US2229952A - Magnetic amplifier - Google Patents

Magnetic amplifier Download PDF

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Publication number
US2229952A
US2229952A US235862A US23586238A US2229952A US 2229952 A US2229952 A US 2229952A US 235862 A US235862 A US 235862A US 23586238 A US23586238 A US 23586238A US 2229952 A US2229952 A US 2229952A
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US
United States
Prior art keywords
current
core
windings
control winding
branch circuits
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US235862A
Inventor
Austyn L Whiteley
Leslie C Ludbrook
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General Electric Co
Original Assignee
General Electric Co
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Filing date
Publication date
Priority to US118914A priority Critical patent/US2169093A/en
Priority to GB17191/38A priority patent/GB514865A/en
Application filed by General Electric Co filed Critical General Electric Co
Application granted granted Critical
Publication of US2229952A publication Critical patent/US2229952A/en
Anticipated expiration legal-status Critical
Application status is Expired - Lifetime legal-status Critical

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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00Silicon; Compounds thereof
    • C01B33/20Silicates
    • C01B33/36Silicates having base-exchange properties but not having molecular sieve properties
    • C01B33/46Amorphous silicates, e.g. so-called "amorphous zeolites"
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03FAMPLIFIERS
    • H03F9/00Magnetic amplifiers
    • H03F9/02Magnetic amplifiers current-controlled, i.e. the load current flowing in both directions through a main coil
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03FAMPLIFIERS
    • H03F9/00Magnetic amplifiers
    • H03F9/04Magnetic amplifiers voltage-controlled, i.e. the load current flowing in only one direction through a main coil, e.g. Logan circuits
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F29/00Variable transformers or inductances not covered by group H01F21/00
    • H01F29/14Variable transformers or inductances not covered by group H01F21/00 with variable magnetic bias

Description

1941- A. L. WHITELEY EIAL I 2,229,952

MAGNETIC AMPLIFIER Filed Oct. 19. 1938 Fig.1. Fig.3.

IFIQA.

0.6. VGLTS.

REVERSE. FORWARD.

CURRENT D. C. VOLTS.

I I I l I I 1 REVERSE. FORWARD.

CURRENT IN COIL 2.

Fi g6.

VOLTS 0 N RELAY l0.

vozrs a/v RELAY m.

RELAY PICKUP VOLTS QC. VOLTS.

Inventors: Ausoyn L.Whiteley, v Leslie C. LudbTOOk,

by Han/1,7

RE VER$. FORWARD. T h e I A Attorn Patented Jan. 1941 h i UNITED STATES PATENT OFFICE MAGNETIC AMPLIFIER Austyn L. Whiteley and Leslie C. Ludbrook, Rugby, England, asslgnora to General Electric Company, a corporation oi New York Application October 19, 1938, Serial No. 235,862 In Great Britain June 9, 1938 6 Claims. (Cl. 171-242) This invention relates to magnetic amplifiers dlcated by the arrows marked on the core. Conand more particularly to devices of thiskind trol winding 2 is energized by a unidirectional which utilize the saturation of an iron core with current which may be varied in magnitude and unidirectional fiux. also aperiodically reversed in direction by any- 5 An object of the invention is to provide a satsuitable means, such as by a slide wire potenurable core reactor, the output characteristic of tiometer 6. which is dependent on the polarity of the uni- Connected in circuit with each of the condirectlonal saturating flux. trolled windings 3 are separate circuit elements Another object of-the invention is to provide S O by y Of p e as es stors. T e

