Electromagnetic Relay Coil-Current Detection for Contact Abnormalities
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Solution Overview
Problem
Existing electromagnetic relay detection methods face issues with false detection due to ambient temperature changes, power supply voltage variations, and inability to control voltage width, leading to increased costs and operational challenges.
Innovation Solution
The method employs first and second transient response signals of the coil current during detection pulse signals to accurately detect abnormal operations of the movable contact relative to the fixed contact, using a differential amplifier and control circuit to set thresholds based on these signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If step voltage is applied to detect opening and closing states, then detection capability is improved, but voltage width cannot be controlled leading to relay turn on during detection
Solution Approach 1:
The invention applies a pulse voltage with controllable duty cycle instead of a fixed step voltage. The duty cycle can be dynamically adjusted to control the voltage width, allowing the detection voltage to be applied for a controlled duration that prevents relay activation while enabling state detection.
Solution Approach 2:
The invention changes the voltage application parameters by using pulse width modulation (duty cycle control) to adjust the effective voltage width. This allows precise control over the detection signal characteristics without changing the peak voltage level, resolving the contradiction between detection capability and voltage width control.
2Measurement precision
If step voltage is lowered to enable detection during turn-off, then detection capability is improved, but relay cannot be turned on
Solution Approach 1:
The invention uses periodic pulse voltage application with controlled duty cycle. During detection periods, pulses are applied with low duty cycle for detection without activation. During operation periods, full voltage is applied for relay activation. This periodic switching resolves the contradiction between detection and activation requirements.
Solution Approach 2:
The duty cycle parameter is dynamically adjusted based on operational mode: low duty cycle during detection mode to prevent activation, and high duty cycle during operation mode to enable activation. This dynamic parameter adjustment allows the system to switch between detection and activation functions using the same voltage source.
3Reliability
If pulse signal duty is controlled to reduce false detection, then reliability is improved, but control complexity increases
Solution Approach 1:
The invention monitors the coil current transient response and compares it against expected characteristics to detect abnormalities. By using the current waveform feedback and analyzing its features (such as rise time or peak current), the system can identify welding conditions without requiring complex control mechanisms, thus improving reliability while maintaining simple control.
Solution Approach 2:
The invention replaces complex mechanical or circuit-based detection mechanisms with electronic signal analysis. By measuring and analyzing the electrical characteristics of the coil current transient response, the system achieves reliable abnormality detection using simple electronic components and software processing, reducing overall system complexity.
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
This approach effectively distinguishes between normal and abnormal operations of the electromagnetic relay, reducing false detections and cost by controlling pulse signal duty and setting adaptive thresholds, thus improving reliability and efficiency.
Implementation Method 1
a movable contact and a fixed contact are opened and closed by an electromagnetic force generated in accordance with supply or cutoff of a current passed through an excitation coil
Implementation Method 2
there is known a configuration that detects the inductance of the excitation coil to detect welding between the movable contact and the fixed contact
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
An abnormal operation of a movable contact is correctly detected. The abnormal operation of the movable contact (9) to the fixed contact (10) is detected based on at least one of a separation transient response signal of a coil current passed through the excitation coil (6) during the supply of a separation pulse signal and an attraction transient response signal of the coil current during the supply of an attraction pulse signal.