Patent GB-753307-A (GB)
Title: Improvements in or relating to amplifier arrangements
Inventor: BARR JOHN DENZIL
IPC: G05F1/325
Filed: 1952-10-24
Abstract: 753,307. Electric control systems. SPERRY GYROSCOPE CO., Ltd. Oct. 9, 1953 [Oct. 24, 1952], No. 26743/52. Class 40(1) [Also in Group XXXV] In an amplifier system, e.g. for a servo - system, in which an A.C. feedback signal comprising a predetermined time function of the amplifier output is derived by resistive and inductive elements from the amplifier D.C. output, if the output is A.C., from a D.C. derived from this A.C. output, this D.C. is fed to a magnetic modulator to produce a modulated A.C. feedback signal with a carrier frequency equal to that of the amplifier input and having a magnitude and phase sense corresponding to the magnitude and polarity of the D.C. signal. Both resistive and inductive elements are windings on the modulator, and the time function preferably includes the first integral and differential of the amplifier output First embodiment, Fig. 1. As shown, the usual A.C. error signal is applied to the input 11-12 of an amplifier A, the D.C. output of which, corresponding in magnitude and polarity to the magnitude and phase sense of the error signal, is fed to the servomotor M in series with the control windings 1, 1<SP>1</SP> of a magnetic modulator 15. The windings 1-1<SP>1</SP> mounted on the outer limbs 17, 18 of the core 16 produce opposing fluxes # 1 , #<SP>1</SP> 1 , in the centre limb 19. Series connected excitation and slug windings 2-2<SP>1</SP> on the outer limbs are energized over a transformer 3 at the carrier frequency to produce opposed fluxes # 2 , # 2 <SP>1</SP>, in the centre limb 19, the slug action causing the fluxes in the outer limbs to vary according to the integral of the D.C. control current. The modulator output coil 4 carries a D.C. bias derived from a high impedance source over a resistor 5 which biases the outer limbs to non-linear parts of their magnetization curves. The difference in the A.C. fluxes in the outer limbs is arranged to be proportional to the difference in their permeabilities and is equal to the A.C. flux in the centre limb which induces an A.C. signal in the output winding 4 of carrier frequency modulated according to the integral of the D.C. control current. The out-' put winding 4 also functions as the secondary of the transformer injecting the error signal into the amplifier A, the primary 6 in this case also being provided on the centre limb of the core 16. Second embodiment; Fig. 2. To add an integral component of the error signal to the motor control circuit, the inverse, i.e. the first derivative component, is added to the negative feed back circuit by using a transformer in lieu of a differentiating network and combining it with the magnetic modulator. A coil 26 on an E-shaped core 21 is excited from a low impedance source at carrier frequency, and a slug winding 27 is wound round the three cores 21-22-23 such that equal magnetizing forces at carrier frequency are exerted on the cores 22-23 which are biased by the output and D.C. bias windings 24, 25, to non-linear parts of their magnetization curves. The windings are energized so that when the carrier frequency flux assists the biasing flux in one core 22-23 the corresponding fluxes are opposed in the other core. The core material and bias flux are chosen so that the resultant output voltage produced by the series differentially connected coils 24-25 is proportional to the current in the slug winding. The amplifier output is series connected with the motor M and a control winding 28 the current in which determines slug winding current and therefore the carrier frequency output of windings 24-25. The transfer function relating carrier output to D.C. control current is, as shown in the. Specification, such that the output contains both integral and differential components of the error signal. As in the Fig. 1 embodiment, the device may be used as the input transformer for applying the error signal to the amplifier by providing primary windings 29-30 on the cores 22-23.