10 a new and improved magnetic amplifier for prosum of the voltage drops a s t e resistors 1 l0 ducing a controllabl unidir ctional out ut pois impressed on a voltmetric electroresponsive detential which may be applied to the control elecvice 8 of any suitab e o Suc a an n y trodes of vacuum tubes, voltmeter or the control electrode of a vacuum A further objector the invention is to provide u a magnetic amplifier c ntrol system hi h con- The operation of Fig. 1 can best be understood 15 trols a pair of standard relays in such a way as y ef ce to g. 2 in which the sum of the to produce a control system which i th equivavoltage drops through the resistors 1 is plotted as lent of a sensitive polarized relay, a function of the current in the control wind- The invention will be better understood from ing AS w e e the voltage is a mum the following description taken in connection with when the control current is zero. As the control 20 the accompanying drawing and its scope will be current increases in what is labeled the forward pointed out in the appended claims. direction, that is to say, the direction which In the drawing, Fig, 1 i diagrammatic 11. causes the flux produced by the winding 2 to be lustratlon of an embodiment of the invention for in e e direction as t fluxes p ed y producing an amplified constant polarity output the windings 3, the core I Will e p d y at 2 potential. Fig. 2 illustrates the operating characurated due to the cumulative action of all of the teristic of Fig. 1, Fig. 3 is a modification in which windings, hu reducing t e reactance of the the amplified output potential reverses when th windings 3 and increasing the current in the repolarity of the unidirectional control current re- Sisters 7, thereby p y increasing t e age 3 verses, Fig. 4illustrates the operating characterisdrops across these resistors Thus, a iv ly tic of Fig 3, Fig, 5 illustrates diagrammatically small increase in current in the winding 2 in another modification for producing the effect of the forward direction will substantially saturate a polarized relay, Fig. 6 illustrates the operating the core so that further increases in current in characteristic of Fig. 5, and Fig. '7 shows a, modithis coil will produce relatively small increases 5 fled arrangement or the control winding. in voltage. If now the current in the coil 2 is Referring now tojhe drawing and more parreversed S0 as to make its fillX oppose the fluxes ticularly to Fig. 1, the core of the magnetic amof e w s 3 the a t g effect will be plifier is shown by way of example as a thr enegligible for relatively large changes in control legged core I provided ith a contr l winding 2 current, so that the sum of the voltages across 40 on the center leg and a pair of controlled windthe devices 7 is relaftlvely independent of es 4 ings 3 on the outer legs. These controlled windin control current m the reversed direction. 0 ings are connected across a suitable source of 8.1- It should, o course, be understood that the ternating current 4 in separate parallel branch Currents in the resistors 7 are out of time P e circuits, each of which contains aseparate asymso that when the current in'one resistor is a metrical conducting device 5 of any suitable form, maximum e u ent in t e other resistor is a such forexample, as a copper oxide rectifier, minimum. Consequently, the individual instan- The polarities or these asymmetrical conductors teneous v l a e drops across the resistors 1 do are oppositely arranged so that positive half not add erlthmetieelly- WeVer, they W add waves of current flow through one controlled almost arithmetically in a device having a rela- 60 winding and negative half .waves of current flow tively large time constant, such as a ballistic inthrough the other controlled winding. The construment. trolled windings are so arranged on the core that Fig. 2 may also be taken as representative of the pulsating unidirectional fluxes which they the instantaneous voltage drop across either one produce in the core are inithe same direction of the resistors l. with respect to the control winding 2, as is in- The principal reason that the output voltage registered on the device 8 increases so rapidly with changes in current in the forward direction in the coil 2 is that there is a regenerative or feed back effect which occurs when the current in the windings 3 increases because the increased flux which then results aids the saturating effect of the control winding 2.

Fig. 3 difiers from Fig. 2 in that the right hand asymmetrical conductor 5 has been reversed. Consequently, only positive (or negative) half waves of current from the source flow through the controlled windings. This change causes the fluxes produced by the controlled windings to be in opposite directions with respect to the control winding 2 and it also causes the polarities of the voltage drops across the resistors I to be opposite instead of the same, as in Fig. 1. Capacitors 9 are connected in parallel with resistors I so as to smooth out the voltage drop across the resistors I.

The operation of Fig. 3 will be clear from an inspection of Fig. 4. When no current flows in the control winding the voltage drops across the resistors l are equal and opposite so that there is no net voltage across the two. As the control current increases in the forward direction the current through one control winding and its serially connected resistor increases more rapidly than the current through the other control winding and its resistor so that the sum of the voltages increases with a given polarity. If now the control current is reversed the opposite effect is produced and the resultant voltage across the two resistors 1 increases with the opposite polarity. In this manner a reversible polarity unidirectional potential may be obtained and controlled by means of a relatively small unidirectional control current.

In Fig. 5 the resistors I have been replaced by windings l0 and I0 which, for example, may be considered the operating windings of conventional relays or contactors.

