GB786385A - Improvements in or relating to magnetic amplifier apparatus - Google Patents

Abstract

786,385. Magnetic amplifiers. WESTING- HOUSE ELECTRIC INTERNATIONAL CO. Aug. 4, 1955 [Aug. 9, 1954], No. 22406/55. Class 40 (4). A linear input-output characteristic which gives a zero output for a zero input is obtained with a magnetic amplifier by applying the output of the amplifier to a transformer, the quiescent output of the amplifier being sufficient to ensure that the transformer works on the linear portion of its input-output characteristic, the output of the transformer being applied to a rectifier having a threshold voltage and the output of the transformer when energized by the amplifier quiescent output being just sufficient to equal the threshold voltage of the rectifier. In the illustrated embodiment, D.C. in a circuit supplying a load 3 from a source 2 is shunted from a resistor 15 through control windings 9 and 11 of transductor elements 6 and 7. Windings 17 and 19 of the elements are energized by A.C. from a source 20 which also supplies bias windings 23, 25, with rectified current. Output current in the A.C. windings 17, 19 flows through primary 35 of transformer 33 which is such that, as shown in Fig. 3, the quiescent current Ig in the A.C. windings holds the transformer at a point A on the linear part of its characteristic to produce a voltage Et equal to the threshold voltage of a barrier layer type rectifier 41 connected to the secondary winding 36 of the transformer. Assuming that the bias windings are not energized the output from rectifier 41 is zero when the input to control windings 9 and 11 is zero and these quantities are linearly related. If the bias windings are energized the rectifier 41 has a define output when the input to control windings 9 and 11 is zero, the output being reduced or increased depending on the sign of the input D.C. signal. This enables a D.C. meter 43 to be used with a centre-zero scale. A filter network may be. used to smooth the output of rectifier 41 and the core of transformer 33 may be constructed of a material having a substantially rectangular magnetic hysteresis loop.