US862361A - Electrical apparatus. - Google Patents

Electrical apparatus. Download PDF

Info

Publication number
US862361A
US862361A US27016305A US1905270163A US862361A US 862361 A US862361 A US 862361A US 27016305 A US27016305 A US 27016305A US 1905270163 A US1905270163 A US 1905270163A US 862361 A US862361 A US 862361A
Authority
US
United States
Prior art keywords
core
portions
winding
flexible
rotatable
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
US27016305A
Inventor
Wilbur H Thompson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CBS Corp
Original Assignee
Westinghouse Electric and Manufacturing Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Westinghouse Electric and Manufacturing Co filed Critical Westinghouse Electric and Manufacturing Co
Priority to US27016305A priority Critical patent/US862361A/en
Application granted granted Critical
Publication of US862361A publication Critical patent/US862361A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F29/00Variable transformers or inductances not covered by group H01F21/00
    • H01F29/02Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings
    • H01F29/04Variable transformers or inductances not covered by group H01F21/00 with tappings on coil or winding; with provision for rearrangement or interconnection of windings having provision for tap-changing without interrupting the load current

Definitions

  • v v V My invention relates to electrical apparatus and it has special reference to apparatus having means for varying the magnetizing effect of its winding or windings.
  • the object of my invention is to provide an apparatus of the general character above indicated that shall have a flexible winding which may be either disposed upon its core in two or more equal and opposing coils or be adjusted to provide either opposing or assisting turns of any number .within the limits imposed by the length of the winding.
  • My invention is primarily intended for alternating current voltage regulation, and I will therefore describe it as applied to such use. I believe the invention to be of broader scope and suitable for other uses, however, and I therefore desire it to be understood that no specific application which may be hereinafter described shall be held to exclude any alternating current or direct current apparatus the structural and operative characteristics of which are the equivalents of those here set forth, even though such apparatus may be utilizedin different relations to effect a specifically different result.
  • Potential regulators may be divided into two general classes, one of which embodies transformers having spaced leads to which one side of a circuit is successively connected to vary the voltage applied thereto and which therefore involves numerous circuit interruptions.
  • other class of regulators depends for its operation upon the position of a winding on a rotatable core with respect to a stationary winding which is in inductive relation thereto. This construction involves a considerable airgap in the magnetic circuit and necessitates a careful alinement of the rotating member, which makes the construction relatively expensive.
  • the regulator of my invention may be constructed with a comparatively inexpensive core and may effect a wide regulation without circuit interruptions.- In general, it comprises one or more flexible windings of cable, wire-braid or chain formation that may be readily wound, unwound and removed without injury to the conductor itself or to its insulation. In case the flexible winding is in two portions, they may be wound upon parallel portions of a magnetizable core, which are-either rotatable with respect to the remainder of the core or are provided with rotatably mounted spools or bobbins, though the use of spools or bobbins was not originally proposed by me. One end of each flexible.
  • winding may be connected to a slip-ring which is mounted upon one of the rotatable core members or spools and the opposite end of the same winding may be connected to a slip-ring on the other rotatable core member or spool, so that the two windings may be continuously connected in series with each other and-in series with a supply line.
  • the flexible construction of the winding itself and the rotatable mounting provide means for transferring all or a portion of the turns of each winding from one of the core portions to the other, so that each core portion shall always have an invariable number of turns thereon.
  • collector rings When collector rings are mounted-in such a position that the magnetic flux in the core passes through them, it is advisable to provide an opening in the ring in which insulation may be inserted to prevent the induction of a short-circuited current in the ring and, in regulation, where such short-circuited currents would be excessive, a pair of narrow brushes, which are connected sby an inductive or other suitable resistance, may be advantageously employed to engage the ring at differentpoints, the circuit connection being made to themiddle-point of the interposed resistance instead of to a single brush, which would in some instances shortcircuit the ring or break the circuit.
