Patent GB-879800-A (GB)
Title: Improvements in or relating to magnetic amplifiers
Inventor: FRANKLIN ERNEST
IPC: H03F9/02
Filed: 1958-06-04
Abstract: 879,800. Magnetic amplifiers. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. May 25, 1959 [June 4, 1958], No. 17924/58. Class 40 (9). Stages other than the first of a cascade magnetic amplifier have main and auxiliary cores, spaced alternating power pulses being applied to both cores interleaved by spaced alternating push-pull input pulses which induce no net voltage in the power circuit, an A.C. reset flux being applied to the auxiliary core the crests of which are suppressed in coincidence with the input pulses and the zero-point inflexions of which coincide with or closely follow the power pulses. The first stage shown in Fig. 1 also comprises main and auxiliary cores 1 and 2 with a slowly varying reversible D.C. input to windings 3 and 4 and an alternating pulse power supply to winding 5 of the main core 1 with the waveform shown in Fig. 2. Series-connected windings 6 and 7 on cores 1 and 2 are energized by A.C. the zero-point inflexions of which coincide with or closely pursue the power pulses and the amplitude of which is such as will switch core 1 half the length of its hysteresis loop. Application of the A.C. to core 2 as well as core 1 ensures that there is no net coupling with the input windings 3 and 4. In the absence of an input signal a power pulse of one polarity in winding 5 fires core 1 of the first stage and the subsequent half-cycle of A.C. in winding 6 sets the core to the centre of its loop ; the next power pulse is of opposite polarity and fires core 1 the other way while the next half-cycle of A.C. in winding 6 sets the core back to the centre of the loop, and so on. When an imput is applied the core is set off centre and the firing angles increase and decrease to complementary extents with respect to the power pulses of one polarity and the other. High impedance in the power circuit is presented to slowing varying flux changes between power pulses by the resistor capacitor combination. In the second stage, alternating power pulses in winding 10, each of which follows in quadrature a like polarity signal pulse in winding 3, fire core 1, at angles determined by the extent to which the core is set by the output of winding 5 in the first stage. The auxiliary cores 2 of the second stage has a winding 12 energized by a reset waveform which is such that winding 12 is momentarily de-energized at the crest of an A.C. waveform so as to allow input to windings 3 and 4 to set both cores 1 and 2 thus producing equal and opposite voltages in series-connected power windings 10 and 11. Winding 12 is then re-energized to set core 2 to saturation in a direction such that the next power pulse in winding 11 meets low impedance, and is then saturated in reverse before the next oppositely poled input pulse is received in winding 4. By this means the power pulse circuit is decoupled from the input circuit. Discharge of capacitor 13 in the power circuit is made slow enough so as not to overcome the coercive force of the cores. Further stages take the form of stage 12 and may use cores of increasing weight. The last stage may energize a balanced bridge to give a reversible D.C. output. The power pulses and the gapped A.C. wavetrains may be generated by the circuit of Fig. 5 in which A.C. switches the saturable cores associated with windings 21 and 22, pulses being picked off by winding 25. By connecting the pulse output in opposition to the A.C. over a linear transformer 29 the gapped A.C. is generated. Specification 798,416 is referred to.