GB432106A - Improvements in or relating to automatic voltage regulating means - Google Patents

Abstract

432,106. Automatic electromechanical regulators; supply systems; converting; motors. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, GIBSON, J. W., and TAYLOUR, H. H., c/o General Electric Co., Witton, Birmingham. Jan. 15, 1934, Nos. 1463 and 5198. [Classes 35, 38 (ii), and 38 (iv)] An automatic voltage regulator comprises means rotated at a constant speed, means rotated at a speed which is a function of the voltage to be controlled, means operated in dependence upon variations in the ratio of the two speeds for effecting control of the voltage and means for varying the speed ratio in accordance with the load-current. The voltage of a grid controlled arc discharge rectifier is automatically controlled by affecting the timing of its grid excitation in response to the movement of the intermediate member 24 of an electrical or mechanical differential gear one element 21 of which is rotated at a speed responsive to the voltage of the rectifier and the other element 22 at a constant speed. The elements 21, 22 are alternators excited with A.C. and having their stator windings connected to the rotor and stator respectively of a torque motor 23 driving an arm 27 through a worm 25, so as to control the phase position of brushes 30 of a distributer 28 which are fed with timed impulses for grid control of the rectifier by a contact 29 rotated by a synchronous motor 12 from the A.C. mains. The shaft of the machine 22 is driven by a shunt motor 15 energized from D.C. mains and arranged to run at a constant speed by a governor controlled resistance 18. The motor 15 may be clock controlled and may be of the saturated shunt type or it may be a synchronous motor driven from the A.C. mains. The machine 21 is driven by a motor 6 the armature of which is connected across a potential divider connected to the output D.C. from the rectifier and the excitation is provided by a constantly excited field winding 9 and a winding carrying the load current of the rectifier or a current proportional thereto. In a modification the standard speed motor and the voltage responsive motor drive worm shafts which co-operate with a common worm wheel which operates the control arm of the distributer through a pin-and-slot connection. The control in accordance with the loading of the rectifier may be arranged to act on the constant speed motor, as by control of a governor or the like thereon, or it may be provided in the form of a compounding or de-compounding winding on the voltage responsive motor. If a de-compounding winding is provided a drooping voltage-load characteristic is obtained. If a compounding winding is provided arranged to saturate part of the yoke of the motor stator at a particular value of load current, a rising voltage characteristic is obtained which levels off or drops at a predetermined value of load. If this excitation is obtained through rectifiers on the A.C. side of a converter control of the voltage of an A.C. circuit supplied through the converter may be obtained. The grid control of the converter may be of the type in which a normal negative bias on the grids thereof is removed by positive pulses from a synchronous distributer or it may be of the type in which the wave shape of a peaky voltage supplied from a saturable transformer is controlled by a potentiometer in the circuit of the D.C. saturating winding. The excitation of the winding 9 on the motor 6 may be adjustable by a rheostat 14 to adjust the voltage required across the rectifier output. The Provisional Specifications disclose arrangements in which the motor 6 is provided with an additional field winding for improving load sharing between parallel connected units. In an arrangement in which a grid controlled arc converter operates in parallel with a levelcompounded rotary converter, this additional winding is connected to the junction of the compounding winding and the armature and to the junctions of the cathode of the rectifier and a smoothing choke connected to the same bus-bar as the compounding winding. When the rotary converter is not operating the winding is open circuited. In a further modification in which the regulator is associated with rectifying and inverting converting plant the compounding windings on the motor 6 are changed or varied so that the characteristics during rectification and inversion are different. Specification 431,784 is referred to.