Double-Contact Switch Vacuum Arc-Free Commutation
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Solution Overview
Problem
Conventional switching devices for high currents, especially those handling direct currents and low-frequency currents, face increased thermal loads and reduced service life due to longer arc durations and higher energy content in switch arcs, which complicates arc quenching and leads to material burnup and insulation capacity reduction.
Innovation Solution
A double-contact switch with vacuum switching chambers, where two movable electrodes are pressed onto fixed contacts using contact compression springs with different spring forces, allowing for temporal offset in opening the contact pairs and utilizing a power semiconductor switch to prevent arc formation by commuting the load current to zero before the second contact pair opens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional air-operated switching arrangements are used for high currents, then the switching device can handle high currents, but temporal fluctuations during switching make arc-free switching difficult and extend arc duration
Solution Approach 1:
The patent employs a vacuum switching chamber instead of air-operated switching. In the vacuum environment, metal vapor from evaporating contact material forms the arc, and this vapor condenses out within a few microseconds at the zero-current case, enabling virtually instantaneous reconsolidation of the switching path without an ionizable gaseous atmosphere. This eliminates the temporal fluctuations present in air switching and achieves arc-free switching for high currents.
2Adaptability or versatility
If direct currents or low-frequency currents are switched, then the switching device can handle these current types, but the reduced or absent periodicity of current zero crossing leads to longer arc duration and higher energy content
Solution Approach 1:
The vacuum switching chamber provides an inert environment where metal vapor arcs formed during switching condense out rapidly at the zero-current case. This mechanism works effectively for direct currents and low-frequency currents where zero crossings are reduced or absent, as the vacuum environment inherently limits arc duration and energy content regardless of current type.
Solution Approach 2:
The power semiconductor switch is controlled to briefly have low resistance before the mechanical contacts open, preemptively commutating the arc current to the parallel power semiconductor switch. This preliminary action ensures that when the contacts disconnect, the current is already transferred to the semiconductor path, enabling arc-free switching even for direct currents without periodic zero crossings.
3Duration of action of moving object
If hybrid switches with power semiconductor are used, then arc time is reduced, but the mechanical bridge switching arrangement causes temporal fluctuations that make arc-free switching difficult
Solution Approach 1:
The vacuum switching chamber eliminates the air atmosphere that causes ionization and temporal fluctuations during switching. In this inert vacuum environment, the hybrid switch achieves reliable arc-free operation as metal vapor condenses instantly at zero current, removing the medium that sustains arcs and causes switching fluctuations.
Solution Approach 2:
The power semiconductor switch is activated in advance to briefly conduct current before the mechanical contacts open. This preliminary commutation action ensures that when the mechanical switching occurs in the vacuum chamber, the current is already transferred to the semiconductor path, guaranteeing arc-free switching without temporal fluctuations.
4Productivity
If conventional switching devices handle high currents, then the switching function is achieved, but material burnup and thermal load increase, reducing service life
Solution Approach 1:
The vacuum switching chamber provides an inert environment that prevents continuous arc formation and material erosion. Metal vapor from contact material evaporates during switching but condenses instantly in the vacuum, preventing the sustained arcs that cause material burnup in air-operated devices. This preserves contact material while maintaining high current switching capability.
Solution Approach 2:
The power semiconductor switch commutates current before the mechanical contacts open, preventing arc formation at the contacts entirely. This preliminary current transfer to the semiconductor path eliminates the thermal and erosive effects of arcs on contact material, significantly reducing burnup and extending service life.
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 approach enables virtually arc-free switching of high direct and low-frequency currents, reducing material burnup and thermal loads, thereby increasing the service life of the switching device and allowing for efficient handling of high currents without significant arc formation.
Implementation Method 1
a first contact compression spring (51) configured to apply a first spring force to the first movable electrode (11) in such a way that the contact of the first electrode is pressed onto the fixed contact (41)
Implementation Method 2
in a vacuum switching chamber a metal vapor arc of evaporating contact material is formed in a vacuum switching chamber when the contacts are disconnected under load, and condenses out in the interior of the vacuum chamber within a few microseconds
Implementation Method 3
the power semiconductor is controlled in such a way that it briefly has a low resistance, in such a way that the arc current flowing through the mechanical switch is briefly commuted to the parallel power semiconductor switch
Data Source
AI summary
A double-contact switch has first and second tubular vacuum switching chambers; a stationary electrode, between the first and second vacuum switching chamber, having a first stationary contact protruding into the first chamber and a second stationary contact protruding into the second chamber; a first electrode, arranged in the first chamber, moveable axially therein, having a contact support region and sealed off from the first chamber exterior; a second electrode, arranged in the second chamber, moveable axially therein, having a contact support region and scaled off from the second chamber exterior; a first contact compression spring applying a first spring force to the first movable electrode so the first electrode contact presses onto the contact protruding into the first chamber; and a second contact compression spring applying a greater, second spring force to the second movable electrode so the second electrode contact presses onto the contact protruding into the second chamber.