US1816454A - Control system - Google Patents

Description

July 28, 1931. H. WNWILLIAMS 1,816,454

CONTROL SYSTEM Filed March 24, 1928 WITNESSES INVENTOR Patented July 28, 1931 iii-siren rains iPjAfEENT"@FFECE HAROLD W. WILLIAMS, OF EAST PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WEST- INGHOUSE ELECTRIC 3 MANUFACTURING'COMPANY, A CORPORATION OF PENN- SYLVANIA CONTROL SYSTEM Application filed March 24, 1928i Serial No. 264,435.

This invention relates to motor control systems and more particularly to the control of direct current motors.

The object of the invention, generally '5 stated, is to provide, in a motor accelerating system, for effecting the actuationof a plurality of switches in a predetermined sequence to progressively short circuit sections of a starting resistor.

A more specific object of the invention is to provide for effecting the progressive operation of a series of accelerating switches independently of the current conditions prevailing in the motor.

It is a further object of the invention to provide for protecting the motor from eX cessive currents when the motor, after having been running in one direction, is reversed, causing it to operate in the other direction.

Other objects of the invention will become apparent when the following description is considered in connection with the accompanying drawing, wherein the single figure is a diagram illustrating the circuit connec- 25 Lions of the motor control system.

Referring to the drawing, a motor 1 is shown that comprises an armature 2 and a shunt field winding 3. A manually operable switch S is arranged to connect the control 30 scheme to the source of supply designated by the reference characters P and N. A manual- 1y operable master control switch C is used for controlling the directional contactors 4 and 5. whereby the direction of operation of 35 the motor may be determined.

To establish the operating circuit for the motor. the line switch S is closed and the master control switch C is moved either to the F position or the R position. Assuming 40 that switch S is closed and the master control switch C is moved to the F or forward position, a motor circuit is thus established from the conductor P through contact members 6 of the reversing contactor 4, the armal are 2- of motor 1, contact members 7, conductor 8. the coils 9 and 11 of the current limit relays 10 and 12. and resistor sections T3 to 16, inclusive, of the starting resistor 17 to the conductor N. Closure of the line switch S also establishes a circuit for the shunt-field 3 as is readily apparent from an inspection of thedrawing. The contact members 6 and 7 are obviously in circuit closing position because the closure of the master control switch C to the F position, caused the operation of the directional contactor 4 through the energization of the actuating coil 18 of the directional contactor 4. Obviously, if the switch C is moved to tbe R- position, the actuating coil 19 of the directional contactor '5 is energized and the contact members-2O a'nd2l are closed, thus establishing a inotor circuit for reverse operation. 7

As shown, the resistor 17 in this particular application of the invention is divided into four sections13, 14,15 and 16. In order to provide for shuntingthesesections, a plugging relay 22 and accelerating relays 23, 24 and 25 are provided. The purpose of resistor section 16 is to provide sufficient resistance in the motor circuit, in excess of that required for starting the motor from rest, to prevent excessive currents in the armature circuit when the motor is plugged, that is, when the voltage applied to the armature is reversed while the armature ofthe motor is rotating. 7 I

The contactor 22 normally operates whe the motor is started fromrest as its actuating coil 26 is connected in a circuit extending fron'i-linc COIiduCt r P l h'rough one portion of switch S the contact members of one of the reversecurrent relays'10 or 12. the actuating coil 26 and through a second portion of switch S to the conductor N. H The current limit relays 10 and 12 are biased to a circuit closing position by the-adjustable spring members 27 and 28 but are held against closing, when the directional contactors 4 and 5 are deencrgized or open, by the arm-like projections 29 and 2,0 disposed to engage the armatures of the current limit relays 12 and 10, respectively.

