Elektromagnetische Betaetigungsvorrichtung mit Rueckkopplung

841,199. Magnetic amplifiers. SPERRY RAND CORPORATION. Sept. 10, 1956 [Sept. 26, 1955], No. 27633/56. Class 40 (9). [Also in Group XL (c)] In a circuit for operating an electromechanical device such as a relay 10, a signal 14 is applied to an amplifier 13 energized from a source of variable potential V, to produce a flux in the magnetic core 10, a coupling circuit 12 being provided to apply feed-back to the amplifier. The amplifier 13 may include thermionic discharge tubes of the high vacuum or gas type, transistors (see Group XL (c)), or a magnetic amplifier and a further feed-back may be effected over resistor R 1 . While the flux is building up in core 10 a voltage is generated in coil 12 and is effective to increase the drive applied to the amplifier 13. As soon as a steady state has been reached the feed-back decreases so that the holding current of the relay is less than the initial actuating current. The relay may be held operated over an auxiliary contact. To prevent a negative-going signal being fed back to the amplifier 13 due to the fall in flux from the actuating to holding valve, a diode may be included in the feed-back path, Fig. 2 (not shown). When the circuit is operated without a diode in the feed-back path the decrease in flux may be such as to generate a sufficiently large voltage in coil 12 for the amplifier to provide insufficient current to keep the relay 10 operated so that it releases and the cycle subsequently commences again. In a modification, Fig. 4, the input signal is applied at terminal 50 to windings 44, 45 on magnetic cores 40, 41, energized from an A.C. supply over diodes D 3 , D 4 . The output from windings 42, 43 is applied to a winding 48 on a device such as a relay having a magnetic core 49. A feed-back voltage is generated across coil 51 and applied over a diode to the input circuit. As an alternative arrangement a further winding may be added to each of the cores 40, 41 to which the voltage from the feed-back winding 51 is applied.