Thyristor Rail Potential Limiter with Feedback Control
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Solution Overview
Problem
Existing devices for limiting rail potential in DC railways are not reliable in detecting and discharging dangerously high voltages, as they may fail to maintain a conductive connection until the current falls below a threshold value, leading to incomplete discharge.
Innovation Solution
Incorporating a thyristor with a voltmeter-connected firing input and an ammeter in the connecting line, where the control unit continuously measures current and re-ignites the thyristor if the setpoint is exceeded, ensuring a continuous conductive connection to the building ground until the current falls below a target value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical switching device is used to switch the connecting line between rail and building ground, then the device structure is simple, but the reliability of detecting and discharging high rail potential is insufficient
Solution Approach 1:
The patent replaces the mechanical switching device with an electronic thyristor-based switching system. The thyristor is controlled by electrical signals from the control unit based on measurements from the voltmeter and ammeter, eliminating mechanical moving parts and improving reliability in detecting and responding to high rail potential conditions.
Solution Approach 2:
The patent implements a feedback control system where the control unit continuously monitors voltage via the voltmeter and current via the ammeter, processes these measurements, and automatically controls the thyristor switching based on predetermined threshold values. This closed-loop feedback mechanism ensures reliable detection and response to high rail potential conditions.
2Reliability
If the switching device interrupts the connecting line as soon as voltage falls below threshold, then the switching operation is quick, but the current may still be too high causing incomplete discharge
Solution Approach 1:
The control unit uses feedback from both the voltmeter (voltage measurement) and ammeter (current measurement) to determine when to interrupt the connecting line. The system continuously monitors both parameters and only interrupts the connection when both voltage and current fall below their respective threshold values, ensuring complete discharge of rail potential.
Solution Approach 2:
The control unit is programmed with predetermined threshold values for both voltage and current. When the voltage exceeds the voltage threshold, the control unit immediately triggers the thyristor to close the connecting line, establishing the discharge path before the current reaches dangerous levels. This preliminary action ensures rapid response to high potential conditions.
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 solution ensures reliable and complete discharge of the rail potential to the building ground by maintaining a conductive connection as long as the current exceeds the threshold value, preventing premature interruption and ensuring safety.
Implementation Method 1
a voltmeter 3 is located between a rail 1 of a DC railway and the building ground 2, in which it is also determined whether the measured voltage exceeds a threshold value
Implementation Method 2
an ammeter 7 is integrated into the connecting line 4 and is connected to a control unit 8
Implementation Method 3
the switching device has a thyristor with whose firing input the voltmeter is connected, and that an ammeter is integrated into the connecting line, which is connected to the firing input of the thyristor via a control unit
Data Source
AI summary
The invention relates to a device and a method for limiting the rail potential in a DC railway, a low-impedance link (4) being arranged between the rail (1) and the ground (2) below the structure. A switchgear (6) which is connected to a voltmeter (3) via a control line is connected to the link (4), the voltmeter (3) being arranged between the rail (1) and the ground (2) below the structure. According to the invention, the switchgear (6) comprises a thyristor (5), to the triggering input of which the voltmeter (3) is connected. An ammeter (7) which is connected to the triggering input of the thyristor (5) via a control unit (8) is connected to the link (4). Said control unit (8) keeps re-triggering the thyristor (5) until the value of the current has dropped below a threshold value.