Rapid Cutoff Device for SCR DC Switches
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Solution Overview
Problem
Conventional mechanical and active switch elements face challenges in efficiently cutting off currents in DC circuits due to the absence of phase shift, leading to increased manufacturing costs, reduced reliability, and potential damage from electric arcs.
Innovation Solution
A rapid cutoff device for SCR DC switches, which includes a thyristor DC switch connected with a capacitor that is charged by the DC circuit to rapidly lower the current to zero when the drive signal stops, preventing electric arcs and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical switch elements are applied in DC circuits, then switching off capability is provided, but manufacturing cost and dimensions increase due to high electric arc elimination capability requirements
Solution Approach 1:
The patent introduces a capacitor as an intermediary element connected in parallel with the thyristor switch. This capacitor absorbs the electric arc energy generated during switching off operation, protecting the thyristor from damage without requiring complex mechanical switch structures. The capacitor acts as a mediator that handles the harmful electric arc effects, enabling simple thyristor-based switching with improved reliability and reduced complexity.
2Speed
If active switch elements like MOSFETs or IGBTs are used, then rapid current cutoff and no electric arc are achieved, but endurability of voltages and currents decreases
Solution Approach 1:
The patent combines the advantages of different switch types by merging thyristor elements (high voltage and current endurability) with a capacitor-based arc suppression circuit (rapid cutoff capability). The thyristor provides robust voltage and current handling, while the parallel capacitor enables rapid current cutoff and absorbs electric arc energy, achieving both high speed switching and high reliability that neither element alone could provide.
3Reliability
If thyristor switch elements are applied in DC circuits, then high voltage and inrush current endurability are provided, but complete current cutoff cannot be achieved due to no phase shift current
Solution Approach 1:
The patent converts the harmful effect of continuous current in DC circuits (which prevents natural thyristor cutoff) into a beneficial mechanism. By connecting a capacitor in parallel with the thyristor, the continuous current is redirected to charge the capacitor during switching off operation. This transforms the problematic continuous current flow into a useful charging process that naturally reduces the thyristor current to zero, enabling complete cutoff while maintaining high voltage and current endurability.
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 and rapidly cuts off currents in thyristor DC switches, enhancing reliability and reducing manufacturing costs by eliminating the need for complex phase shift mechanisms.
Implementation Method 1
a capacitor (21) serially connects with the switch (20)... the capacitor (21) is charged by the first DC circuit (1)... to rapidly lower a current of the thyristor DC switch (10) for approaching a zero value
Data Source
AI summary
A rapid cutoff device includes a thyristor DC switch, a switch and a capacitor. An operation method includes: connecting the thyristor DC switch between a first DC circuit and a second DC circuit; serially connecting the switch and the capacitor which further parallel connects the first DC circuit; when the thyristor DC switch is conducted, supplying a DC current via the thyristor DC switch; when a drive signal of the thyristor DC switch stops, operating the switch to conduct the capacitor which is charged by the first DC circuit to rapidly lower a current of the thyristor DC switch approaching a zero value, thereby rapidly cutting of the thyristor DC switch.