Abstract: A supply circuit for a fluorescent tube installation with a high-voltage transformer (T) which is connected, input-end, to a supply voltage with a frequency of several hundred Hz, and which is formed without an air gap. To replace the air gap in the transformer, an electronic regulator (EST) is nonetheless used in the supply circuit, which emulates the current-limiting function of an air gap. The frequency of the supply voltage is between 300 and 800 Hz, preferably 400 Hz. As these frequencies are higher than the usual network frequency of 50/60 Hz, the size and weight of the transformer can be considerably reduced.

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.