GB312396A - Improvements relating to alternating current voltage regulators - Google Patents

Abstract

312,396. Lunn, J. R. P. Feb. 27, 1928. Regulation, automatic. - In voltage regulators in which tappings of the secondary of a boosting transformer are selectively included in circuit by a regulator switch operated by a motor started by a voltage-relay and in which the motor is maintained in operation, by a pilot switch moving with the regulator switch, until the regulator switch has passed completely on to the next tapping, the pilot switch has two sets of contacts so arranged that the motor is reversed if it overruns. The fixed or moving contacts, or both, of the regulator switch are of carbon and the voltage difference between successive tappings is such that the transformer windings are not overheated by short-circuit currents when two contacts are bridged. As applied to 4-wire, 3-phase circuits, the outgoing and incoming lines b, c, Fig. 5, are connected to transformer windings d<1> - d<3>. e<1> - - e<3>, tappings on the windings e<1> - - e<3> being joined to contacts f<1> - - f<3> connected by sliding carbon brushes h to contacts g<1> - - g<3>. The brushes h are mounted in a common holder reciprocated by a screw driven by the reversible motor k. The motor turns in one direction or the other on closure of one of two switches x, each operated by solenoids u. The reciprocated brush holder carries an additional contact l cooperating with bars having notches opposite the contacts f. On the occurrence of low or high voltage, one coil u is energized through the corresponding holding coil sand over- and under-voltage contacts p<2>, p<1> of the relay r. The contact l leaves the notches in the bars m, n and contacts with one or both of the bars to energize the coil u directly and to short-circuit the holding coil s so that the relay r can return to its neutral position as soon as the voltage, is normal, the contacts p<1>, p<2> of the relay not carrying current during this return. After such return, as soon as the control l comes over notches in the bars m, n, the coil u is de-energized and the motor stops in a position in which each brush h does not bridge two contacts f. The notches in the bars m, n are staggered so that, if the contact l over-runs this position under the momentum of the motor, it will first make contact with the bar connecting the motor to run in the reverse direction. Instead of reciprocating, the switch may be rotated by the motor through worm gearing. Switches z<1>, z<2> de-energize the coil u at the limits of travel of the brush holder. Each carbon brush u may comprise several carbon blocks each spring-pressed and insulated by mica from each other but all in contact with the holder.