  • the turns of both portions of the flexible winding are so arranged that the electromotive forces induced in all the turns of both portions may be added together and act in one direction or by simultaneously rotating the movable members of the core, the turns of one portion of the flexible winding may partially or whollyneutralize the turns of the other portion, or' the electromotive forces generated may be added together in the opposite direction.
  • the voltage delivered from the line may be varied from a maximum value obtained when all the turns are acting in the same direction, corresponding to that of the line voltage, to a minimum value obtained when all the turns act in opposition to the line voltage.
  • the principal advantage in providing two flexible portions, the turns ofwhich may be interchanged in position, lies in the fact that the available space on the core is completely occupied at all times.
  • Figure 1 is' a diagrammatic .view of a regulator constructed in accordance therewith, in which two portions'of the core are rotatably mounted.
  • Fig. 2 is a .32 that are connected to the terminals of a'preventive similar view, in which spools or bobbins are rotatably mounted upon two parallel portions oi a continuous core, and
  • Fig. '3 is adiagrammatic view ofa modified arrangement in which a single portion of a magnetiza ble core is rotatable. 5
  • a magnetizable core 1 comprises two fixed body. portions 2 and 3 and two parallel, rotatably-moirnted portions 4 and 5.
  • the rotatable portions 4' and .5 are provided with shaft extensions 6 and 7 upon which are mounted slip-rings 8, 8, 9 and 9 and a pair of similar pinions 10 and 11.
  • the rotatable por tions may be simultaneously driven by the gear wheel 12 which engages the pinions l0 and .11 and may be actuated by any convenient means, such as a handwheel 13.
  • a magnetizing winding 16 may be mounted upon the fixed core portion 3 and be connected across an electric supply line 17-18.
  • a flexible winding 19 is connected to the slip-ring 8 and is partially coiled'about the rotatable poption 4, the remaining turns being wound upon the rotatable portion 5 and the other end being connected through the slip-rings 9 and 9, which are connected by a conductor 19, to a similar winding 20, the remaining terminal oi which r is connected to the slip-ring 8
  • the turns of bothfiexible windings are transferred from one portion to the other until they mean interchanged.
  • the available space of the two core portions may be entirely occupied at all times by the proper'rotation of the core portions, and the turns of the flexible windings may all actin the one direction or the other, or may entirely oppose each other when the; slip-rings 8 and 8 are connected in series with the interrupted line conductor 18, which causes the entire current supplied from the line 17 and 18 to pass through the two flexible windings.
  • portions of the magnetizable core 21 that correspond in position to the portions 4 and 5 of'Fig. 1 are respectively provided with spools or bobbins 22 and'23 upon which are coiled fiexihle'wlridings 24 and 25.
  • the ends of wind-- ing.24 are connected to s'li'p-rings26 and and the ends of the winding 25 are connected to slip-rings 28 and 29,
  • Each; of the rings is pr'ovided with two bru'shes 31 and resistance 33,- the middle points of the resistances that are attached to the brushes making contact with the rings 26 and 28 being connected to the terminals of the interrupted line conductor .18 in order to connectthe flexible winding series in the circuit 17" 18 and at the same time'to avoid harmful short ci'r'cirits, and the middle points oi the resistances 35 that are connected to-the briishes that make Contact with the rings 2. 7 and 29 being connected together. )1
  • the rotatable members 37 and 40 are provided with pinions' 41 and 42 which are engaged by a driving gear wheel 43. v
  • the driving gear wheel 43 may be operated By this arrangement, the simultaneous rotation of the members 37 and 40 transfers one or more of the turns from the magnetizing core portion 37 to the drum 10, thus providing a'regulatio'n from a normal voltage of a supply line 4546 when all the turns are on the drum 40' to a maximum variation therefrom when all the turns are upon the magnetizable portion 37.
  • the comblnatlon with amagnetlzable member comprising two opposite fixed portions, a primary wlnding located thereon, and ltwo opposite rotatable portions adjacent to 'the fixed portlons, of a flexible secondary winding rotatable portions to the other,
  • the combination with a magnetlzable core comprising tlons, of a flexible winding the turns of. wlilch may be concentrated on either one of the rotatable portions or be dis ..tribu'ted between them.