The coil windings 9 and 11 are so mounted on the relays that theirrespective magnetic effects oppose the biasing effect of the spring members 27 and 28, and the number of winding turns is so chosen that the contact members 81 and 32 will be in open circuit position when an excessive motor current passes entire resistor 17 maintainedin the armature tain the contact members 31 and 32 closed against the pull of the coils 9 and llwhen these coils are energized by a normal full load armature current or the normal current drawing by the armature during starting. HOW- ever, it is desirable that the relays 10 and 12' be actuated to their respective open-circuit positions before the current in the motor reaches a value of current which would .be drawn by the motor when it is pluggedi. Therefore, when the motor is plugged-, the relays will not close-until the current in the motor has fallen to a safe value, which will be the value at which the relay biasing springs 27 and 2Sover'come the efi'ect of the actuating coils 9 and 11. The value of current, above which the coils 9 and 11 will hold the contact members 31 and 32 open, may be varied by using adjustable springs or springs of (litterent strengths. The current limit relays 10 and 12 are constructed and adjusted to close contact members 31 and 32 with the respective operations ofthereversing contactors 4 and 5, when the motoriststarted from rest, and are prevented from closing when the motor is plugged until the motor current has fallen to a safe value. v

It will, therefore, be readily understood that when the motor-is plugged,-the plugging contactor 22 will be held open and the circuit of the motor until the current has fallen sufiiciently to allow one of the current limit relays 10 or 12 to close, depending'on which directional contactor has closed, and energize the actuating coil'26 of the coiltactor 22 which. when closed or energized, shunts the plugging resistor section 16 at the contact members 35.

The accelerating relays 23,2 and 25, which are employed for shunting the resistor secT tions 15, 14 and 13, res 'aectivelmare provided with actuating coils 36, 37 and 3.8; The actuating coils of these relays are energized by a circuit extending from line conductor P through the contact members of one the current limit relays 10 or 12, the coils 36, 37 and 38, which are connectedin parallel circuit relation with each other. through the contact members 39. 40 and 41of the time limit relays 42, 43 and 44, respectively, to the line conductor N. Consequently, the contact members 39, 40 and 41 must be closed, i. e., time limit relays 42, 43 and-44 must be energized before the corresponding accelerating contact members 45, 46 and 47 can be actuated to circuit closing position.

In order to control the operation of the timelimit relays 42, 43 and 44, a reactor 48 comprising an inductor coil 49 having a comparatively large number of turns wound on :1

Contact members of contactor 51 or contact members 56 line conductor N. I j he local closed series or discharge circuit for the rela "-actuating coils and the inductor coil49, which becomes active, when the contact members 55 and contact members 56 are of the plugging relay 22, to

opened,'t o'1naintain the current flowing in the circuit, comprises the actuating coils 52,

53,54, inductor coil 49','and a variable resistor 57, all of which-are connected in a closed series circuit with reference to the line conductors P and The variable resistor 57 tion, to the'inductorcoil'49 and the coils 52, 5.3 and 54 Consequently, when the energiz'ing circuit for the relay-actuating coils is interrupted by the opening'of'contact members 55 and 56, current will be maintained in the relay coils until the energy of the collapsmg'magnetic field'of the inductor. coil 49 has decreased to'a predetermined value.

The relays 42, 43 and 44 are normally biased to circuit making position by means of adjus'tablespring members 58, 59 and (30. These several springslmay be so adjusted that they will close the relays when different values oi current prevail in the circuit, The sanie rcsuit may be accomplished by adjusting the magnetic pull of th e several relay actuating coils by varyin th'e'numbcr of turns in the windings 'ofeacli coil, as shown. Because of these respective adjustin means, the timelimit relays may be made to operate in a definite sequence, and since their operation completes the energizing'circuits for the actuatmgcoils of the accelerating contactors 24 and25, respectively, the sections 15, 14. and 13 of resist-or 17 may be shunted in any desired order; and the motor brought up to s eed,

' Inthis application, after the closure of the contact members 47 of the accelerating contactor 25, its actuating coil 38 is maintained. energized by a bridging member 61 which is disposed on the armature of the contactor as iilustrated and completes a circuit in parallel relation to the resistor 17.

