US2753517A - Combination control and reference circuit for a magnetic amplifier - Google Patents

Description

July 3, 1956 E. T. HOOPER, JR 2,753,517 COMBINATION CONTROL AND REFERENCE CIRCUIT FOR A MAGNETIC AMPLIFIER Filed March 27, 1953 7O CONTROL 68 SIGNAL VA\ A -7a -4e; '86 INVENTOR 92 $90 EDWARD T HOOPER,JR. A A I- 96 v 94 BY RN, Hfl QkQ ATTORNEYS COMBINATION CONTRGL AND REFERENCE CIRCUIT FOR A MAGNETIC AMPLIFIER Edward T. Hooper, Jr., Hyattsville, Md., assignor to the United States of America as represented by the Secre= tary of the Navy Application March 27, 1953, Serial No. 345,271

7 Claims. (Cl. 323--89) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to magnetic amplifiers and more particularly pertains to a combination bias and control circuit therefor.

In magnetic amplifiers, the reactance of the cores and hence the current flow through the controlled windings thereon is varied by the passage of a control current through the control winding on the core. The proper operating flux level in the cores is established by bias circuits, which bias circuits commonly utilize separate bias windings on the cores which are energized from the power supply source.

in half-wave self-saturating magnetic amplifiers it is desirable to utilize half-wave currents for both biasing and control. The present invention is a continuation-inpart of the copending application of Edward T. Hooper, Serial No. 335,619, filed February 6, 1953, for Full-Wave Magnetic Amplifier. The control circuit provides a halfwave reference voltage from an A. C. supply source, and a half-wave control voltage from an A. C. control source, both control and reference voltages being placed on the saturable reactor core in a single winding.

An important object of this invention is to provide a circuit for applying half-wave control and reference voltages in a single winding on the reactor core.

Another object of this invention is to provide a circuit for providing a half-wave reference from an A. C. supply source and a half-wave control voltage from an A. C. control source and for applying the control and reference voltages to a single winding on the reactor.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a schematic diagram of the combination reference and control circuit applied to the bridge type halfwave magnetic amplifier; and

Fig. 2 is a schematic diagram of a modified form of combination bias and control circuit having a second amplifier stage connected in cascade therewith.

Reference is now made more specifically to Fig. l of the drawings wherein there is illustrated a half-wave bridge type magnetic amplifier having a combination bias and control circuit applied thereto. The amplifier includes a pair of cores 10 and 12 of saturable magnetic material. The core 10 has split load windings 14 and 16 thereon, the core 12 having split load windings 18 and 2d wound therein. Load windings 14 and 18 are connected in series circuit with rectifiers 22 and 24 across the A. C. supply source 26 and constitute one pair of adjacent legs of a bridge circuit, the load windings 16 and 20 being connected in series circuit with rectifiers 28 and 30 across the supply source 26 and forming the other pair of adjacent legs of the bridge circuit. The load 32 is connected nited States Patent C 'ice to a point between the rectifiers 22 and 24, and between the rectifiers 28 and 30.

The circuit thus far described is conventional, and forms no part of this invention. In operation, during onehalf cycle of the A. C. power supply voltage 26, current flows through winding 14, rectifier 22, and in one direction through load 32, through rectifier 28, and winding 16, the load current also flowing during the same half cycle through winding 20, rectifier 30, through load 32 in the opposite direction, through rectifier 24 and winding 18. The parameters of the circuit are adjusted so that when the reactances of the cores it) and 12 are equal, the load currents flowing through the load windings on each of the cores are equal, and consequently the resultant current flowing through the load 32 is zero. However, when the reactances of the cores are varied differentially, a resultant load current flows through load 32 in a direction dependent upon the sense of the unbalance of the cores.

