SCR Switching Arrangement With Bypass Commutation for Short-Circuit Currents
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Solid state circuit breakers face issues with resistance and heating due to semiconductor elements in the main line, leading to reduced lifetime and inefficiencies in switching off high rising currents, particularly short circuit currents.
Innovation Solution
A switching arrangement incorporating a silicon controlled rectifier (SCR) with a bypass line and resonant circuit, including a capacitor and inductance, allows for low resistance and efficient switching off of high currents by utilizing a control unit to manage the switching process, ensuring low voltage drop and reduced heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If semiconductor elements are placed in the main line for switching operations, then switching capability is improved, but resistance and heating increase
Solution Approach 1:
The circuit is divided into a main line with mechanical switch and a parallel bypass line with semiconductor elements. The mechanical switch handles continuous current with low loss, while semiconductors are segmented to only activate during switching operations or fault conditions, thereby reducing overall heating.
Solution Approach 2:
A bypass line acts as an intermediary path that allows current to flow through semiconductor elements only when needed for switching or protection, rather than forcing all current through semiconductors. This mediator approach minimizes the time semiconductors conduct high current, reducing heating.
2Loss of energy
If mechanical switch is used in the main line, then resistance and losses are reduced, but switching speed decreases due to delay
Solution Approach 1:
The system merges the advantages of mechanical switches (low resistance, low losses) with semiconductor switches (fast switching) by combining them in a hybrid arrangement where the mechanical switch provides the main current path and semiconductors provide fast switching capability during transient conditions.
Solution Approach 2:
Semiconductor elements are pre-positioned in the bypass line and can be activated immediately to handle switching transients before the mechanical switch completes its operation, effectively pre-compensating for the mechanical switch's slower response time.
3Productivity
If semiconductor elements are used for switching off high rising currents, then switching capability is improved, but voltage drop and heating increase
Solution Approach 1:
The current path is segmented into a main line with mechanical switch and a parallel bypass line. During normal high current operation, the mechanical switch carries the bulk current with minimal voltage drop. Semiconductor elements are segmented to only activate during switching transients or fault conditions, minimizing their contribution to overall voltage drop and energy loss.
4Loss of energy
If SCR-arrangement is used, then low resistance in on state is achieved, but switching off capability is lost
Solution Approach 1:
An auxiliary switching element acts as an intermediary to provide the switch-off capability for the SCR. When the auxiliary switch opens, it interrupts the holding current path, forcing the SCR to turn off. This mediator approach allows the SCR to maintain its low on-state resistance while gaining switch-off capability through the auxiliary element.
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 enables efficient switching of high currents with low voltage drop and reduced heating, effectively handling high slew rates of short circuit currents, thereby improving the reliability and lifespan of circuit breakers.
Implementation Method 1
A commutation circuit, connected in parallel with the SCR, turns off the SCR by utilizing a resonant circuit to divert the SCR current after the switch opens.
Data Source
Figure 1~3
Figure 4~5
AI summary
A switching arrangement (1) for switching off an electric current with a high slew rate, especially a short-circuit current, it is suggested, that the switching arrangement (1) comprises - a main line (2) with a first SCR-arrangement (3) comprising at least a first SCR (4) and a first reverse conducting diode (5) arranged in parallel to the first SCR (4), - a first bypass line (6) connected to the main line (2) and arranged in a parallel way to the first SCR-arrangement (3), - the first bypass line (6) comprises a second SCR-arrangement (7) comprising at least a second SCR (8) arranged in the same polarity as the first reverse conducting diode (5), - the first bypass line (6) further comprises at least one capacitor (9) and a DC-voltage source (10) connected to the capacitor (9) for pre-charging the capacitor (9).