Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific circuit breaker or control structure
Patent
1992-12-24
1995-06-13
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific circuit breaker or control structure
335132, H01H 5000
Patent
active
054249007
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an electronic auxiliary contact for a electromechanical contactor having a movable slider and at least one switch element.
DESCRIPTION OF THE BACKGROUND ART
Conventional contactors employ mechanical auxiliary contacts according to FIG. 1 to accomplish different kinds of control and monitoring signals. The contact block is constructed with the help of a moving contact element a attached to the contact bridging member, said element carrying a portion of the circuit b of the auxiliary contact, said portion opening and closing the circuit c when said contact element is in either of its home positions. The contacts are sprung to attain longer mechanical life.
A mechanical contact is suitable for controls performed at conventional mains voltage levels, but developments in automation technology have set new demands on the quality of control and monitoring signals. Low voltage level and small current as well as precise timing of the signals are now desirable. Information on the position of a contactor's contact bridging member, for instance, can be signalled by means of mechanical auxiliary contacts, but this prior-art technique involves problems that compromise the reliability of obtained information. Bouncing of contacts at the opening and closing generates signal transients which cause jitter in the precise timing of events, and due to the mechanical play of contacts, the timing of the obtained signal has insufficient accuracy for positional monitoring of the contact bridging member. Moreover, contamination and oxidation of contact surfaces cause malfunctions, particularly at low current and voltage levels.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the above-described disadvantages and to achieve a novel system for obtaining and utilizing information on the positions of a contactor.
The system according to the present invention is based on the idea that the actuating element of the auxiliary contact operates without mechanically contacting the actual switch body of the auxiliary contact.
More specifically, the auxiliary contact according to the invention is characterized by a switch-activating element which incorporates at least one activating element and makes no mechanical contact with the switch element.
An electronic auxiliary contact according to the invention offers substantial benefits with respect to the conventional technology. Thus, a stable signal is obtained from the position of the contact bridging member, contact bouncing transients are avoided and the timing precision of the positional information is jitter-free. Due to the hermetic protection of the switch element, the characteristics of the auxiliary contact are not deteriorated by contamination or oxidation. The electronic auxiliary contact has no moving parts thus retaining a constant timing precision of the positional information even in extended use, and isolation problems are relieved by the mechanically noncontacting nature of the auxiliary contact switch circuit in respect to the moving pans.
The electronic auxiliary contact can provide reliable positional information for a process control computer also from a circuit operating at a low supply voltage. The position of the contactor's contact bridging member can be determined with an extremely high precision. The electronic auxiliary contact has a simple construction, and by integrating more electronics to it, possibilities of multiple different monitoring function are feasible not ever attainable at a sufficient accuracy by means of a mechanically operating auxiliary contact. A single auxiliary contact block can incorporate one or more position sensors, thus making it possible to detect various intermediate positions complementing the conventionally indicated home positions.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while i
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patent: 4236149 (1980-11-01), Soyck
patent: 4467300 (1984-08-01), Harbauer
patent: 4757213 (1988-07-01), Tiggs et al.
patent: 4945256 (1990-07-01), Tada et al.
patent: 5189789 (1993-03-01), Taylor
Kiiskinen Esko
Rajala Erkki
Solanti Petri
ABB Stromberg Kojeet Oy
Gaffin Jeffrey A.
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