Description

No. 862,361. PATENTED AUG. 6, 1907.
, w. H. THOMPSON.
ELECTRICAL APPARATUS.
APPLICATION FILED JULY17. 1905.
2 SHEETS-SHEET 1.
10 a .3 1/ 5 H0 1| 1 M M Z8 25 I 34 31 Z5 f 33 E 33 Z5 Z4 32 3/ 31 m: w h WITNESSES: 39 50 50 INVENTOR No. 862,361. PATENTED AUG. '6, 1907. w. H. THOMPSON.
ELECTRICAL APPARATUS. APPLIOATION FILED JULY 17, 1905.
zsnnms-snnm 2.
n 0 n magnezflc WITNESSES: INVENTOR zfiw 4 MJKM,
I ATSORNEY UNITED STATES" PATENT OFFICE. f
WILBUR H. THOMPSON, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA,
ELECTRICAL APPARATUS.
Specification of Letters Patent.
' Patented Aug. 6, 1907.
Application filed July 17, 1905. 7 Serial No. 27 ,1
have invented a new and useful Improvement in Electrical Apparatus, of which the following is a specification. v v V My invention relates to electrical apparatus and it has special reference to apparatus having means for varying the magnetizing effect of its winding or windings.
The object of my invention is to provide an apparatus of the general character above indicated that shall have a flexible winding which may be either disposed upon its core in two or more equal and opposing coils or be adjusted to provide either opposing or assisting turns of any number .within the limits imposed by the length of the winding.
My invention is primarily intended for alternating current voltage regulation, and I will therefore describe it as applied to such use. I believe the invention to be of broader scope and suitable for other uses, however, and I therefore desire it to be understood that no specific application which may be hereinafter described shall be held to exclude any alternating current or direct current apparatus the structural and operative characteristics of which are the equivalents of those here set forth, even though such apparatus may be utilizedin different relations to effect a specifically different result.
Potential regulators, as heretofore generally constructed, may be divided into two general classes, one of which embodies transformers having spaced leads to which one side of a circuit is successively connected to vary the voltage applied thereto and which therefore involves numerous circuit interruptions. ilhe other class of regulators depends for its operation upon the position of a winding on a rotatable core with respect to a stationary winding which is in inductive relation thereto. This construction involves a considerable airgap in the magnetic circuit and necessitates a careful alinement of the rotating member, which makes the construction relatively expensive. I
The regulator of my invention may be constructed with a comparatively inexpensive core and may effect a wide regulation without circuit interruptions.- In general, it comprises one or more flexible windings of cable, wire-braid or chain formation that may be readily wound, unwound and removed without injury to the conductor itself or to its insulation. In case the flexible winding is in two portions, they may be wound upon parallel portions of a magnetizable core, which are-either rotatable with respect to the remainder of the core or are provided with rotatably mounted spools or bobbins, though the use of spools or bobbins was not originally proposed by me. One end of each flexible.
winding may be connected to a slip-ring which is mounted upon one of the rotatable core members or spools and the opposite end of the same winding may be connected to a slip-ring on the other rotatable core member or spool, so that the two windings may be continuously connected in series with each other and-in series with a supply line. The flexible construction of the winding itself and the rotatable mounting provide means for transferring all or a portion of the turns of each winding from one of the core portions to the other, so that each core portion shall always have an invariable number of turns thereon.
When collector rings are mounted-in such a position that the magnetic flux in the core passes through them, it is advisable to provide an opening in the ring in which insulation may be inserted to prevent the induction of a short-circuited current in the ring and, in regulation, where such short-circuited currents would be excessive, a pair of narrow brushes, which are connected sby an inductive or other suitable resistance, may be advantageously employed to engage the ring at differentpoints, the circuit connection being made to themiddle-point of the interposed resistance instead of to a single brush, which would in some instances shortcircuit the ring or break the circuit.
The turns of both portions of the flexible winding are so arranged that the electromotive forces induced in all the turns of both portions may be added together and act in one direction or by simultaneously rotating the movable members of the core, the turns of one portion of the flexible winding may partially or whollyneutralize the turns of the other portion, or' the electromotive forces generated may be added together in the opposite direction. In this way, if the magnetizable core is energized by a stationary winding connected across a constant potential supply circuit and if the flexible windings are connected in series with the same line by a simultaneous actuation of the two rotatable members of the core, the voltage delivered from the line may be varied from a maximum value obtained when all the turns are acting in the same direction, corresponding to that of the line voltage, to a minimum value obtained when all the turns act in opposition to the line voltage.
