Electricity: electrical systems and devices – Safety and protection of systems and devices – Load shunting by fault responsive means
Reexamination Certificate
2011-04-12
2011-04-12
Fureman, Jared J (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Load shunting by fault responsive means
Reexamination Certificate
active
07924538
ABSTRACT:
The invention relates to a protective circuit for an electrical device operated in particular in an explosion-hazard area, with a limiting circuit connected downstream of a pair of input terminals for limiting an output voltage present at a pair of output terminals and/or an output current delivered at the output terminals below a threshold value and a shorting circuit, which shorts the output or input terminals when a threshold value is exceeded, the control signal that controls the limitation originating from the same place as the signal that triggers the shorting circuit, and with a measuring circuit, which uses the output voltage or the output current to provide a control signal, which is fed on the one hand to a final control element for reducing the output voltage or the output current and on the other hand to the shorting circuit, the measuring circuit comprising a ZENER diode and/or a measuring resistor and the control signal being a voltage that is in particular a transistor-amplified or impedance-converted voltage. To minimize the difference between the guaranteed output voltage and the safety voltage, the invention proposes that the final control element is a self-conducting field-effect transistor, at the gate of which the control signal is present, and the measuring circuit is connected downstream of the field-effect transistor in the direction of current flow.
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Fureman Jared J
Hoang Ann T
St. Onge Steward Johnston & Reens LLC
Werner Turck GmbH & Co. KG
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