Siemens Aktiengesellschaft

Wolfgang R&ouml;hl

Ulrich Baumg&auml;rtl

Holger Hochgraef

Ulrich Baumgaertl

Thomas M&uuml;ller

A method and circuit arrangement for measuring a current are described, which can be used in electrical engineering to precisely trigger electronic tripping devices in circuit breakers. The current is measured according to magnitude and phase in such a way that only the fundamental wave of the current between precisely determined current zero crossings is sampled at a low sampling rate, and the root mean square is calculated on the basis of the measured phase angle and amplitude. The exact phase angle is measured using a conventional PLL circuit with a downstream zero switch.

Method and circuit for measuring a current

An electronic tripping device for a circuit breaker contains circuitry for simulating the response curve of a fuse. This circuitry can be controlled by a single setting mechanism representing the nominal currents or rated currents of fuses. This improves the coordination of protection in sophisticated power supply equipment containing both circuit breakers and fuses. Tripping devices equipped with microprocessors or operating in an analog fashion can be configured for the mode of operation. The new protection system achieves particularly safe operation for the user in that the setting mechanism is combined with a rating plug for the &ldquo;fuse&rdquo; mode, thus directly setting the tripping device to one current value. In a manner similar to a true fuse, consequently, the setting mechanism is provided with appropriate labeling. The simulated curves may contain a point of inflection below a limit in a lagging manner, to increase the nominal switching capacity and selectivity limit of a circuit breaker.

Electronic tripping device for a circuit breaker

A circuit arrangement is described for monitoring an electronic tripping device for low-voltage switches having a microprocessor device which, in conjunction with a digital-analog converter, evaluates an overcurrent so that line power supply system. The microprocessor device (MPE) has a zero crossing comparator with which a constant test current pulse is transmittable, at zero crossings, to the electronic tripping device via an additional current transformer winding to measure the amplitude. In the case of deviations from the setpoint value, (re)calibration or actuation of the line tripping contacts, with an alarm signal being emitted, takes place.

Circuit arrangement for monitoring of an electric tripping device for low-voltage switches

An undervoltage circuit breaker has an electromagnet for triggering a switching device and a driver circuit that supplies power to the electromagnet. The driver circuit contains a pulse generator for generating a holding current for the electromagnet and a capacitance dimensioned so that delayed triggering of the electromagnet is possible. Due to the variable pulse duty factor of the pulse generator, the energy content of the capacitance is utilized favorably. An elevated operating voltage can also be selected and therefore a smaller capacitor may be selected to advantage.

Growing community of inventors

Berlin, Germany

Wolfgang Röhl

Growing community of inventors

Berlin, Germany

Wolfgang R&ouml;hl

Wolfgang Röhl