US891721A - Starter for electric motors. - Google Patents

Description

vPA'I'ENIED JUNE 23, 1908.

' W.A C. O'BRIEN. STARTER FOR ELECTR MOTGRS. APPLIOATION FILED APB. 9, 1907. RENEW!) nomas, 19M.

2 SHEETS-BHEBT 1 Wi im emes PATENTED JUNE 23, 1908.

W. C.'0'BETEN.

STAETEE EUR ELECTRIC MOTORS.

APPLICATION FILED APRV 9, 1907. RENEWED NOV.2Z, 1907.

` 2 SHEETS-SHEET 2.

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attoznuj UNITED sTATEs PATENT oFFroE.

WILLIAM C. OBRIEN, OF BALTIMORE, MARYLAND, ASSIGNOR TO MONITOR MANUFACTURING `COMPANY OF BALTIMORE CITY, OF BALTIMORE, MARYLAND, A CORPORATION OF MARY- LAND.

Specification of Letters Patenti Patented June 23, 190s",

Application filed April 9, 1967, Serial No. 367,192. Renewed November `22, 1907. Serial No. 403,342.

To all whom 'it may concern:

Be it known that I, WILLIAM C. OBRIEN, a citizen of the United States, residing at Baltimore, in the State of Maryland, have invented certain new and'useful Improvements in Starters for Electric Motors, vof which the following is a specication.

This invention relates to improvements in automatic starters for electric motors, of the kind shown in my copending application, Seriqal No. 333,987, iled September 10, 1906, in which the cutting out of the starting resistance is regulated by the quantity of current flowing in the armature circuit.

In the accompanying drawing, Figure 1 is a side elevation, partly in section of] a starter suitable for cutting out a single step or section of resistance from the armature circuit, the solenoids of the starter being connected in series, and the parts being shown in their normal 'positions Fig. 2 is a similar view, showing the positions of the parts at the time the line switch is `first closed and before the current in the arman ture circuit has fallen to a predetermined quantity; Fig. 3 is a view of a similar starter, with the arts in normal positions, the coils of the horlding solenoids being connected in shunt to the terminals-'of the line switch, and ,the coils of the regulating solenoid being connected in series with the starting resistance and armature, and Fig.I 4 is a similar view, of the starter shown in Fig. '3, with the line switch closed and the regulating solenoid and starting resistance cut out.

Referring to Figs. 1 and 2 of the drawing, L and L indicate the terminals of the line or Vsupply circuit and S indicates the line switch'for connecting the motor M to the line through the motor starter A. The ar'- mature circuit of the motor extends from the line switch. terminal 1 through conductor 2, solenoid coils 3, conductor 4, solenoid coils `5, conductor 6, starting resistance 7, conductor 8, stationary contact 9, thence by conductor-10 to the brush of the armature a and thence by conductor 11 to the line switch terminal 12. The motor shown in the drawing is a shunt wound motor and its field f is connected to the switch terminals 1 and 12 through conductors 2, 2 and 11. The coils 3 and 5 of solenoids B and C, respectively, are ol low resistance and adapted to carry the entire armature'current and the solenoids are vertically arcross bars 13 and 14 of a suitable supporting frameY D. An arm 15 depends from the lower cross bar of the frame, midway be-4 tween the solenoids,'and the lever 16 iscentrally supported on this arm by a pivot pin A switch arm 1,8, rigidly connected with the lever 16, is adapted to bemovedl into and out of engagement with the fixed contact piece 9, according to the direction in which the lever 16 is rocked.A The switch arm is' connected to the conductor 4, between the coils of the solenoids by'a branch conductor 19; When the switch s, formed by the switch arm 18 and the stationary contact piece 9 is closed, it will be noted that the conductor 19, switch arm and contact pieceform a shunt circuit around the solenoid O and the resistance 7.

The lever 16 supports at its ends the cores of the solenoids B and O and the switch s is held normally open Aby the core 20 of the solenoid B which is heavier than the core 21 of the solenoid C. The core 20, made of solid iron or steel, is not attached to the lever 16 but merely rests upon one end of it, so that the core can. move without moving the leve'r. The core 21 as shown in the draw ing, is -of the same external dimensions as the core 20, but it is made of tubular iron or steel so as to be lighter than the core 20, and at its lower end the 'core 21 is connected to the lever 16 by a pin 22 extending through the core and through a slot 23 in the lever, Vso that the core and the lever will necessarily move together.

, The operation of the starter shown in Fig. 1 is as follows: As long as the line switch S remains in the open position, as shown in said gure,'the in the positions s Town. As soon as the line switch is closed, current passes through both solenoids, the starting resistance and the motor. The solenoid core 20 is instantly drawn up, as shown in Fig. 2, against a magnet core 24, arranged in the upper end ofthe coil 3 and energized thereby.A When the core 20 is lifted from-the lever 16 the core 21 of the solenoid C is left without mechanical support, as s'hown in Fig. 2, and is free to move downward, but the windings of thel latarts of the starter remain ter solenoid are so proportioned that its core will be held up as ong as the current inthe armature circuit is above the normal iull 'load current of the armature, or any predetermined quantity. The switch s, will thus be held open, and the resistance 7 maintained in the armature circuit after thc line switch is closed, until the current flowing in the armature circuit is reduced to a predetermined safe quantity, by the rotation of thc armature, when the core 21 will drop and move the lever 16 and the switch arm 18 to close the switch s. The armature` current will then flow from the terminal 1, around the coils of solenoid B and thence through conductor 19 and switch s to the armature, thus short circuiting the coils `of solenoid C and the starting resistance 7. The core 20 will remain up and thelcorel 21 will remain down as long as the motor* runs under normal conditions; but when the line switch is opened, 0r the voltage on the line, is,abnor mally lowered, the solenoid Bfwillbe deenergize'd or weakened and the core 20 will drop'ontothe lever and thus force the lever, switch arm and core 21 back into their nor malpositions, so that the switch s will be in I 1open position and the resistance7 and coils of solenoid C will be in circuit with the armature.

