Patent GB-1098904-A (GB)
Title: Improvements in or relating to magnetic amplifiers
IPC: H03K19/16
Filed: 1963-12-31
Abstract: 1,098,904. Magnetic amplifiers. G.E.C. ROAD SIGNALS Ltd., P. J. BARKER, E. GARDNER and S. D. POOL. Dec. 22, 1964 [Dec. 31, 1963], No. 51371/63. Heading H3B. The magnetic amplifier of the second harmonic type described in Specification 1,098,903, has the centre limb of the three-limbed core 2, Fig. 3, divided into two control legs 9, each leg having a control winding 7 both of which must be energized simultaneously for a control flux to influence the coupling between the input and output windings 5A, 5B and 6A, 6B. Each control leg has a short-circuited turn 8, which influences the threshold level at which the lesser of two control signals applied to respective control windings causes an effective output to be produced. If one control signal is small or absent, the flux due to the other control winding remains in the centre limb and no output is produced in the secondary winding. As described in the Specification referred to, the primary and secondary windings are wound in output-cancelling relationship on the threelimbed core and an associated two-limbed core 1, Figs. 1 and 4 (not shown). In a modification, a feedback winding is provided in one or both of the control legs. In one application, Fig. 5, a bi-stable circuit comprises two magnetic amplifiers 13, 14 each with its own control and output circuit, the control and feedback circuit of each amplifier coupling with both control legs and with one leg of the other amplifier. The input windings are not shown. In operation, energization of any one control circuit by a pulse causes that magnetic amplifier to produce an output and at the same time provide a flux in one control leg of the other amplifier which inhibits a second output. These conditions are maintained by the feedback circuit after the control pulse terminates. If a pulse is subsequently applied to the control circuit of the second amplifier, the change in control leg fluxes in both amplifiers is sufficient to transfer the output condition from the first to the second amplifier. A modified circuit, Fig. 6 (not shown), has a continuously energized control winding on one amplifier 26 which is coupled only to the control legs of that amplifier, in which case the arrangement operates as a monostable circuit and produces an output from amplifier 26 except for the duration of a control signal appled to the second amplifier 25. A " stick circuit " is described, Fig. 7 (not shown), in which an amplifier has the feedback winding 23 on one control leg only and short-circuited windings 26, 35, 36 encircle the control legs both individually and collectively. An output is obtained when both control windings 21, 22 are energized. If the control input to control winding 21 is removed, the output condition of the amplifier is maintained by the feedback winding. An application of the Fig. 7 embodiment is described, Fig. 8 (not shown), in which a normal output is applied to loads B from a Fig. 7 amplifier 29 through a Fig. 6 monostable circuit. When the control winding 21 is pulse energized through a switch 40 and with control winding 22 energized through switch 41, the monostable circuit 34 is switched and loads A become energized. If the power supply fails then loads B are energized on its recommencement.