The principal advantage in providing two flexible portions, the turns ofwhich may be interchanged in position, lies in the fact that the available space on the core is completely occupied at all times.
' My invention'is illustrated in the accompanying drawings, in which Figure 1 is' a diagrammatic .view of a regulator constructed in accordance therewith, in which two portions'of the core are rotatably mounted. Fig. 2 is a .32 that are connected to the terminals of a'preventive similar view, in which spools or bobbins are rotatably mounted upon two parallel portions oi a continuous core, and Fig. '3 is adiagrammatic view ofa modified arrangement in which a single portion of a magnetiza ble core is rotatable. 5
Referring to Fig. 1, a magnetizable core 1 comprises two fixed body. portions 2 and 3 and two parallel, rotatably-moirnted portions 4 and 5. -The rotatable portions 4' and .5 are provided with shaft extensions 6 and 7 upon which are mounted slip- rings 8, 8, 9 and 9 and a pair of similar pinions 10 and 11. The rotatable por tions may be simultaneously driven by the gear wheel 12 which engages the pinions l0 and .11 and may be actuated by any convenient means, such as a handwheel 13. A magnetizing winding 16 may be mounted upon the fixed core portion 3 and be connected across an electric supply line 17-18. Onei end of a flexible winding 19 is connected to the slip-ring 8 and is partially coiled'about the rotatable poption 4, the remaining turns being wound upon the rotatable portion 5 and the other end being connected through the slip-rings 9 and 9, which are connected by a conductor 19, to a similar winding 20, the remaining terminal oi which r is connected to the slip-ring 8 When the two portions 4 and 5 are simultaneously rotated in the same direction, the turns of bothfiexible windings are transferred from one portion to the other until they mean interchanged. In' this way, the available space of the two core portions may be entirely occupied at all times by the proper'rotation of the core portions, and the turns of the flexible windings may all actin the one direction or the other, or may entirely oppose each other when the; slip- rings 8 and 8 are connected in series with the interrupted line conductor 18, which causes the entire current supplied from the line 17 and 18 to pass through the two flexible windings.
Referring now to Fig. 2 of the drawings, portions of the magnetizable core 21 that correspond in position to the portions 4 and 5 of'Fig. 1 are respectively provided with spools or bobbins 22 and'23 upon which are coiled fiexihle'wlridings 24 and 25. The ends of wind-- ing.24 are connected to s'li'p-rings26 and and the ends of the winding 25 are connected to slip- rings 28 and 29,
rings 26 and 29 being mounted upon the respective. ends of thespool 22 and rings 28 and 27 being mount= ed upon the respective ends of spool 23. A small segment of each ring is removed and is replaced bya segmentiii) of insulating material in order to avoid the generationof currents in the rings.
Each; of the rings is pr'ovided with two bru'shes 31 and resistance 33,- the middle points of the resistances that are attached to the brushes making contact with the rings 26 and 28 being connected to the terminals of the interrupted line conductor .18 in order to connectthe flexible winding series in the circuit 17" 18 and at the same time'to avoid harmful short ci'r'cirits, and the middle points oi the resistances 35 that are connected to-the briishes that make Contact with the rings 2. 7 and 29 being connected together. )1
In case a wide variation in voltage isnot necessary, the construction of the we may be simplified and present s aller dimensions, by nieans of a modifies ti'on' which i disclosed in Fig. s, in which a flexible winding se'is'wound upon a'rotatsble' core portion 3?,
seasm the portion 37 and the other end being connected to a slip-ring 39 which is mounted on the shaft of a rotatable drum 40 of non-magnetizable material.
The rotatable members 37 and 40 are provided with pinions' 41 and 42 which are engaged by a driving gear wheel 43. v The driving gear wheel 43 may be operated By this arrangement, the simultaneous rotation of the members 37 and 40 transfers one or more of the turns from the magnetizing core portion 37 to the drum 10, thus providing a'regulatio'n from a normal voltage of a supply line 4546 when all the turns are on the drum 40' to a maximum variation therefrom when all the turns are upon the magnetizable portion 37. The
454 6 and thecore may be magnetized in the usual manner bya winding 47, which may be connecte across the line 45'46. I claim as my invention: I
. 1. The comblnatlon with amagnetlzable member comprising two opposite fixed portions, a primary wlnding located thereon, and ltwo opposite rotatable portions adjacent to 'the fixed portlons, of a flexible secondary winding rotatable portions to the other,
2. The combination with a magnetlznble core comprlslng two rotatable portlons, of a flexible winding the turns of which may be transferred to either core portion or be distributed between the two;
3. The combination with a magnetlzable core comprising tlons, of a flexible winding the turns of. wlilch may be concentrated on either one of the rotatable portions or be dis ..tribu'ted between them.