The operating characteristic of this circuit is shown in Fig. 6. Thus, when there is no current in the control coil 2 the voltage across both relay windings is below the drop out values of the relays so that both relays will be dropped out. If the current increases slightly in a forward direction the voltage across the relay l0 increases very rapidly and soon causes the relay I0 to pick up, Whereas the voltage across the relay l0 actually decreases slightly. Similarly, if the current through the control winding 2 increases slightly in the reverse direction the opposite efiect' takes place and the relay ill will drop out. In this manner an arrangement is produced which is the equivalent of a very sensitive polarized relay, although the actual relays which are employed are inexpensive and rugged standard non-polarized relays or contactors.

Instead of mounting the control winding on the center leg of the core it may be divided into two sections, each of which is wound on an outer.

leg, as shown in Fig. 7. This modification of the arrangement is equally applicable to Figs. 1, 3 and 5.

While there have been shown and described particular embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent or the United States is:

1. In combination, a core of magnetic material having a definite saturation characteristic, a control winding thereon, a pair of controlled windings thereon, a circuit for energizing said control winding with a selectively variable magnitude continuous current, a source of alternating current, said controlled windings being connected to said source of alternating current in parallel branch circuits, separate unidirectional conducting devices connected in each of said branch circuits so as to cause positive half waves of current to flow through one branch circuit and negative half waves of current to flow through the other branch circuit, said controlled windings being so arranged that the fluxes they produce in said core are in the same direction relative to said control winding, separate circuit elements connected in each of said branch circuits, and means responsive to the sum of the voltage drops across said elements.

2. In combination, a core of magnetic material having a definite saturation characteristic, 2. control winding thereon, a pair of controlled windings thereon, a circuit for energizing said control winding with continuous current the direction of which is selectively reversible, a source of alternating current, said controlled windings being connected to said source of alternating current in parallel branch circuits, separate unidirectional conducting devices connected in each of said branch circuits so as to cause positive half waves of current to flow through one branch circuit and negative half waves of current to flow through the other branch circuit, said controlled windings being so arranged that the fluxes they produce in said core are in the same direction relative to said control winding, separate circuit elements connected in each of said branch circuits, and means responsive to the sum of the voltage drops across said elements.

3. In combination, a core of magnetic material having a definite saturation characteristic, a control winding thereon, a pair of controlled windings thereon, a circuit for energizing said control winding with a selectively variable magnitude continuous current, a source of alternating current, said controlled windings being connected to said source of alternating current in parallel branch circuits, separate unidirectional conducting devices connected in each of said branch circuits so as to cause positive half waves of current from said source to flow through both of said branch circuits and to prevent the flow of negative half waves of current from said source through said branch circuits, said controlled windings being so arranged that the fluxes they produce in said core are in opposite directions relative to said control winding, separate circuit elements connected in each of said branch circuits, and means responsive to the sum of the voltage drops across said elements.

4. In combination, a core of magnetic material having a definite saturation characteristic, a control winding thereon, a pair of controlled windings thereon, a circuit for energizing said control winding with continuous current the direction of which is selectively reversible, a source of alternating current, said controlled winding being connected to said source of alternating current in parallel branch circuits, separate unidirectional conducting devices connected in each of said branch circuits so as to cause positive half waves of current from said source to flow through both of said branch circuits and to prevent the flow of negative halt waves of current from said source through said branch circuits, said controlled windings being so arranged that the fluxes they produce in said core are in opposite directions relative to said control winding, separate circuit elements connected in each of said branch circuits, and means responsive to the sum of the voltage drops across said elements.

5. In combination, a core of magnetic material having a definite saturation characteristic, a control winding thereon, a pair of controlled windings thereon, a circuit for energizing said control winding? with continuous current the direction of which is selectively reversible, a source of alternating current, said controlled winding being connected to said source of alternating current in parallel branch circuits, separate unidirectional conducting devices connected in each of said branch circuits, said controlled windings being so arranged that the fluxes they produce in said core are in opposite directions relative to said control winding, and separate electroresponsive devices connected in each of said branch circuits, said devices having their energlzation selectively oppositely varied in accordance with the direction of current in said control winding.

6. In combination, a core of magnetic material having a definite saturation characteristic, a control winding thereon, a pair of controlled windings thereon, a circuit for energizing said control winding with a selectively variable magnitude continuous current, a source of alternating current, said controlled windings being connected to said source of alternating current in parallel branch circuits, separate unidirectional conducting devices connected in each of said branch circuits, separate circuit elements serially connected in each of said branch circuits, the controlled winding in each of said branch circuits being disposed between its unidirectional conducting deviceand its circuit element, and electroresponslve means connected to be energized by the sum of the voltage drops across said elements.

