Patent GB-802412-A (GB)
Title: Improvements in or relating to memory elements for control systems
IPC: H03K3/45
Filed: 1956-12-05
Abstract: 802,412. Magnetic amplifiers. WESTING- HOUSE ELECTRIC INTERNATIONAL CO. Dec. 5, 1956 [Dec. 15, 1955], No. 37152/56. Class 40 (9). Magnetic cores 10, 11 energized alternately from an alternating supply 16 are arranged to provide a continuous train of unidirectional output current pulses comprising positive halfcycles of the A.C. supply, the output pulses having two possible phase positions commencing at 0 or # radians, as shown in Fig. 2, which are obtained by applying a temporarily-acting D.C. or A.C. control signal to one or the other of control terminals 49, 54. The arrangement includes an additional core 57 in which the state of the circuit is stored magnetically so that if the power supply fails, the circuit supplies an output in the same phase position when the supply is restored. The cores 10, 11 have output windings 13, 15 which are alternately energized from a centre-tapped transformer secondary winding 21 over rectifiers 24, 29 and supply a common output lead 26. Reset windings 12, 14 are also associated with the cores, each winding being connected in series with an individual rectifier gate 37, 42 which is opened in alternate half-cycle supply periods by the application of rectified outputs of a centre-tapped transformer winding over resistors 38, 43. The first complete cycle of alternating current in winding 21 drives both cores to positive saturation and no output is obtained. The next halfcycle causes one saturated core, e.g. core 10, to pass an output current to lead 26. A feedback current is also obtained which passes through reset winding 14 and an opened rectifier gate 37 and negatively saturates core 11. No output current flows during the following half-cycle as this is utilized to drive core 11 from negative to positive saturation. As no feedback current is available for reset winding 12 although its rectifier gate 42 is open at this stage, core 10 remains at positive saturation and its output winding passes output current in succeeding alternate half-cycles. The output may be transferred to winding 15 on core 11 and its phase displaced by # radians as a result, by applying a temporary A.C. or D.C. control signal to terminal S4 of such polarity that it inhibits the passage of feedback current to reset winding 14 during a half-cycle period of output current. Core 11 remains at positive saturation so that it takes over the output current and feedback is established through reset winding 12 which inhibits core 10. The converse effect is obtained by a control signal at terminal 49. The additional magnetic core 57 has two windings 58, 59 which magnetize the core to saturation in one direction or the other when the associated output winding 13 or 15 is non- conducting. If the power supply fails, the direction of remanent magnetism of core 57 records the state of the circuit. When the power supply is restored the circuit resumes its output in the same phase position, as the winding 58 or 59 which previously carried current provides a short-circuit path for feedback current which would otherwise reverse the circuit state by driving the originally conductive core 10, 11 to negative saturation.