Relay Contactor Movement Detection Using Dynamic Coil Current Thresholds
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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 fault detection system that monitors the back electromotive force (BEMF) pulses of relay contactor movement, comparing amplitude and duration against predefined thresholds to identify anomalous movements, and uses a peak detector to track coil current dynamics, setting dynamic thresholds to detect potential failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If relay systems operate without fault detection mechanisms, then device complexity is reduced, but reliability deteriorates due to undetected malfunctions in safety-critical applications
Solution Approach 1:
The relay system performs self-diagnosis by monitoring its own coil current characteristics. The detection circuit analyzes the natural electrical signatures of the relay coil during operation to identify malfunctions such as contactor failure, eliminating the need for external diagnostic equipment or complex additional sensing mechanisms.
Solution Approach 2:
The system detects faults by monitoring changes in electrical parameters, specifically coil current amplitude and duration. By establishing baseline parameter ranges for normal operation and detecting deviations from these parameters, the system can identify malfunctions without requiring complex mechanical or optical detection mechanisms.
2Measurement precision
If dynamic threshold tracking is implemented to detect positive peaks, then measurement precision improves for detecting relay activation, but device complexity increases due to continuous parameter monitoring
Solution Approach 1:
The threshold for detecting coil current peaks is made dynamic rather than fixed. The threshold automatically adjusts based on the tracked maximum current value, allowing the system to adapt to varying operating conditions and maintain high detection precision without requiring complex calibration procedures or multiple fixed thresholds.
Solution Approach 2:
The system uses feedback from the monitored coil current to continuously update the detection threshold. By feeding back the maximum detected current value and using it to set the threshold for the next detection cycle, the system maintains high precision while using a relatively simple circuit architecture.
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 tolerance in relays by accurately identifying impending failures, preventing operational issues and ensuring safety in critical applications.
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
A fault detection system that monitors the back electromotive force (BEMF) pulses of relay contactor movement
Data Source
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.