AUS'I'YN L. WIHTELEY. LESLIE C. LUDBROOK.

US235862A 1937-01-02 1938-10-19 Magnetic amplifier Expired - Lifetime US2229952A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US118914A US2169093A (en) 1937-01-02 1937-01-02 Electrical control system
GB17191/38A GB514865A (en) 1937-01-02 1938-06-09 Improvements in and relating to directional saturable reactors

Publications (1)

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US2229952A true US2229952A (en) 1941-01-28

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Application Number Title Priority Date Filing Date
US118914A Expired - Lifetime US2169093A (en) 1937-01-02 1937-01-02 Electrical control system
US235862A Expired - Lifetime US2229952A (en) 1937-01-02 1938-10-19 Magnetic amplifier

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Application Number Title Priority Date Filing Date
US118914A Expired - Lifetime US2169093A (en) 1937-01-02 1937-01-02 Electrical control system

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US (2) US2169093A (en)
BE (1) BE425532A (en)
DE (1) DE709546C (en)
FR (2) FR831459A (en)
GB (2) GB508847A (en)

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2509738A (en) * 1948-05-29 1950-05-30 Gen Electric Balanced magnetic amplifier
US2567383A (en) * 1946-03-28 1951-09-11 Asea Ab Means for generating low-frequency electrical oscillations
US2585332A (en) * 1948-02-10 1952-02-12 Vickers Inc Electric controlling apparatus
US2613248A (en) * 1948-03-22 1952-10-07 Mccolpin Christie Corp Battery testing apparatus and method
US2615977A (en) * 1948-05-28 1952-10-28 Rca Corp Gain control circuit utilizing keyed magnetic amplifier
DE756138C (en) * 1941-04-08 1953-05-04 Siemens Ag Arrangement for setting the in uncontrolled state, the restrictors by flowing working stream of magnetic amplifiers
US2658132A (en) * 1950-01-06 1953-11-03 Welch Electric Company Inc Remote-control system for direct current welding
US2678419A (en) * 1946-09-30 1954-05-11 Bendix Aviat Corp Saturable transformer device
US2703388A (en) * 1950-05-16 1955-03-01 Automatic Elect Lab Magnetic cross valve circuits
US2715203A (en) * 1950-06-17 1955-08-09 Gen Electric Electric motor control circuit using saturable reactors
US2725519A (en) * 1952-03-31 1955-11-29 Westinghouse Electric Corp Magnetic amplifier electrical position control system
US2733306A (en) * 1952-07-29 1956-01-31 bedford
US2752545A (en) * 1953-11-18 1956-06-26 Allis Chalmers Mfg Co Control system utilizing magnetic amplifier for reference voltage
US2773131A (en) * 1953-04-06 1956-12-04 Honeywell Regulator Co Magnetic amplifier
US2778987A (en) * 1954-04-19 1957-01-22 Vickers Inc Multibranch magnetic amplifier with beneficially interrelated magnetic path
US2779910A (en) * 1952-09-18 1957-01-29 Sperry Rand Corp Three-phase magnetic amplifier
US2846524A (en) * 1955-02-07 1958-08-05 Sperry Rand Corp Magnetic amplifier circuit with outputs of opposite phase
US2879463A (en) * 1954-04-20 1959-03-24 Franklin S Malick Computer impedance changing with magnetic amplifier
US2902634A (en) * 1955-11-09 1959-09-01 Square D Co Motor control circuits
US2908857A (en) * 1955-06-20 1959-10-13 Westinghouse Brake & Signal Trigger circuit with memory action
US2910642A (en) * 1953-09-18 1959-10-27 Bendix Aviat Corp Magnetic amplifier system
US2997700A (en) * 1956-09-10 1961-08-22 Ibm Visual indicators for low voltage apparatus
WO1999060585A1 (en) * 1998-05-18 1999-11-25 Nmb (Usa), Inc. Variable inductor
US20040119577A1 (en) * 2002-12-20 2004-06-24 Robert Weger Coil arrangement with variable inductance

