Abstract: A field lighting network providing for individual control of the light fittings while reducing overall cable costs. A converter unit converts a supply voltage obtained from an A.C. main to a substantially constant current in a Boucherot circuit with a series resonance circuit, tuned to the main frequency. The converter unit includes a Boucherot circuit having a series resonance circuit, substantially tuned on the main frequency, and an additional inductance in series with a load connected to the converter unit. A regulator unit supplied with current couples to each fitting or group of fittings for individual regulation of the current passing through the respective lamp or lamps. Each regulator unit is disposed to receive control information on the power cable.

Abstract: An inverter connection has an inverter bridge which, in series with a controllable valve, is connected between terminals for connection to a direct voltage source. A turn-off circuit is arranged for simultaneous turn off of the thyristors of the inverter. The turn-off circuit comprises a capacitor connection and a thyristor connection which is controllable in both directions. The latter is connected, in series with at least one capacitor, between a point which is located between the valve and the bridge, and at least one of the terminals. An inductor is arranged in at least two of the three current paths between said point and the terminals.

Abstract: A convertor connection for connection to a DC circuit includes current sensing members for forming a quantity corresponding to the direct current of the convertor connection. An indicating arrangement is provided for indicating asymmetrical operating conditions, which includes a first band pass filter connecting to the current sensing members which let through frequencies in a frequency band located between zero and the fundamental frequency of the AC component during undisturbed operation. When the output signal of the first filter exceeds a predetermined value, through a second filter an asymmetry indicating signal is emitted. The release of an output signal is prevented by a delay arrangement if the duration of the asymmetrical operating condition is less than a predetermined time.

Abstract: A load levelling system for connection to an alternating current network includes an electro-chemical direct current source and line-commutated controllable convertor means having DC terminals connected to the supply source and AC terminals for connection to the network. A continuously reactive power generating system composed of a fixed capacitor battery and a line-commutated reactive convertor is connected to the AC terminals. The convertor means may include a first convertor and a second convertor, the first convertor having a higher rated voltage than the second, with a control angle arrangement for the first convertor. The convertors are series-connected through their DC terminals and have a transformer connecting their AC terminals.

Abstract: A load levelling system for connection to an alternating current network includes an electro-chemical direct current source and line-commutated controllable convertor means having DC terminals connected to the supply source and AC terminals for connection to the network. A continuously reactive power generating system composed of a fixed capacitor battery and a line-commutated reactive convertor is connected to the AC terminals. The convertor means may include a first convertor and a second convertor, the first convertor having a higher rated voltage than the second, with a control angle arrangement for the first convertor. The convertors are series-connected through their DC terminals and have a transformer connecting their AC terminals.