Drive Circuit Protection Against Excitation Coil Short Circuits
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Solution Overview
Problem
Existing electromagnetic flowmeters face issues with circuit protection due to repeated stopping and restarting of excitation current supply, leading to deterioration and potential breakdown, especially when excessive current flows through the excitation coil, causing noise and heat generation.
Innovation Solution
A drive circuit with a transformer, power supplier, and electromagnetic driver is designed to detect excessive excitation current and prevent its supply by using a current detection resistance and power control circuit, limiting power to the primary winding and controlling the excitation current based on voltage thresholds, thereby preventing repeated cycles of power supply interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection circuit turns off the supply of excitation current when reference voltage exceeds a predetermined value, then the circuit is protected from excessive current, but noise may cause repeated stopping and restarting of current supply leading to circuit deterioration
Solution Approach 1:
The patent applies preliminary action by introducing a delay mechanism before the protection circuit activates. When the reference voltage exceeds the threshold, the circuit does not immediately turn off the excitation current, but waits for a predetermined time period to confirm sustained excessive current condition. This prevents noise-induced false triggering while maintaining protection functionality, thereby extending circuit lifespan without compromising reliability.
Solution Approach 2:
The patent implements beforehand cushioning by adding a time delay buffer between the detection of excessive current and the activation of protection. This cushioning period allows transient noise to dissipate before the protection mechanism engages, preventing repeated on-off cycling that would deteriorate the circuit. The delay acts as a protective buffer that distinguishes between temporary noise and genuine fault conditions.
2Reliability
If excitation current is repeatedly stopped and restarted due to noise, then circuit protection is activated, but excessive heat generation and over-rating occur causing circuit breakdown
Solution Approach 1:
The delay mechanism serves as preliminary action that prevents premature protection activation. By waiting for a predetermined time period after the threshold is exceeded, the system confirms that excessive current is sustained rather than transient. This prevents repeated stopping and restarting of excitation current, thereby avoiding cumulative heat generation and over-rating that would lead to circuit breakdown.
Solution Approach 2:
The patent introduces periodic action through the delay mechanism that creates a time-based filtering effect. Instead of immediate response to threshold crossing, the system periodically checks whether the excessive current condition persists beyond the delay period. This periodic verification prevents noise-induced oscillations and the associated heat generation, while still providing protection against genuine sustained overcurrent conditions.
3Ease of operation
If power supply voltage decreases due to excessive excitation current, then signal processing circuit stops operation, but the circuit cannot forcibly continue stopping current to protect itself
Solution Approach 1:
The delay mechanism acts as preliminary action that prevents the signal processing circuit from stopping due to voltage fluctuations caused by transient noise. By requiring the excessive current condition to persist for a predetermined time, the system avoids unnecessary operation interruptions. Simultaneously, this preliminary verification ensures that when protection is truly needed, the circuit can maintain its stopping state without being reset by noise, preserving self-protection capability.
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 solution effectively protects the circuit from excessive excitation current, preventing deterioration and breakdown, while allowing for safe operation and notification of failures, thus extending the lifespan of the electromagnetic flowmeter components.
Implementation Method 1
a transformer configured to transmit electric power supplied from the power supplier to the electromagnetic driver
Implementation Method 2
a power supplier configured to supply electric power to the transformer
Implementation Method 3
an electromagnetic driver configured to supply an excitation current of AC to the excitation coil in accordance with electric power transmitted by the transformer
Data Source
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AI summary
A drive circuit includes a primary power supplier which supplies a primary electric power in accordance with a state of the drive circuit, a secondary power supplier which supplies an operation electric power and an excitation electric power, an excitation current supplier which supplies an excitation current to an excitation coil, a power supply monitor which compares the voltage value of the operation electric power with a voltage threshold and outputs monitoring information, and a controller which determines whether a short circuit has occurred in the excitation coil based on the monitoring information, and stops supplying the excitation current if the short circuit has occurred. The voltage threshold is higher than a lowest voltage value with which the controller operates, and the voltage threshold is a voltage value representing that the short circuit has occurred in the excitation coil.