Siemens Aktiengesellschaft

Wolfgang Meusel

Hermann Waldmann

Thomas Matschullat

Manfred Weibelzahl

Arno Döbbeler

Wolfgang Hörger

Wolfgang Hoerger

Detlef Rieger

Wolfgang Kaufhold

Kurt Fork

Arno Doebbeler

Heinrich Blau

Ralf Engels

Kurt Schaumman

Heribert Niebergall

Werner Grohmann

Bernd Gortz

Flicker values to be expected may be determined and achieve a high probability from suitable state and operating variables which are acquired during the first minutes in the initial smelting phase. In this way, flicker can effectively be reduced and kept below predefined limiting values. This is in particular suitable during steel production using electric arc furnaces.

Flicker reduction in electric arc furnaces by means of flicker prediction from the state determination in the initial phase of the smelting process

In a power supply system for a three-phase arc furnace (), comprising at least one furnace transformer (), the furnace transformer () is connected on the secondary side to the three-phase arc furnace (). On the primary side, the furnace transformer () is connected to a three-phase supply mains () through an indirect converter (). The indirect converter () comprises at least one rectifier () on the mains side, at least one inverter () on the transformer side, and an intermediate circuit () between the rectifier () and the inverter (). Each phase of the three-phase supply mains () is connected to the intermediate circuit () through two converter elements () of the rectifier () in each case. Each primary-side phase of the furnace transformer () is connected to the intermediate circuit () through two converter elements () of the inverter () in each case.

Power supply system for a polyphase arc furnace with an indirect converter between a mains connection and a furnace transformer

A multilevel converter has a plurality of converter strands, which are connected to the phases of a three-phase-network in a star or delta connection. From phase voltage values and phase current values, an active component characteristic of the overall active current and two asymmetrical components characteristic of a distribution of the overall flowing active and reactive currents are determined. The active and the two asymmetrical components are each filtered and multiplied with the phase voltage values and the two filtered asymmetrical components. The multiplied values are then weighed and added to the phase current values. From the asymmetrical components and the phase voltage values, a zero current is determined and added to the phase current values such that it symmetrizes a potential asymmetrical active current flow that would occur without the zero current. From the modified phase current values, a control state for the converter strands is determined.

Multilevel converter as reactive power compensator having active

A static VAR compensator has several parallel compensation components (K&#x2013;K). To connect the static VAR compensator to an operating voltage (U) the compensation components (K&#x2013;K) are first successively connected to the operating voltage (U) by a control unit (CU) via a series resistor (R). The compensation components (K&#x2013;K) are only connected to the operating voltage (U) without series resistance once the aforementioned connection has been completed.

Connection method for a static VAR compensator

An arrangement for generating in each switching panel of a multipanel switching facility of an electrical power distribution network a digital operating-state image derived from command inputs and switching position signals. The digital operating state image is transmitted to a collecting memory arranged in a coupling panel which produces an overall image of all switching panels; which overall image is transmitted to the individual switching panels at periodic time intervals. A checking procedure is then conducted in the individual switching panels using the overall image. The arrangement utilizes microprocessors which are coupled to one another so as to exchange data via several transmission paths which are one-bit wide. This arrangement obviates the need for an interlock cable harness in the switching panels and cross-cabling between the switching panels.

System for error-protected operation of multipanel, power distribution

A circuit for damping hunting oscillations of controlled electric machines. The circuit is provided with a measuring circuit for determining the hunting oscillations and an identifier circuit for determining the angle components of such hunting oscillations. A phase shifter circuit is provided for receiving the angle components produced by the identifier circuit and forming a hunting oscillation correction signal which is shifted in phase from the hunting oscillations by a predetermined phase angle. The hunting oscillation correction signal is conducted to a control unit of the electric machine. The invention is particularly useful in damping hunting by the rotors of voltage controlled synchronous generators.

Circuit for damping hunting by electric machines

Ignition control signals for a multipulse controlled rectifier are combined in a sequence which is fed through a first time delay stage to a phase control circuit having a voltage-controlled oscillator which generates a phase-locked, gated, highly accurate square-wave oscillation as a trigger pulse series. The ignition control signals and the trigger pulse series of the voltage-controlled oscillator are conjunctively coupled in and gates are then amplified to form firing (ignition) pulses. A second time delay stage is provided for safety, in the event of dynamic control processes, and follows the first time delay stage. The output signals of the second time delay stage are linked to the ignition control signals in additional and gates and are subsequently amplified. Should the phase control circuit be unable to follow the changes of the ignition control signals in the event of dynamic changes in the control processes, the ignition pulse formed after the response delay of the second time delay stage is utilized.

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Herzogenaurach, Germany

Wolfgang Meusel