Patent GB-710382-A (GB)
Title: Improvements in or relating to magnetic amplifiers
IPC: H03F9/04
Filed: 1952-02-22
Abstract: 710,382. Magnetic amplifiers. SPERRY CORPORATION. Feb. 22. 1952 [Feb. 28, 1951], No. 4771/52. Class 40 (4) [Also in Group XXXVIII] A magnetic amplifier responsive to an A.C. control signal comprises a pair of saturable reactors each having two load windings and a common control winding, the load windings being connected in series with individual half-wave rectifiers. As shown in Fig. 1, load windings 14-17 are arranged on the outer limbs of reactor cores 1, 2 which have a control winding 13 common to the centre limbs. The load windings are connected in pairs to separate loads 28, 35 Fig. 2, with their individual rectifiers 24, 29 and 31, 36 oppositely directed so that successive half cycles of current from an A.C. supply 20 alternate between the windings of a pair. Further rectifiers 27, 30 and 34, 37 are included in the load circuits so that unidirectional currents flow in the two loads. These currents are normally equal and act differentially in the loads which may constitute, for example, motor field windings, so that the resultant output is zero. If, however, an A.C. signal derived from the same supply is applied to winding 13, the inductances of the two windings on each core change in opposite respects, the direction of the change being determined by the in phase or antiphase relationship of the load and signal currents. Windings in which the inductances change in the same respect form the pairs of windings controlling each load so that a corresponding variation occurs in the unidirectional load currents and a resultant D.C. output is obtained. In an application to a follow-up system, Fig. 3, the amplifier 49 has its control winding 13 energized by the error signal from a selsyn system which comprises a transmitter 40 having its rotor 41 coupled to a two-phase motor 43, and a receiver 47 in which either the rotor 48 or the stator 46 is displaceable. The loads 50, 51 of the amplifier constitute differential control windings of a cascaded amplifier 52 which has two pairs of load windings 54, 55 and 59, 60 energized from a centre-tapped transformer 53, each pair of load windings having oppositely-directed series rectifiers 56, 57 and 61, 62. The core arrangements of the two amplifiers may be similar. The load windings of amplifier 52 act differentially in response to a resultant control signal in windings 50, 51 and cause an A.C. output to be applied to a tuned phase winding 63 of motor 43 over the transformer centre-tap, the phase relation of the output and the consequent direction of rotation of the motor being determined by the phase of the error signal. Damping of the system is effected by a rate signal from a speed-voltage generator 66, the rate and error signals being adjustably combined at a potentiometer 70. In a second embodiment, Fig. 5, the amplifier provides an A.C. output in response to an A.C. control signal. Two reactor cores, each carrying two load windings, are used as in the previous embodiment. The two windings on each core 83, 84 and 85, 86, however, are connected in parallel with their series rectifiers 81, 88 and 93, 94 oppositely directed. Each pair of windings has a series-connected load 99, 100 which are connected in opposition so that an output voltage across the two loads is normally zero. An A.C. control signal however causes the impedances of windings 83, 84 and 85, 86 to change in opposite respects so that the current in one load predominates and a resultant A.C. output is produced having its phase directly related to the phase of the control signal. A further embodiment, Fig. 7, uses the arrangement of cores and windings shown in Fig. 1. Each load winding 103-106 and its associated half-wave rectifier 108-111 however comprises the arms of a bridge-like circuit which has two loads 119, 120 connected across one diagonal and a centre-tapped A.C. supply 112 connected to the other diagonal and to the common point between the loads. Both loads carry full-wave rectified currents acting in opposite directions from the common point, one of these currents predominating when an A.C. signal is applied to the control winding.