Electromagnetic Relay Welding Detection Circuit
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Solution Overview
Problem
Conventional welding detection devices for electromagnetic relay switches require a large number of components and a complex configuration to detect the inductance of the excitation coil, making them cumbersome and inefficient.
Innovation Solution
A welding detection device with a driver circuit that applies voltage to the excitation coil based on the on and off states of a drive signal, and a welding detection circuit connected in parallel to the driver circuit, utilizing a fixed resistor to determine whether the movable contact is welded by analyzing a step input signal and transient response signal when the drive signal is in the off state, eliminating the need for a large-scale oscillation circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional welding detection device is used to detect the inductance of the excitation coil, then welding detection capability is achieved, but the device complexity and number of components increase significantly
Solution Approach 1:
The patent combines the welding detection circuit with the driver circuit by sharing common components (power supply, ground, and signal lines). The detection circuit is integrated into the existing driver circuit structure, eliminating the need for separate detection hardware. This merging approach maintains welding detection capability while significantly reducing device complexity and component count.
Solution Approach 2:
The driver circuit is designed to serve dual functions: driving the excitation coil and detecting welding conditions. By making the driver circuit universal, it can perform both actuation and detection tasks, eliminating the need for dedicated detection components and reducing overall system complexity while maintaining reliable welding detection.
2Measurement precision
If a large-scale oscillation circuit is used for welding detection, then detection accuracy is improved, but the number of components and circuit complexity increase
Solution Approach 1:
The patent extracts the essential detection function from the complex oscillation circuit and implements it using minimal components. By taking out only the necessary elements (fixed resistor and determination circuit) from the traditional oscillation circuit approach, the invention achieves accurate inductance detection with significantly fewer components.
Solution Approach 2:
The patent replaces the mechanical oscillation circuit approach with an electrical transient response measurement approach. Instead of using a physical oscillation circuit with multiple components, the invention uses electrical signal analysis (step input signal and transient response) to measure inductance, achieving the same detection accuracy with fewer components.
3Ease of operation
If the drive signal is applied continuously to the excitation coil, then the relay operates normally, but welding detection cannot be performed when the contact is in the on state
Solution Approach 1:
The patent implements periodic welding detection by temporarily interrupting the drive signal to the excitation coil at regular intervals. During these brief interruption periods, the determination circuit measures the inductance to detect welding conditions. This periodic action allows the relay to operate normally while periodically checking for welding, maintaining both ease of operation and welding detection capability.
Solution Approach 2:
The patent performs welding detection in advance by measuring inductance during drive signal interruption periods before the contact is actuated. This preliminary detection identifies welding conditions while the relay is still in the off state, allowing the system to prevent faulty operation before it occurs, thus maintaining reliability without compromising normal operation.
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 configuration allows for a simple and effective detection of the inductance of the excitation coil to determine if the movable contact is welded, reducing the complexity and number of components required, enabling reliable welding detection without the need for an oscillation circuit.
Implementation Method 1
an excitation coil 6 that controls the on and off states of a contact 80
Implementation Method 2
detecting an inductance of the excitation coil 6, and determines whether or not the movable contact 9 is welded, based on a step input signal and a transient response signal
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
A welding detection circuit (3) provided in a welding detection device (1) includes a determination circuit (4) determines whether the movable contact (9) is welded based on a step input signal and a transient response signal when a drive signal is in an off state. The transient response signal is generated so as to correspond to voltage less than or equal to operating voltage of the electromagnetic relay switch (5) according to an excitation coil (6) and a fixed resistor (R1).