DC Switching Modules for Soft Current Path Disconnection
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Solution Overview
Problem
Existing switching devices for disconnecting current paths in DC supply systems with inductances at both ends face challenges in efficiently managing energy recovery and voltage surges, leading to complex and costly solutions, and fail to effectively address high-voltage issues during rapid disconnection.
Innovation Solution
A switching device comprising at least two series-connected switching modules, each with a controllable semiconductor switching element, a resistor, and a capacitor in parallel, allowing for a 'soft' switching process that reduces power losses and eliminates the need for expensive voltage-limiting components by managing energy transfer through switched-mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical switches are employed to disconnect the current path, then the disconnection can be achieved, but arc generation occurs and complex protective circuits are required
Solution Approach 1:
The patent replaces the mechanical switch with a semiconductor switching element (IGBT) that operates in the switched-mode domain. This substitution eliminates the arc generation problem inherent in mechanical switches while maintaining reliable disconnection capability. The semiconductor switch is controlled to open at appropriate moments, and the mechanical element serves only as a backup or for initial current interruption.
Solution Approach 2:
The patent introduces a capacitor connected in parallel with the semiconductor switching element as an intermediary component. This capacitor absorbs the energy from the inductances during the switching transition, preventing voltage spikes and eliminating the need for complex protective circuits like varistors. The capacitor acts as an energy buffer that mediates between the inductive load and the semiconductor switch.
2Speed
If semiconductor switching elements are used exclusively, then switching speed is improved, but voltage surges damage components and expensive voltage-limiting components are required
Solution Approach 1:
The patent connects a capacitor in parallel with the semiconductor switching element before switching operations occur. This capacitor is pre-charged and ready to absorb voltage surges that would otherwise damage the semiconductor component. The cushioning effect is prepared in advance, allowing the semiconductor switch to operate at high speed without fear of voltage spike damage.
Solution Approach 2:
The capacitor serves as an intermediary between the inductive energy storage and the semiconductor switching element. During switch-off, the capacitor absorbs the back-EMF generated by the collapsing magnetic field, protecting the semiconductor device. This intermediary component enables high-speed switching while maintaining component reliability.
3Productivity
If high-speed disconnection is implemented, then productivity is improved, but high voltages are generated that require protective circuits
Solution Approach 1:
The capacitor connected in parallel with the semiconductor switching element acts as an intermediary that absorbs the voltage surge generated during high-speed disconnection. When the switch opens rapidly, the inductance generates a back-EMF, but the capacitor provides a discharge path, limiting the voltage spike and eliminating the need for additional protective circuits.
Solution Approach 2:
The patent changes the operating parameters by using a capacitor to alter the voltage profile during switching. The capacitor's charging and discharging behavior modifies the voltage transient characteristics, allowing high-speed disconnection without generating damaging voltage surges. This parameter change enables fast switching while controlling the harmful voltage effects.
4Reliability
If complex protective circuits with varistors are added, then component protection is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the need for complex protective circuits with varistors by using a simple capacitor in parallel with the semiconductor switching element. This extraction simplifies the overall circuit while maintaining adequate protection against voltage surges. The solution removes unnecessary complexity while preserving the essential protective function.
Solution Approach 2:
The patent replaces expensive, complex protective components (varistors and multiple semiconductor elements) with a simple, inexpensive capacitor. The capacitor is a basic component that provides adequate protection without the complexity and cost of specialized voltage-limiting devices. This substitution reduces both component cost and circuit complexity while maintaining protection reliability.
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 disconnection of current paths with reduced power losses and lower component costs, allowing for reliable operation in high-voltage DC systems by prolonging the switch-off process and distributing energy removal across multiple modules, thus preventing component damage.
Implementation Method 1
a series circuit consisting of a resistor (14) and a capacitor (15) is connected in parallel
Implementation Method 2
a series circuit consisting of a resistor (14) and a capacitor (15) is connected in parallel
Data Source
AI summary
Various embodiments include a switching device for disconnecting a current path in a DC supply system, said current path comprising inductances at the source end and the load end, the switching device comprising: two series-connected switching modules; wherein each of the series-connected switching modules comprises a controllable semiconductor switching element and a series circuit; the series circuit including a resistor and a capacitor connected in parallel to the controllable semiconductor switching element.