Siemens Aktiengesellschaft

Wolfgang Roehl

Henry Franke

Andreas Pancke

Holger Hochgraef

Hans Rehaag

Ulrich Baumgaertl

The circuit contains a primary coil on the core () of a magnetic circuit with an air gap and switchable into a line carrying the measurement current. A secondary compensation coil (), with an order higher winding count and mounted on the core, is connected to the output of a controllable compensation current source (). The output of a Hall element () in the air gap is connected to the control input of the compensation source. A further coil () on the core is connected to an additional controllable current generator () whose control input () is driven by a measurement device () for the compensation current via a control and evaluation circuit (). USE/ADVANTAGE&#x2014;Measuring a.c. and d.c. Can be produced at low cost and all drift occurring during measurement can be compensated.

Method for reproducing direct currents and a direct current transformer for carrying out said method

In order to provide as short a switching delay as possible in an undervoltage release which contains an electromagnet for tripping a switching device, and a driver circuit feeding the winding of the electromagnet, with the driver circuit being used to produce a pulsed holding current for the electromagnet, an electronic switch is fitted in the self-holding circuit that is produced via a freewheeling diode. This electronic switch can be driven as a function of the output signal from an undervoltage detector which is arranged within the driver circuit.

Under voltage release with an electromagnet and clocked holding current circuit

A process for controlling an overcurrent tripping device of a high-speed d.c. circuit breaker. The input voltage can reach a signal evaluation device for current rise rate via two different paths. The tripping of the high-speed d.c. circuit-breaker is no longer fundamentally delayed by the unavoidable delay experienced by signals applied to a filtering device. A path for the input voltage, existing in parallel to the filter path can be designed such that when the current rises very steeply, the unfiltered (and thus also undelayed) signal reaches the signal evaluation device (i.e., the signal bypasses the filter and is applied to the signal evaluation device) whereas, when the current rises more slowly, the filtered signal is evaluated.

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Berlin, Germany

Wolfgang Roehl