.When the motor starts with a load the current in the armature circuit Will always be suiiicient to raise the core of the holding solenoid when the line switch is first closed, and after said core has moved into engagement with the magnet core 24, it will be supported by the core 24 if only a small quantity positions.

of current flows through the armature circuit thereafter. r

.When the motor starts without load, it`

may be desirable, in order to insure the upwardy movement of the core of the holding solenoid, to connect the coils of the latter in shuntto the line switch terminals, instead of in series with the motor armature. This is shown in Figs. 3 and 4. In these figures of the drawing, the wire 2, leading from the switch terminal 1 is grounded at 26 on the frame D. From the frame a wire 27 leads to one end ofthe coils 3 ofthe holding solenoid B and a conductor 28 extends from the `other end of the solenoid coils to the opposite switch terminal 12. The regulating so enoid coil is connected in series with the starting resistance and armature, the coil being connected at one endto the conductor 6, and'at the other end, by a conductor 29 to the frame of the starter, which is electrically connected tothe line terminal 1 byi the conductor 2. l f. l

In Fig. 3, the parts are shown in normal When the switch S is closed, the core 20 )um sup, regardless of the quantity of current owing in the armature circuit; but the'core of the regulating solenoid. re-

`rnains in itsupper position until the quantity, `,of current m the armat re circuit falls to a predetermined quantit when 1 it drops,

rai-sion, 'a

therebyrocking theswitch arm V18, to closed current then lflows from conductor 2 to frame I), thence through switch arm 18, stationary' switch member 9, and conductor 1() to the armature, the solenoid C and start-ing rcsistance being shunted. When the line switch is opened, the core of the holding solenoid drops onto the lever and re-scts the starter as shown in Fig. 3.

I claim,-

1. In an automatic starter for electric motors, a starting resistance in the armature circuit, a regulatingsolenoid having windings in said circuit, a switch for cutting out said resistance and windings, said switch comprising a lever having one arm connected to the core of the regulating solenoid, and a holding solenoid having its core adapted to rest upon the opposite arm of the lever and to support the core of th'e regulating solenoid within its coils and the switch inv open position, said holding solenoid being arranged to lift its core and release the lever when the current is turned on.

2. `In an automatic starter for electric motors, a starting resistance in the armature circuit, a re ulating solenoid having its windings in sai circuit, a switch for short-cir- `cuiting said windings and resistance, said switch comprising a lever having one arm pivotallyconnected to the core of said solenoid and movable b y the Weight of said core to close the switch whenthe core is released from its coils, aholding solenoid having a heavier core than the core of said regulating solenoid said heavy core being adapted to rest loosely upon the oppositearmof said lever and thereby hold the switch in open position and the core of thev regulating solenoid in an up yer positionI when the current i`s turned o and said holding solenoid being adapted to move its coreupwardlyfrom the lever when the current is turnedon.

3. In an automatic` starter lfor electric motors, a starting resistance in the armature circuit, a regulating solenoid having its windmgs in said circuit, a switch for cutting out said resistance and windings, vsaid switch comprising a lever having one arm connected to the core of the regulating' solenoid, and a holding solenoid having its'windings in the armature circuit and having its core adapted -to bear upon the opposite arm ofthe lever and to support theA core of the regulatin solenoid in an upper position and the switc in open position, said solenoid being adapted.

to lift its core and release the lever when the current is turned on.

4. In an automatic starter for electric motors, a starting resistance in the armature circuit,V a regulating solenoid having its windings in said circuit, a switch for shortcircuitI ing said windings and resistance, said switch comprising-a lever havin one arm pivotally connected to the core o said solenoid and movable by the weight of saidvcore to. close `enigmi theswitch when the core is released from its y coils, a holding solenoid having its windings the armature circuit and having a core` heavier than the core of saidregulating solenoid, said heavier core being adapted to 'rest looseiy -u on the o posite arni of said lever and thereliny hold ti e switch in onen position and the core of the regulating so enoid in an 'Y 'up er position when the current is turned off,

an said holding solenoid being adapted to move its core upwardly from the lever when the current is turnedon.

5. inv an autorisatie starter for electric motors, a starting resistance in the armature circuit, a regulating devicel having windings insaid circuit and having a core or armature,

a switch ier cuttin out said 'resistance and windings, said switc i being connected to said core so as to nfiove therewith, an electromagnetic holding device having a core or armature, and connections between said cores whereby the core of-'the holdin device norinaliy .overbalances the core of t e regulating device and holds the switch in open position,

said holding device being arranged to lift its ycore from said connections when current is l turned on'.

6. In an automatic starter for electric motors, a starting resistance in the armature circuit, a regulating device having windings in said circuit and having a core or armature, a switch for cutting out said resistance and windings, said switch being connected to said core so as to move therewith, a lever pivotally connected to said core, an electromagnetic holdin device having a core or armature ada te to bear upon said lever'and to thereby iold the core or armature of the yregulating device inoperative relative to its coils and the switch in open position, said holdin device being arranged to lift its core and re ease the lever when current is turned on.

Iii testimony whereof l aiX my signature, in presence oi two Witnesses.

wiLLniM c. oBRiiiN.

Witnesses n ROBERT WATSON, CLAY JEWELL.

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