Electricity: measuring and testing – Determining nonelectric properties by measuring electric... – Erosion
Patent
1995-09-22
1998-05-05
Nguyen, Vinh P.
Electricity: measuring and testing
Determining nonelectric properties by measuring electric...
Erosion
324415, 324537, 324700, 340644, 73 86, G01R 3100, H01H 7104
Patent
active
057479844
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a switching component, and particularly relates to a safety switch or a power switch, with contact parts attached to a contact carrier, including a portion for detecting contact erosion.
In switching components, burning erosion occurs on the contact parts with each switching operation. Depending on the stress due to the current or voltage, this erosion ultimately leads to failure of the switching component. This is especially true when switching short-circuit currents in power switches, because the resulting arcs cause an especially great erosion of the contact surfaces.
Erosion mainly limits the lifetime of a switch. Currently, the contact parts or even the entire switch must be routinely replaced after a certain lifetime, regardless of whether there has actually been any considerable amount of erosion of the contact parts.
Several proposals in the state of the art have been made that would permit monitoring of the erosion of contact parts, such as detecting contact erosion using accessory electric, mechanical or X-ray equipment. For example, German patent (ALS) 2,405,149 discloses a switching component where the change in switch travel length due to contact erosion is detected. In order to achieve a reliable display of the contact erosion, however, a relatively complicated mechanical design is necessary.
In addition, German patent (OLS) 3,714,802 discloses an electric switch in which at least one of the contact parts is provided with an optical fiber whose transmission properties can be measured externally by means of suitable optical equipment. Due to an appropriate arrangement of the optical fiber, excessive contact erosion leads to destruction of the optical fiber and thus to a change in the optical transmission properties. However, introducing optical fibers into the contact parts to be applied to the contact carriers requires an additional production step. Therefore, such contact parts including incorporated optical fibers are also expensive and difficult to handle as a part of integrated production of switching components.
SUMMARY OF THE INVENTION
The present invention relates to a switching component including other devices for monitoring the contact erosion. In the switch according to the present invention, the end of the lifetime of the contact parts can be predicted without interrupting the operation of the switch or having to open the switch housing.
In the present invention, the contact carrier is split (sub-divided) and the contact parts are slotted at the rear and are mounted on the split contact carrier. The contact carrier is preferably split asymmetrically and the contact parts are preferably slotted asymmetrically at the rear. Both moving and fixed contact carriers can be used with the contact parts in this regard.
In the switching device according to the present invention, the contact carriers that are joined together when the contact parts are new become separated when contact erosion becomes great enough. The resulting change in physical conditions can be detected easily. The detection may take place on the basis of the oscillational behavior (vibrational behavior) of the contact bridge by mounting an oscillation sensor (vibration sensor) on the contact bridge or mounting a microphone in the housing. As another example, the voltage between the two contact carriers can be measured to provide a signal for contact erosion at least during the switching operation.
In the present invention, it is especially advantageous that the prerequisites for detecting contact erosion may be created merely by a slight change in the design of the contact carrier and the respective contact parts. The sensors can be mounted inside the switch housing or on the outside of the switch housing.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional details and advantages of the present invention may be derived from the following description of embodiments of the invention in conjunction with the attached drawings.
FIG. 1 illustrates a contact carrier wi
REFERENCES:
patent: 3272949 (1966-09-01), Lawrence
patent: 4225819 (1980-09-01), Grau et al.
patent: 4479117 (1984-10-01), Marquardt
patent: 4700082 (1987-10-01), Oguma et al.
Amft Dietrich
Branston David-Walter
Kieser Jorg
Maier Reinhard
Brown Glenn W.
Nguyen Vinh P.
Siemens Aktiengesellschaft
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