Process and apparatus for measuring the apparent power fed to an alternating current consumer

Abstract

An apparatus and method are described wherein the apparent power fed to an alternating current consumer is measured by an active power measuring device or counter through which the current passes and which has a separate voltage input fed from an amplifier having two inputs. The first amplifier input receives a constant, limited auxiliary voltage which is induced from the current path and in phase with the consumer current. The second amplifier input is used for continuously adjusting the auxiliary voltage in accordance with the instantaneous value of the consumer voltage. For this purpose a comparing device, such as a bridge circuit, may be provided for comparing the consumer voltage with the voltage applied to the power measuring device. Variations in the comparison control can be transmitted, for example, by a small electric motor or a sample and hold circuit which in turn controls a solid state or other variable resistance device connected to the second input. In a further alternative, the second amplifier input may be a field plate which is subject to an electromagnetic flux controlled in accordance with the comparing device. In another example, a voltage divider is connected across the consumer voltage and has a center tap connected through a transistor to the second amplifier input.

Dependencies are inferred from the claim text.