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DE975928C (en) * 1939-01-24 1962-12-13 Siemens Ag Means for controlling the current passage through dry rectifier
DE975610C (en) * 1939-02-14 1962-02-22 Siemens Ag Means for voltage control of AC circuits with chokes gleichstromvormagnetisierten
DE975927C (en) * 1939-03-28 1962-12-13 Siemens Ag Circuit for controlling the output by dry rectifiers DC
DE946371C (en) * 1939-10-14 1956-08-02 Siemens Ag Means for selbsttaetigen control of rectifiers means vormagnetisierter chokes
DE914864C (en) * 1940-08-21 1954-07-12 Siemens Ag controlled by bias throttle arrangement
DE755414C (en) * 1941-01-10 1953-01-05 Siemens Ag Regulating device controlled with over a magnetic Amplifier, gleichstromvormagnetisierten chokes
DE970823C (en) * 1941-03-29 1958-10-30 Siemens Ag Magnetverstaerker
DE899370C (en) * 1941-07-05 1953-12-10 Siemens Ag As Magnetverstaerker usable choke assembly
DE902633C (en) * 1941-07-25 1954-01-25 Siemens Ag magnetic Amplifier
DE966572C (en) * 1941-10-31 1957-08-22 Siemens Ag magnetic Amplifier
DE969296C (en) * 1942-08-20 1958-05-22 Siemens Ag An arrangement for maintaining the control effect of magnetic amplifiers for small Verbraucherstroemen
DE966234C (en) * 1943-05-25 1957-07-18 Siemens Ag magnetic Amplifier
DE976011C (en) * 1943-09-28 1963-01-10 Siemens Ag Control device with gleichstromvormagnetisierten chokes
DE975369C (en) * 1944-06-30 1961-11-16 Siemens Ag Magnetic regulator having a magnetic Brueckenanordnung
DE972995C (en) * 1944-09-22 1959-11-12 Siemens Ag magnetic Amplifier
BE475022A (en) * 1945-06-25
BE475361A (en) * 1946-08-27
US2596685A (en) * 1946-09-21 1952-05-13 Asea Ab Regulator with saturable core
DE975223C (en) * 1946-09-21 1961-10-05 Asea Ab An electrical regulator having a transductor
US2731593A (en) * 1949-05-14 1956-01-17 Hauptman Robert Electrical system
BE495835A (en) * 1949-05-20 1900-01-01
US2554203A (en) * 1949-11-10 1951-05-22 Gen Electric Magnetic amplifier control system
NL84459C (en) * 1950-06-26
DE976370C (en) * 1950-12-05 1963-07-25 Siemens Ag Control circuit with pre-magnetized chokes
DE945337C (en) * 1951-04-03 1956-07-05 Fritz Kuemmel Dr Ing Arrangement for enhancing the Brueckenspannung at Wechselstrombruecken with the aid of pre-magnetized chokes
DE975300C (en) * 1951-06-02 1961-11-02 Licentia Gmbh Arrangement for supplying consumers with veraenderlicher counter voltage using magnetic amplifiers
DE976237C (en) * 1951-10-27 1963-05-16 Siemens Ag Magnetverstaerker
DE963359C (en) * 1952-01-17 1957-05-09 Licentia Gmbh Amplifier section for photoelectric switch and control equipment
NL180325B (en) * 1952-08-06 Goodyear Tire & Rubber
DE1143583B (en) * 1952-12-03 1963-02-14 Bbc Brown Boveri & Cie Circuitry for generating approximated rectangle-shaped electrical pulses, in particular for controlling power converters
DE1045463B (en) * 1953-05-18 1958-12-04 Siemens Ag Arrangement for reducing or repressing of interfering Kreisstroemen in Magnetverstaerkern
DE972790C (en) * 1953-09-22 1959-09-24 Siemens Ag Contactless relay based vormagnetisierter Reactors
DE1061889B (en) * 1954-08-23 1959-07-23 Siemens Ag Phasenregelbruecke for connection to a three-phase network
US2754474A (en) * 1955-04-13 1956-07-10 Philip W Barnhart Arrangement for producing full-wave output from half-wave magnetic amplifiers
US2892092A (en) * 1955-12-08 1959-06-23 Vickers Inc Power transmission
US2922946A (en) * 1955-12-19 1960-01-26 Sperry Rand Corp Saturable reactor devices
US2933617A (en) * 1956-05-25 1960-04-19 Hughes Aircraft Co Magnetic amplifier circuit
DE1227673B (en) * 1956-06-27 1966-10-27 Licentia Gmbh Nonlinear electrical transducer
US2854587A (en) * 1956-08-15 1958-09-30 Westinghouse Electric Corp Switching systems
US2980847A (en) * 1957-08-12 1961-04-18 Westinghouse Electric Corp Switching apparatus for magnetic amplifiers
DE1140715B (en) * 1957-12-11 1962-12-06 Licentia Gmbh An arrangement for contactless switching on and off the current flow through a direct current consumer
US3274580A (en) * 1962-08-10 1966-09-20 Electronics Corp America Radiation detection device circuits for use in flame sensing
DE1296256B (en) * 1967-01-31 1969-05-29 Wuetherich Richtungsabhaengig imaging DC transducer
WO2013082668A1 (en) * 2011-12-09 2013-06-13 Applied Superconductor Pty Ltd Fault current limiter

