Relay Coil Current Detection for Contactor Movement Faults
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Solution Overview
Problem
Existing relay systems lack effective methods for detecting malfunctions, particularly in safety-critical applications like battery disconnect units in electric vehicles, which can lead to potential failures such as fire or explosion.
Innovation Solution
A method and system using a peak detector to compare coil current against dynamic thresholds, identifying anomalies in back electromotive force (BEMF) pulses and other metrics to detect relay faults, including contact bounce and improper movement, and generating an indication of a faulty state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If relay systems operate without fault detection methods, then device complexity is reduced, but reliability deteriorates due to potential failures in safety-critical applications
Solution Approach 1:
The relay system performs self-diagnosis by monitoring its own coil current characteristics. The control unit analyzes back electromotive force (BEMF) pulses and current waveforms generated during normal relay operation to detect faults, eliminating the need for separate external detection devices and maintaining system simplicity while improving reliability.
Solution Approach 2:
The system continuously monitors coil current feedback during relay operation and compares it against expected characteristics. The control unit receives real-time current data, analyzes BEMF pulse patterns, and detects deviations indicating faults such as contact bounce or improper movement, enabling proactive fault detection without additional hardware complexity.
2Measurement precision
If dynamic threshold tracking is implemented to detect coil current anomalies, then measurement precision is improved, but device complexity increases due to additional detection circuitry
Solution Approach 1:
The existing control unit is enhanced to perform multiple functions: it continues to control relay operation while simultaneously acting as a fault detection system. The same processor analyzes coil current waveforms and generates fault indications, eliminating the need for separate dedicated detection hardware and reducing overall system complexity while maintaining high measurement precision.
Solution Approach 2:
The system dynamically adjusts detection thresholds based on real-time coil current characteristics. The control unit tracks positive and negative peak currents, adapts threshold values according to operating conditions, and modifies detection parameters to optimize precision across varying temperatures and electrical conditions without requiring complex fixed-threshold circuitry.
3Reliability
If multiple fault detection metrics are monitored simultaneously, then reliability is improved through comprehensive fault coverage, but device complexity increases due to multiple sensors and processing requirements
Solution Approach 1:
The relay system uses its own operational characteristics as detection sources. The control unit analyzes back electromotive force (BEMF) pulses naturally generated during contactor movement, examines coil current waveform patterns during switching, and evaluates timing characteristics of relay activation - all without requiring external sensors or additional measurement equipment, achieving comprehensive fault detection through self-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
Enhances fault detection in relays, preventing potential failures by identifying malfunctions early, thus ensuring the reliability and safety of critical systems.
Implementation Method 1
Relays are electro-mechanical devices that play a crucial role in controlling electrical circuits. They act as switches that can open or close an electrical connection when an external signal is applied.
Implementation Method 2
detecting whether the relay is in a faulty state includes identifying a count of artifacts of back electromotive force (BEMF) action in the comparison signal
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
A method comprising: generating, by a peak detector, a comparison signal by comparing a coil current of a relay against a dynamic threshold, the comparison signal having a first value when the coil current is above the dynamic threshold, the comparison signal having a second value when the coil current is below the dynamic threshold, wherein the peak detector is configured to: cause the dynamic threshold to track the coil current until a positive peak in the coil current is reached that has a value PP, and set the dynamic threshold to a rebound value R in response to detecting that a negative peak in the coil current is reached, the rebound value R being based on the value PP; detecting whether the relay is in a faulty state based on the comparison signal; and generating an indication of a fault when the relay is in a faulty state.