4. The combination with a magnetlz'able core comprising and a magnetizing winding located thereon, of a flexible winding the turns or which may be transferred from one rotatable core portion to the other so that they will either did the fixed winding or act in opposition thereto.
5. The combination .wlth a magnetlzable core and a magnetizing tvlndlng therefor, o! a flexible secondary winding that is mounted upon parallel core portions, and means foitransferrln'g the turns of said flexible winding to provldeclther two coils or four coils.
6; The comblnatl'on with a ma'gnetlznble core and a magnetizing .wlndlng therefor, of a flexible regulating winding that is mounted np'on parallel core 'portlons, and means for transferring the-turns of sald wlndlng to provide tour coils of equal length, tour coils-of unequal length or two cells or equal length.
7. The combination with n fixed magnetizing wlndlng and a magnetlzjable core two portions of which are re tatable, or a pair of slnallar flexible wlndlngs connected in series and wound on sold rotatable portions, and means for lnterchanglng' a part or all of the turns or said flexible windings.
8 The combination with a mngn'etlzable core, two pnrnl lel portions of whlch are rotatable, a fixed magnetizing wlndlng mounted on sold core and two similar flexible and lire connected in series, of means for rotating said core portions to'eifect transference or the turns of the two flexible windings.
9. 'A voltage regulator-that cornprlses a magnetlznble core, two portions of which are rotatable, a fixed inagnetl'zmy; wlndlng mounted on said core and two similar flexible and are connected in series. 7
n. The combination with a inagnetlzhble core. a mag harming winding therefor and two similar ll'exlble'wlndlugs which are mounted on two rotatable portlon's of .s'ald bdrm-and are so connected that the electromotlve forces indiiced therein are added together, or means for interone'end being connected to a slip-ring 38 attached to.
flexible winding is connected in series with the line that is transferable, ln'whole or in part, from one or said;
two opposite rotatable portions and adjacent fixed porwindings that are mounted on said rotatable core portions by any" convenient-means, such asa hand-wheel 44.
two opposite rotatable portlonmadjacent fixed portions winnings that are mounted on said rotatable core portions I changing a part or all of the turns of the flexible windings so that the electromotive forces induced therein partially or wholly neutralize each other. 7
11. The combination with a magnetizable core, a mag netizing winding therefor, and two similar flexible windings that are mounted upon rotatable portions of said core, said flexible windings being so connected that the electromotive forces induced therein are added together, of means for interchanging a part or all of the turns of the windings so that the electromotive forces induced therein are partially or wholly opposite in direction.
12. The combination with a magnetic circuit that comprises a continuous magnetizahle core on two rotatable portions of which are mounted flexible windings, of means for interchanging a part or all of the turns of the windings so that the electromotive forces induced therein are partially or wholly opposite in direction.
13. The combination with a magneti'zable core two p0r tions of which are rotatably mounted, and a magnetizing winding therefor, of a flexible winding which is mounted on said rotatable portions and means for simultaneously rotating said portions comprising a driving gear wheel and a'palr of pinions which are fixed to shaft extensions ofthe rotatable portionsp v 14. The combination with a magnetizable core, a pair of similar, rotatably mounted portions thereof being pro vided with shaft, extensions,- pinions attached thereto, a magnetizing winding for said core, and means for simultaneously rotating said portions that comprises a driving wheel which engages said pinions, of a winding composed 'of flexible conductors and mounted on the rotatable core portions.
15. The combination with a magnetizable core, a pair of similar, rotatably mounted portions thereof being provided with shaft extensions, pinions attached thereto, a magnetizing winding for said core, and means for simultaue ously rotating said portions that comprises a driving wheel which engages said pinions, of a winding that is composed of flexible conductors and is mounted on the rotatable core portions, and means for varying the electro motive force induced in the fiexiblewinding without interrupting the circuit connections.
16. The combination with an alternating current 'supply circuit, a magnetizing winding that is connected across the circuit and is mounted on a. magnetizable core, two similar portions of which are rotatably mounted, of a pair of flexible secondary windings that are disposed upon the rotatable core portions and are connected in series with the supply circuit, the positions of a part or all of the turns of the flexible winding being interchanged as the said core portions are simultaneously rotated, without interrupting the circuit connections.
In testimony whereof, I have hereunto subscribed my name this 12th day of July, 1905.
- WILBUR H. THOMPSON. Witnesses:
ALBERT C. LASHER, BIRNEY Hmns
US27016305A 1905-07-17 1905-07-17 Electrical apparatus. Expired - Lifetime US862361A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US27016305A US862361A (en) 1905-07-17 1905-07-17 Electrical apparatus.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US27016305A US862361A (en) 1905-07-17 1905-07-17 Electrical apparatus.