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE756138C (en) * 1941-04-08 1953-05-04 Siemens Ag Arrangement for setting the in uncontrolled state, the restrictors by flowing working stream of magnetic amplifiers
US2567383A (en) * 1946-03-28 1951-09-11 Asea Ab Means for generating low-frequency electrical oscillations
US2678419A (en) * 1946-09-30 1954-05-11 Bendix Aviat Corp Saturable transformer device
US2585332A (en) * 1948-02-10 1952-02-12 Vickers Inc Electric controlling apparatus
US2613248A (en) * 1948-03-22 1952-10-07 Mccolpin Christie Corp Battery testing apparatus and method
US2615977A (en) * 1948-05-28 1952-10-28 Rca Corp Gain control circuit utilizing keyed magnetic amplifier
US2509738A (en) * 1948-05-29 1950-05-30 Gen Electric Balanced magnetic amplifier
US2658132A (en) * 1950-01-06 1953-11-03 Welch Electric Company Inc Remote-control system for direct current welding
US2703388A (en) * 1950-05-16 1955-03-01 Automatic Elect Lab Magnetic cross valve circuits
US2715203A (en) * 1950-06-17 1955-08-09 Gen Electric Electric motor control circuit using saturable reactors
US2725519A (en) * 1952-03-31 1955-11-29 Westinghouse Electric Corp Magnetic amplifier electrical position control system
US2733306A (en) * 1952-07-29 1956-01-31 bedford
US2779910A (en) * 1952-09-18 1957-01-29 Sperry Rand Corp Three-phase magnetic amplifier
US2773131A (en) * 1953-04-06 1956-12-04 Honeywell Regulator Co Magnetic amplifier
US2910642A (en) * 1953-09-18 1959-10-27 Bendix Aviat Corp Magnetic amplifier system
US2752545A (en) * 1953-11-18 1956-06-26 Allis Chalmers Mfg Co Control system utilizing magnetic amplifier for reference voltage
US2778987A (en) * 1954-04-19 1957-01-22 Vickers Inc Multibranch magnetic amplifier with beneficially interrelated magnetic path
US2879463A (en) * 1954-04-20 1959-03-24 Franklin S Malick Computer impedance changing with magnetic amplifier
US2846524A (en) * 1955-02-07 1958-08-05 Sperry Rand Corp Magnetic amplifier circuit with outputs of opposite phase
US2908857A (en) * 1955-06-20 1959-10-13 Westinghouse Brake & Signal Trigger circuit with memory action
US2902634A (en) * 1955-11-09 1959-09-01 Square D Co Motor control circuits
US2997700A (en) * 1956-09-10 1961-08-22 Ibm Visual indicators for low voltage apparatus
WO1999060585A1 (en) * 1998-05-18 1999-11-25 Nmb (Usa), Inc. Variable inductor
US6317021B1 (en) 1998-05-18 2001-11-13 Nmb (Usa) Inc. Variable inductor
US20040119577A1 (en) * 2002-12-20 2004-06-24 Robert Weger Coil arrangement with variable inductance
DE10260246B4 (en) * 2002-12-20 2006-06-14 Minebea Co., Ltd. Coil arrangement with variable inductance

Also Published As

Publication number Publication date
US2169093A (en) 1939-08-08
GB514865A (en) 1939-11-20
GB508847A (en) 1939-07-03
FR50939E (en) 1941-05-10
DE709546C (en) 1941-08-20
FR831459A (en) 1938-09-05
BE425532A (en) 1938-02-28

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