Contactor Coil Current Detection for Welded and Stuck Faults
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Solution Overview
Problem
Contactors may fail to operate correctly due to issues such as being welded closed, the plunger becoming stuck, or unexpected movement, which are not effectively detected in existing systems.
Innovation Solution
A detection controller is used to monitor coil current changes and patterns to identify fault modes, including determining if the contactor is welded closed, if the plunger is stuck, or if it unexpectedly moves, by applying predetermined voltage and current thresholds and patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contactor operates without detection mechanisms, then the device complexity is reduced, but the reliability deteriorates due to undetected failure modes
Solution Approach 1:
The contactor performs self-diagnostics by monitoring its own coil current characteristics. The control circuit analyzes current patterns during energization and holding phases to automatically detect failure modes such as welded contacts, stuck plungers, or unexpected movements, eliminating the need for external detection devices.
Solution Approach 2:
The system implements feedback by continuously monitoring coil current and comparing it against expected patterns. When deviations are detected (such as abnormal current magnitude or unexpected current changes), the system generates feedback signals to indicate failure modes, enabling real-time reliability monitoring.
2Reliability
If detection methods are added to monitor contactor state, then the reliability improves, but the device complexity increases
Solution Approach 1:
The control circuit serves multiple functions: it controls the contactor operation and simultaneously performs failure mode detection by analyzing coil current characteristics. This multi-functionality eliminates the need for separate dedicated detection hardware, reducing overall system complexity while maintaining reliability.
Solution Approach 2:
The patent replaces potential mechanical detection methods (such as physical sensors or switches) with electrical current analysis. By substituting mechanical monitoring systems with electrical field-based detection through coil current measurement, the system achieves simpler implementation and fewer moving parts.
3Measurement precision
If the coil current is continuously monitored at high levels, then the detection precision improves, but the energy consumption increases
Solution Approach 1:
The system performs detection during specific periodic phases of contactor operation (energization phase and holding phase) rather than continuous monitoring. The control circuit measures coil current at these critical moments to detect failure modes, reducing overall energy consumption while maintaining detection precision when needed.
Solution Approach 2:
The system applies detection effort selectively during critical operation phases rather than continuously. By monitoring coil current only during energization and holding phases when failure modes are most likely to manifest, the system achieves adequate detection precision with reduced energy expenditure compared to continuous high-level monitoring.
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 detection controller improves the safety and reliability of contactors by accurately identifying and addressing these fault modes, ensuring proper operation.
Implementation Method 1
the coil may be configured to be energized with a current or a voltage
Implementation Method 2
the detection controller measures a first amount of time for a magnitude of a coil current of the coil to exceed a first predetermined current threshold
Data Source
AI summary
Methods and apparatuses for failure mode detection in a contactor are disclosed. In a particular embodiment, a method for failure mode detection in a contactor includes maintaining the contactor command signal in the open state; connecting the contactor to a voltage supply that supplies a first predetermined voltage amount to the contactor; measuring a first amount of time for a magnitude of a coil current of the coil to exceed a first predetermined current threshold; determining whether the first amount of time exceeds a first predetermined time threshold; responsive to determining that the first amount of time does not exceed the first predetermined time threshold, determining that the contactor is in the open state; and responsive to determining that the first amount of time exceeds the first predetermined time threshold, determining that the contactor is in the closed state.