The combination bias and control circuit includes a transformer 34, the primary 36 of which is connected across the A. C. power supply source 26. The transformer 34 has a center-tapped secondary 38, which center-tapped secondary constitutes one pair of adjacent legs of the control bridge circuit. The third leg of the control bridge circuit includes resistor it), rectifier 42, and corn trol winding on the core 12. The fourth leg of the bridge includes resistor 46, rectifier 5t and control winding 52 on the core 10. A balancing potentiometer 46 may be provided to facilitate equalizing the current flow through the control windings 44 and 52 under zero control signal conditions. The control signal source 54 is connected between the tap on the secondary 38 and the tap on the potentiometer 46. Rectifiers 42 and 50 are polarized so that current flows through the control windings 4-4 and 52 during the non-conducting half cycle of the half-wave bridge circuit comprising windings 14, it 18 and 26 previously described. Resistors 4t) and 48 and potentiometer 46 are adjusted so that the half-wave currents flowing through windings 44 and 52 preset the desired operating flux level in the cores 10 and 12. When a control signal from the control source 54 is applied, the combination reference and control circuit bridge is unbalanced causing an increase in current flow through one of the control windings and a decrease in current flow through the other control winding. These combined actions take place on the half-cycle when the load windings on the cores 1t) and 12 are non-conducting, whereby the flux levels of the respective cores are preset to the proper value determined by the control signal to thereby determine the firing angle of the cores on the succeeding half-cycle.

As is deemed apparent, the combination control and reference bridge circuit provides a half-wave reference current from the A.- C. power supply source, and in addition effects half-wave control from an A. C. control source.

In the embodiment illustrated in Fig. 2 of the drawings, the combination control and reference circuit includes a center-tapped impedance having legs 60 and 62, which impedance may be the inductance illustrated or, alternatively, may comprise a capacitive or resistive impedance. The legs 60 and 62 of the center-tapped inductance form one pair of adjacent legs of a bridge circuit, rectifiers 64 and 66, resistors 63 and 70, windings 72 and 74 on saturable reactor cores 76 and 78 respectively and the potentiometer 80 forming the other pair of adjacent legs of the bridge circuit. Potential from the A. C. power supply source 82 is applied across the legs 60 and 62 of the center-tapped inductance, and the rectifiers 6 and 66 are phased so as to allow current flow through the control windings 72 and 74 of the bridge only in one to a point direction. This permits a constant half-wave reference voltage to be applied to the control windings, which voltage is adjusted to the proper value by the resistors 68 and 70. The control signal from the source 84 is applied between the tap on the center-tapped impedance and the tap on the potentiometer 89, the potentiometer being. provided to permit balancing of the bridge circuit under zero control signal conditions. When the bridge is balanced, the same reference voltage appears on both control windings 72 and '74. The application of a control signal, however, unbalances the bridge circuit, raising the voltage on one control winding and lowering the voltage on the other.

Load windings 86 and 88 on cores '76 and 78 respectively are connected in a bridge circuit, and form one pair of adjacent legs thereof. The remaining pair of legs of the bridge are formed by rectifiers S t) and 92 and the control windings 94 and 96 on the cores 95 and 100, which last mentioned pair of cores constitute a portion of a second stage of the magnetic amplifier. Load windings as and 3% are energized, as from the supply source 82 and the rectifiers 9t) and 92 are phased so that load current flows through the load windings during the half-cycle of the power supply voltage succeeding that half-cycle during which reference flux is established in the cores 76 and 78. The second stage load circuit [not illustrated] may be of any desired type such as the half-wave bridge type illus trated in connection with Fig. l of the drawings.

From the foregoing it is deemed apparent that the combination bias and control circuit supplies both a halfwave reference voltage and a half-wave control voltage to a single control winding on each of the reactors. The half-wave reference potential may be supplied from an A. C. power supply source and the control voltage supplied by either an A. C. or a D. C. control source.

The voltages induced in the control windings on each of the cores are additive and only under zero control signal conditions will there be no induced current flow through the control signal source. With a control signal, an unbalance occurs and a small induced current flows through the control source. This is true of all two-core control systems, but in the instant case the induced current does not flow on the half-cycle during which control is being formed, and no error results.

It is deemed apparent that the A. C. control signal source and the A. C. supply source may be interchanged in the control bridge circuit provided one of the rectifiers in the control bridge circuit is reversed so that the reference or bias current only flows during one half-cycle of the A. C. supply voltage. However. the bridge circuit including power windings 14, i5, and Eli must be energized from a power supply source. Thus, the power supply voltage as from source 2 6 may he applied between the tap on transformer secondary winding 32 and the tap on potentiometer 46, in which case the control voltage from source 54 would be applied across transformer primary winding 36. However, one of the rectifiers such as 42 must be reversed so that the reference or bias current llows during one half-cycle of the power supply voltage.

