanism enables the system to respond to failures without causing inadvertent de-energization, as the monitored status directly controls the contactor operation only when necessary.
3Ease of operation
If the pull-in current is set below the overcurrent threshold to avoid tripping, then contactor operation is stable, but economizer failures become undetectable
Solution Approach 1:
The patent implements feedback by continuously monitoring the overcurrent status monitor output to detect economizer failures. This feedback mechanism allows the system to maintain stable operation with lower pull-in currents while still detecting failures through the monitoring system, which triggers appropriate responses when failures are identified.
Solution Approach 2:
The patent introduces an intermediary monitoring system that detects economizer failures independently of the overcurrent threshold setting. This intermediary system allows the pull-in current to be set below the overcurrent threshold for stable operation while maintaining failure detectability through the separate monitoring and logic circuitry.
Data Source
AI summary
A method includes detecting a failure in a contactor economizer that is configured to provide a first current to a coil of a contactor to close the contactor, and to provide a second current lower than the first current to the coil after the contactor is closed to hold the contactor closed. The method includes at least one of: driving contactor actuation based on economizer failure status; and/or signaling failure of the economizer through built in test (BIT) indication.