Patent GB-782032-A (GB)
Title: Improvements relating to magnetic amplifiers
IPC: H03F9/04
Filed: 1955-06-01
Abstract: 782,032. Magnetic amplifiers. SPERRY CORPORATION. June 1, 1955 [June 9, 1954; June 9, 1954], No. 15768/55. Class 40 (4). Undesired voltages which are induced in the control circuit of a magnetic amplifier responsive to alternating current control signals are neutralized by an opposing potential of the same waveform obtained from the load current circuit. Two groups of embodiments, Figs. 5 to 14, and Figs. 23 to 28, are described, relating to self-excited push-pull and single amplifiers respectively. Push-pull amplifiers. The currents in individual loads differ, or a resultant current in a common load exists, only during the interval between core saturation of one transductor comprising the push-pull amplifier and saturation of the other transductor, this interval being determined by the magnitude of the A.C. control signal. As the core conditions of the transductors are dissimilar during this interval, a. resultant undesired voltage is induced into the control windings by current in the main windings. This undesired voltage corresponds to the difference in the main winding currents, and is neutralized by a potential developed from these currents and applied in opposition in the control winding circuit. As shown in Fig. 5, the push-pull amplifier may comprise a pair of auto-self-excited parallel transductors with main windings A, B, C, D supplying separate loads ZL. A transformer 25 has a centre-tapped primary winding 26 shunted by a resistor 24 and is connected in the power supply circuit in such a way that, when the currents through the two transductors differ, a neutralizing voltage is established by secondary winding 27 in the control circuit. Auto - self - excited bridge rectifying transductors may alternatively be used, Fig. 6, in association with a neutralizing potential arrangement comprising a centre-tapped resistor 37 and a transformer 36, as shown, or with any of the transformer-resistance combinations illustrated in Figs. 6a to 6c substituted at X. In a modification, Fig. 13, the neutralizing potential is derived directly from separate resistors R1, R2 respectively in series with the two transductors. By providing an adjustable shunting potentiometer P, Fig. 13a, the amplitude of the neutralizing potential is adjustable. The resistors may be associated with separate transformers T1, T2 arranged as shown in Fig. 14. Alternatively this Figure may be modified by any of the transformer-resistance combinations shown in Figs. 14a to 14c. Two auto-selfexcited transductors may also be associated with a centre-tapped A.C. supply and a common load ZL, in which case the neutralizing potential is derived directly from the load by way of an adjustable potentiometer P, Fig. 8, or a shunting transformer, Fig. 9 (not shown). The same methods of deriving the neutralizing voltage are employed when the transductor circuits in Fig. 8 and 9 are modified by the addition of cross-connected auto-self-excitation windings A<SP>1</SP>-D<SP>1</SP>, Fig. 10 and Fig. 11 (not shown), these additional windings being separately associated with the main windings in the order A-A<SP>1</SP>, B-B<SP>1</SP>, &c. In a further auto-self-excited amplifier, Figs. 7 and 12, the two main windings of each transductor are connected to opposite sides of a centre-tapped A.C. supply and separate loads ZLA, ZLB are provided. The supply is obtained, in Fig. 7, from a centretapped transformer 40, and the neutralizing voltage is applied in the control circuit by two transformers 55, 56 having primary windings 51 to 54, each shunting a resistor 43, 45, 47, 49 in series with a main winding. A single transformer is used in Fig. 12 with a resistance R in the control circuit and separate primary windings T for each main winding. The use of bias windings (shown in several of the Figures) and further control windings is mentioned. It is also suggested that separate self-excitation windings supplied by load current over rectifiers may be employed in place of auto-self-excitation, and that further elements may be provided for rectifying the output current, Figs. 16, 17, 19 and 20 (not shown). Single amplifiers. The basic transductor controlled by A.C. signals may be either selfexcited over a separate winding or auto-selfexcited. During the interval between commencement of a half-cycle of alternating current (magnetizing current) and saturation of a transductor core by this current, an undesired voltage is induced in the control winding. This voltage is neutralized by (a) applying an opposing voltage corresponding in waveform to the alternating supply and (b) opposing the resulting waveform by a voltage obtained from the load. One arrangement is shown in Fig. 23, in which an auto-self-excited transductor has its control windings connected in series with secondary windings of transformers T1, T2. The primary windings are respectively connected across the A.C. supply V and the load ZL to supply inhibiting voltages acting as specified in (a) and (b) above. A variable potentiometer may be substituted for transformer T2, Fig. 25 (not shown). In the case of an auto-self-excited bridge rectifying transductor, Fig. 27, transformer T2 is connected across a resistor P in series with the transductor. In a modification, Fig. 26 (not shown), the transformer T2 is omitted so that resistor P carries the control signal as well as the load current. Fig. 28 illustrates an auto-self-excited full-wave rectifying transductor in which transformer T1 additionally provides the centre-tapped supply necessary for the transductor main winding circuit, while transformer T2 has separate primary windings, one in each main winding circuit. When the nature of the load is not wholly resistive, impedance giving the required waveform characteristics should be substituted for the resistors P.