Electricity: electrical systems and devices – Safety and protection of systems and devices
Patent
1998-04-02
1999-08-03
Gaffin, Jeffrey
Electricity: electrical systems and devices
Safety and protection of systems and devices
361102, 335201, H02H 300
Patent
active
059333030
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns a device for protection against overload of the switch contacts of a switching device that has a switching mechanism for opening and closing the switch contacts, where the switch contacts can be separated under the influence of a high current against the action of the switching mechanism, forming an electric arc.
BACKGROUND INFORMATION
A protection device, for example, is described in German Patent No. 40 22 078 A1. A tripping shaft that belongs to the switching mechanism and can be activated by a release is provided as a component of the protection device. The release can in turn be influenced by the current flowing over the switching device. If the switch contacts are separated immediately by the forces associated with such a high current flow, the switching mechanism is released directly by the opening operation of the switch contacts, and thus a complete shutdown is brought about. The switching mechanism is released by a displaceable guidance of the tripping shaft against a restoring force with a reduction in coverage between the latching surfaces provided on a latch and on the tripping shaft.
Furthermore, it is known that the gas pressure that occurs when the switch contacts are opened in the arc quenching chamber of a switching device can be used for immediate actuation of the switching mechanism. Therefore, a pressure seal is provided for the switching mechanism and is connected to the arc quenching chamber by a pipeline (European Patent No. 455,561 A1).
Furthermore, it is possible to consider using methods which are known in another context for controlling a switching device and make it possible to detect a movement of a switch contact. This includes in particular an analysis device that measures the capacitance between the switch contacts and generates from it a signal for contact opening. Furthermore, a relative movement of a switch contact can be detected by a drive organ which is connected to the movable switch contact and is provided with a reflector, with an optical waveguide in a stationary mount opposite it a slight distance away. On the end facing away from the reflector, the optical waveguide acts together with a light source and a receiving circuit for reflected light. However, such devices as described in German Patent No. 39 05 822 A1 are relatively expensive supplementary devices of a switching device that need their own power supply and for whose electronic analysis circuits hardly any space is available in the casings of compact switching devices. On the other hand, the devices that operate mechanically according to the aforementioned German Patent No. 40 22 078 A1 and European Patent No. 455,564 A1 require a special structural adjustment to the desired operation with forced tripping when the switch contacts are raised.
Another restriction on the protection devices described above is that they can be used only in combination with switching devices having a switching mechanism that can be controlled by automatic devices. This condition is generally met with power circuit-breakers and contactors, but not with isolating switches.
SUMMARY OF THE INVENTION
An object of the present invention is to design a protection device against overload of the switch contacts of a switching device that has a switching mechanism for opening and closing the switch contacts, where the switch contacts can be separated under the influence of a high current against the action of the switching mechanism thereby forming an electric arc so that switching devices of various types can be protected from an excess current overload by an inexpensive device that can be added on easily.
According to the present invention, the aforementioned object is achieved by the fact that an electric energy transducer arranged in the vicinity of the switch contacts is exposed to electromagnetic radiation associated with the electric arc, and the energy transducer converts received electromagnetic radiation into a current for operation of the protection device. The prese
REFERENCES:
patent: 5185684 (1993-02-01), Beihoff et al.
patent: 5185685 (1993-02-01), Tennies et al.
patent: 5185686 (1993-02-01), Hansen et al.
patent: 5185687 (1993-02-01), Beihoff et al
Gaffin Jeffrey
Sherry Michael J.
Siemens Aktiengesellschaft
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