Obviously many modifications and variations of the present invention are possible in the light of the a oof/e teachings. it is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent is:

l. in a half-wave self-saturating type magnetic amplifier including a pair of saturable reactor cores each having controlled winding means energized from an A. C. source on the same alternate half-cycles of said source. a combined bridge type bias and control circuit including a control winding for each of said cores interconnected to be included in one pair of adjacent legs of the bridge, impedance elements serially interconnected with said control winding to form the other pair of adjacent legs of 4 the bridge, circuit means for applying said A. C. source across one pair of diagonally opposite terminals of the bridge, unidirectional impedance elements in said bridge circuit for passing current from said source in one direction only through the bridge so that half wave current flows through the control windings only during the other alternate half-cycles'of said source, and means for applying a control signal across the other pair of diagonally opposite terminals of the bridge to thereby differentially vary the half-cycle current flow through the control windings.

2. In a half-wave magnetic amplifier, a pair of cores of magnetic material having definite saturation characteristics, a control winding; on' each of said cores, a control signal source, means connecting said control windings to said control source in separate parallel branch circuits, an impedance element in each of said branch circuits, supply voltage means for applying an A. C. potential across said impedance elements, and unidirectional impedance elements in each of said branch circuits connected so that current from said supply voltage means flows in the same direction through said branch circuits only during the same alternate half-cycles of the supply voltage means.

3. The combination of claim 2 including means in each of said branch circuits for adjusting the magnitude of the half-wave currents flowing therethrough.

4. A bridge circuit energized from a biasing source and a control signal source. for functioning simultaneously as a bias circuit and a control. circuit for a magnetic amplifier having a plurality of saturable core reactors with power windings wound thereon, saidbridge circuit being defined by a closed series loop including control windings for presetting, the flux levels in predetermined ones of said reactors in a manner'correlative to the current flowing through said control windings as a consequence of application thereto of a biasing voltage and a control voltage from said biasing source and said control signal source, respectively, and unidirectional conductive means for permitting current flow through said series loop in one direction only.

5. The bridge circuit of claim 4, wherein said bridge has two pairs ofdiagonally opposite terminals, and further including circuit connections for. connecting said control signal source across one of saidpairs of diagonally opposite terminals, and circuitv means for applying biasing voltage from said biasing: source across the other pair of diagonally opposite. terminals.

6. A bridge: circuit according to: claim 5 to serve as a common bias and control circuit for a half-Wave magnetic amplifier having a pair of saturable core reactors with power windings arranged to be energized only on the same alternate half-cycles from. an A. C. source, wherein said. unidirectional conductive means are so poled that said current flow through said series loop occurs only during the nonconductive half-cycles of said power windmgs.

7. A half-wave magnetic amplifier having a common bias and control circuit comprising, in combination, a source of alternating current; a pair of saturable core reactors; load windings on said reactors connected across said source through rectifier means arranged to-pass current. through said load windings only during the same alternate half-cycles of said source; a control winding on each of said cores and serially interconnected to define a first common terminal at the junction thereof; a pair of impedances' serially interconnected to define a second common. terminal at the junction thereof; a first unilateralv conductive device electrically interposed between one' of said. control windings and one of said impedances and serially connected to the unconnected terminals of said one control winding and said one impedance, and a second unilateral conductive device elec trically interposed between the other of said control windings and the other of saidirnpedances and serially con nected to the unconnected terminals of said other control winding and said other impedance to thereby form a direction through said series loop only during the nonclosed series loop including said pairs of control Windconductive half-cycles of said load windings.

ings and impedances, and said first and second unilateral conductive devices; a control signal source connected References Cited in the file of this patent across said first and second common terminals; and cir- 5 UNITED STATES PATENTS cu1t means for applying an alternating current from said alternating current source across said pair of impedances, 2,632,145 Sikorra Mar. 17, 1953 said unilateral conductive devices being poled so as to 2,677,099 Rau Apr. 27, 1954 pass current from said alternating current source in one 2,704,823 Storm Mar. 22, 1955

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