Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific quantity comparison means
Patent
1996-09-05
1998-04-07
Fleming, Fritz
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific quantity comparison means
361 99, 361 93, H02H 318
Patent
active
057371679
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention refers to a residual current safety switch of a type including a residual current transformer and an evaluation circuit connected therewith and controlling an electromagnetic trigger device for actuation of switching contacts, and further including an overvoltage protection circuit, e.g. in form of a voltage-dependent resistor.
Conventional residual current safety switches of this type (hereinafter called short "DI-switch") effect the voltage supply of the electronic components via an auxiliary contact connected to a power line either before the residual current transformer or after the residual current transformer. This solution has the drawback that the electronic components as well as the pertaining overvoltage protection remain unprotected, and excessive power supply may lead to a defect of this protection, or in case of outage of voltage supply to the electronic components, without any capability to recognize such a defect from outside.
SUMMARY OF THE INVENTION
It is the object of the invention to eliminate these drawbacks and to provide a DI-switch of the afore-described type, which protects the installed overvoltage protection as well as the voltage supply circuit of the electronic components.
In accordance with the invention, this is attained with a residual current safety switch of the afore-stated type by connecting an evaluation switch and/or the overvoltage protection circuit to power outlets for supply of voltage when the switching contacts are closed through lines, with one line extending through the residual current transformer and the other line being guided outside the residual current transformer, wherein the supply current of the electronic components and/or the current that flows through the overvoltage protection circuit is lower than the triggering current when the nominal voltage is applied.
Through these measures, the occurrence of static overvoltages, of excessive power supply, or a defect of the voltage supply of the electronic components results in an activation of the trigger device. Thus, the residual current safety switch is capable to separate itself from the power supply at particular defects or overloads of the electronic components to eliminate any risk that the malfunction of the switch remains unnoticeable under certain conditions.
According to another feature of the present invention, the overvoltage protection circuit is connected parallel to the evaluation circuit, and the trigger device is connected in series to this parallel connection. This is advantageous as an adjustment of the sensitivity of the overvoltage protection over a wide range is effected, without significantly influencing the evaluation circuit, whereby a remaining impact can be taken into account during configuration and dimensioning of the evaluation circuit.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be described in more detail with reference to the drawings, with FIGS. 1, 2, 3 schematically illustrating different embodiments of a DI-switch according to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The DI-switch according to FIG. 1 is connected by the fixed conductors of both its switching contacts 1, 2 to power outlets L, N. Positioned downstream of these switching contacts 1, 2 is a residual current transformer 3 which has a secondary winding 4 connected to the evaluation circuit 5 that evaluates an encountered secondary current caused by residual current.
The evaluation circuit 5 is connected to an electromagnetic trigger device K1 for controlling the switching contacts 1, 2 and an auxiliary contact 6 which separates the electronic components from the power outlet independently from the power supply end or consumer end of the DI-switch.
The voltage supply of the evaluation circuit 5 is effected via the electromagnetic trigger device K1 as well as via the lines 7, 8 and the preceding auxiliary contact 6, with one of both lines 7 or 8 (line 8 in the attached Figure) extending through the residual current transformer 3 a
REFERENCES:
patent: 4015169 (1977-03-01), Misencik
patent: 4618907 (1986-10-01), Leopold
patent: 5195008 (1993-03-01), Harr
EH SCHRACK Energietechnik GmbH
Feiereisen Henry M.
Fleming Fritz
Sherry Michael J.
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