Contactor Economizer Failure Detection to Prevent Premature Tripping
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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 in critical aerospace applications.
Innovation Solution
A contactor driver circuit with an overcurrent status monitor and logic to detect economizer failures, including a falling edge delay circuit to maintain contactor actuation and communication with built-in test systems, ensuring continued operation and signaling of failures to prevent premature contactor closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the economizer switches to lower current hold mode, then power dissipation in the contactor coil is reduced, but the failure of the economizer may not be detectible if the pull-in current is below the overcurrent threshold
Solution Approach 1:
An overcurrent status monitor is introduced as an intermediary component that continuously monitors the current status of the contactor coil. This monitor detects overcurrent conditions that indicate economizer failure, providing a reliable failure detection mechanism independent of the pull-in current magnitude. The monitor acts as a mediator between the coil circuit and the control logic, enabling failure detection even when operating currents are below traditional overcurrent thresholds.
Solution Approach 2:
The system implements feedback through the overcurrent status monitor that continuously provides status information about the coil current to the control logic. This feedback mechanism allows the system to detect economizer failures by monitoring current anomalies, enabling the control logic to respond appropriately by preventing contactor opening or signaling failures through BIT indications.
2Reliability
If the economizer fails in pull-in mode, then the coil drive circuitry may trip on overcurrent and deenergize the contactor, but this causes premature contactor opening and loss of function
Solution Approach 1:
The overcurrent status monitor performs preliminary detection of overcurrent conditions before they cause contactor deenergization. By detecting the economizer failure early through current monitoring, the system can take preliminary protective action through the control logic to prevent the contactor from opening, thereby maintaining system function while still protecting against the failure condition.
Solution Approach 2:
The control logic provides beforehand cushioning by implementing logic that prevents contactor opening when economizer failure is detected. This protective logic acts as a cushion against the harmful effect of premature contactor opening, allowing the system to maintain contactor closure even when the economizer fails, thereby preventing loss of critical function while the failure is signaled for maintenance.
3Device complexity
If conventional overcurrent monitoring is used, then simple protection is provided, but failures with pull-in current below threshold are undetectible
Solution Approach 1:
The system replaces traditional mechanical or simple thermal overcurrent protection mechanisms with an electronic overcurrent status monitor that provides continuous digital monitoring of coil current. This substitution enables much higher measurement precision and sensitivity, allowing detection of current anomalies that indicate economizer failure even when operating currents are below traditional overcurrent trip thresholds.
Data Source
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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 (114) to close the contactor (114), and to provide a second current lower than the first current to the coil after the contactor (114) is closed to hold the contactor (114) 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.