Publications (1)

Publication Number Publication Date
US862361A true US862361A (en) 1907-08-06

Family

ID=2930813

Family Applications (1)

Application Number Title Priority Date Filing Date
US27016305A Expired - Lifetime US862361A (en) 1905-07-17 1905-07-17 Electrical apparatus.

Country Status (1)

Country Link
US (1) US862361A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2598321A (en) * 1948-05-21 1952-05-27 Rca Corp Filament heating transformer having a variable output voltage
US2982929A (en) * 1958-10-29 1961-05-02 Collins Radio Co Variable inductor
US2993182A (en) * 1955-10-10 1961-07-18 Ellis Charles Richard Variable inductance
US3030563A (en) * 1959-08-24 1962-04-17 Pacific Scientific Co Servomotor control circuit
US4325045A (en) * 1979-08-02 1982-04-13 U.S. Philips Corporation Device for providing windings on closed ring cores

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2598321A (en) * 1948-05-21 1952-05-27 Rca Corp Filament heating transformer having a variable output voltage
US2993182A (en) * 1955-10-10 1961-07-18 Ellis Charles Richard Variable inductance
US2982929A (en) * 1958-10-29 1961-05-02 Collins Radio Co Variable inductor
US3030563A (en) * 1959-08-24 1962-04-17 Pacific Scientific Co Servomotor control circuit
US4325045A (en) * 1979-08-02 1982-04-13 U.S. Philips Corporation Device for providing windings on closed ring cores

Similar Documents

Publication Publication Date Title
US3544868A (en) Dynamo electric machines
US3614692A (en) Variable induction device
US862361A (en) Electrical apparatus.
US2174652A (en) Dual voltage magnetic motor
US3328735A (en) Electrical transformer
US1234914A (en) Dynamo-electric machine.
US1702454A (en) Protective relay
US2348055A (en) Electric translating apparatus
US2356166A (en) Protective means for electrical contacts
US1951733A (en) System and apparatus for power factor correction
US1646028A (en) Electric safety apparatus
US2205476A (en) Transforming apparatus
US2295303A (en) Tap changer
US1013108A (en) Electrical apparatus.
US2780741A (en) Direct current dynamoelectric machine
US2112046A (en) Control system for electric locomotives
US1939433A (en) Electric valve converting system and excitation apparatus therefor
US1140920A (en) Transformer.
US1835550A (en) System of motor control
US2366679A (en) Electric circuit
US803253A (en) Electric regulator or controller.
US992300A (en) Electromagnetic apparatus.
US1364944A (en) Electromagnetic switch
US960383A (en) Dynamo-electric machine.
US1030617A (en) Electric controller.