Electrical transmission or interconnection systems – Switching systems – With operation facilitating feature
Patent
1997-08-11
1998-12-01
Paladini, Albert W.
Electrical transmission or interconnection systems
Switching systems
With operation facilitating feature
73 86, 324 712, 324421, 324700, 361 5, 361 6, H02H 326
Patent
active
058443312
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a switching device, in particular a contactor or circuit breaker, having contact elements that are mounted in a switching device housing on contact supports, and having an electrically insulated signal line as means for monitoring contact erosion, damage to or destruction of the insulator and/or the conductor being utilized to generate an external signal as an indication of the end of the service life of at least one of the contact elements.
BACKGROUND INFORMATION
The service life of switching contact elements is determined by erosion, i.e. by the gradual loss of contact material under the influence of the arc which occurs in the switching operation. Erosion will generally wear away the contact elements in non-uniform fashion. The service life ends when the contact material has either completely eroded away or has been removed to a defined minimum thickness at least at one point in the contact region.
At present, the state of the switch contact elements can be assessed in practice only by opening the switching device and by visual inspection. This is particularly true for the remaining expected service life, a knowledge of which is of central importance for the functionality of the switching device and thus for the operating reliability of the load unit being switched.
DE-OS 40 28 721 discloses a method for determining the remaining service life of switching devices, in which the charge that has flowed during a switching operation is electronically determined and summed for the switching operations. This method is in principle suitable not only for indicating a defined remaining service life, but moreover also for indicating the erosion state of the contact elements at any desired point in time. A comparatively large outlay for the associated electronics is necessary, however, so that profitability may exist only for large switching devices.
In addition, an earlier international patent application (PCT/DE 94/00244) that was not pre-published describes a switching device in which the contact elements are slotted on the rear side and installed on a split contact support. The remaining service life of the contact can be determined with this arrangement: when erosion has eroded away the material located over the slot, two contact halves are created. When switching takes place in this condition, a potential difference occurs between the two contact halves; this is measured as a voltage, and can be used as an indication of contact erosion. Lastly, Germany Patent Application No. 37 14 802 also describes an electronic switch in which a light guide, the transmission properties of which can be measured from outside by means of suitable auxiliary optical equipment, is associated with at least one of the contact elements. The intention in this context is that contact erosion which has progressed impermissibly leads to a change in optical transmission properties and ultimately to destruction of the light guide. In particular, provision is made that each of the contact elements must be fitted with a light guide of this kind.
Accordingly, it is an object of the present invention to provide a switching device with which detection and indication of a defined remaining service life during operation of the switching device are guaranteed in absolutely reliable fashion for all the contact arrangements together. In particular, implementation is to be economical even for smaller switching devices.
SUMMARY OF THE INVENTION
This object is achieved, according to the present invention, using an electrical signal line which is guided in a U-shape between the contact elements and the associated contact supports or in the contact material itself.
The insulated signal line consists either of doubly guided wires or a U-shaped loop with two insulated supply leads. In this context, the U-shaped loops of a measuring wire can be guided, insulated from one another, preferably in a metal-sheathed tube. Such lines are previously known, for example, as ungrounded sheathed thermocoup
REFERENCES:
patent: 5250909 (1993-10-01), Bitts
patent: 5420571 (1995-05-01), Coleman et al.
patent: 5453591 (1995-09-01), Stroud
patent: 5488530 (1996-01-01), De Jong
patent: 5747984 (1998-05-01), Amft et al.
Branston David-Walter
Kieser Jorg
Maier Reinhard
Voss Erich
Paladini Albert W.
Siemens Aktiengesellschaft
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