US 4,357,570 AGranted

Voltage compensation for an A-C network supplying a rapidly-changing load

AssigneeSiemens Aktiengesellschaft

InventorsEberhard Schmid, Wolfgang Kaufhold

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Abstract

A circuit for controlling the voltage of a network which supplies electrical power to a load having a rapidly varying impedance. The circuit contains a pair of controlled electric valves which are connected in parallel between two conductors of the network and poled for condition in opposite directions. A voltage transformer produces a signal corresponding to the network voltage, which signal is conducted to an integrator and subsequently compared to a preset mean value. The preset mean value corresponds to a desired amplitude at which the positive and negative half-wave cycles of the network voltage are desired to be maintained. In one embodiment, the controlled electric valves are caused to conduct current during respective half-waves of network voltage so as to maintain the amplitudes of the half-waves at the present mean value. Other features are described for compensating for long term drift of the network voltage and for controlling the controlled electric valves by means of logic circuitry.

Claims10

Dependent claims

A circuit for controlling a supply voltage between two conductors of an A-C network which supplies electrical power to a load having a rapidly changing impedance so as to maintain a half-wave mean supply voltage amplitude which corresponds to a predeterminable value, the circuit being of the type having at least a first controlled electric valve electrically disposed between the conductors, and a measuring device for producing a voltage signal responsive to the supply voltage on at least one conductor, the circuit being CHARACTERIZED IN THAT there is further provided:

valve control means for controlling the conduction state of the first controlled electric valve, said valve control means providing at least one firing pulse during a half-wave of the supply voltage which is of a first polarity so as to cause the first controlled electric valve to conduct, said firing pulse being responsive to a first signal corresponding to the difference between the amplitude of a first integration signal, corresponding to an integration of the voltage signal, and the predeterminable value;
and
supplementary firing signal means for producing a supplementary firing signal for placing the first controlled electric valve in a conductive state if the first controlled electric valve has been in a non-conductive state for a period exceeding a predetermined maximum time period.

Dependencies are inferred from the claim text.