The auxiliary contactor 51, which, when not energized, provides one circuit for encrgizing thecoil 49 of the reactor 48 and for energizing the coils 52, 53 and 54, may have its actuating coil 62 connected across the en- 1S connected in shunt or parallel-circuit rela tire-1 resistor l7-and be cncrgizedlto open the contact members witlrthe .llUSt inrush of current to the motor. Since-the coi'itac't members 56 of the plugging relay'22 will open whenthe voltage is first applied to-the motor, the;energizing-circuit for the coil 49 is,*therefore, interrupted avhenvoltage is appliodto the-motor for starting. When the contact members 56 otthe plug-- ging relay22 and the contact'members 55 of the auxiliary contactor 51 are opened, the actuating coils 52, 53 and 54 of the time-limitrelays are energized'by current caused by the collapsing magnetic field of the inductor'coil 49, thus preventing the accelerating contac-v tors-.28,-24 and 2541- 111 operating to shunt sections of the resistor 17 The accelerating contactors will operate in'sequence, however, as thecurrentin theloopor local series cir-. cuit including .the reactor. coil 49 decreases, thus shunting the sections of the resistorl? in sequence and eausingthe motor to come up to speed. f j 1 -,When allithe contact membersi35, 45, 46 and-47. have closed and thejresistor 17 .is shunted,,the actuating- Icoil 62 v of the aux.- iliary contactor is deenergized, permitting the coi'itactmembers 55 to close. lVith-the contactor 51 deenergized, the actuating'coils of the time-limit relays 42, 43'and 44 will be reenergized to thereby cause the relays to be actuatedko their circuit-interrupting positions. lVhen, at this stage, the time-limit relaysare in theircircuit-interrupting positions, thegactuating coils 36 and 37- are' decnergized, thereby causing said switches to drop out, that is, open the contact members and 4G. The shunt circuit for the starting resistor isnot affected by these functions, since one of the current limit'relays, 10 or 12, still has its contact members closed. In consequence, the plugging relay '22-isj still energized and the accelerating relay 25 is energized by, reason of the holding circuit through the contact member 61.

The auxiliary contactor 51 is nowinjaposi: tion to effectanother operation of the accelerating relays or contactors when themotor is plugged. However, as the operating coil 38:0f the accelerating contactor 25 is maintained energizedby the bridging-or contact member 61, the resistor 17 -Wlll be maintained shunted until the circuit through the.eoils'..9 and ll of thc current limit relaysis interrupted by disconnecting the motor to stopor reverse the same. r I

In the system illustrated, the actuating coils of the directional contactors 4 and 5 are connected in circuits extending-from the line through one or the other-of the contacts of he master control switch O, depending on the direction in which the master switch is moved, one or the other of the actuatingcoils 18 or 19 to the conductor N, as illustrated.

ll' hen the line switch S is in the off position, the contact lnembers 55-of the auxiliary contactor-51 and the contact-members 56 of theplugging relay are.closed.- They also return to that position when the directional contactors 4 and 5 are-deenergized, Accordwill start to rotate whenreither contact mem- I hers 6;.and ,7 or contact members 20 and 21 arecaused to close as a result of the operation of the master controller C.

.i lVhen the -motor starts from rest, the current through the actuating coils 9 and 11 of the current limit relays lO and 12 will be insufficient ,tozhold the oontactmembers 31 and 32 open. :Accordi-ngly, ,a circuit is established throughone ortheotherof, these contact members," depending upon the direction of operationof-the motor,-for the actuating coil 26 ofthe plugging relay 22. The contact members ,35 are, therefore, closed to shunt the resistor-section 16. At the same time, thecircuitthrough contact members 56 is interrupted, thereby disconnecting the reactor coil 49 andthe time-limit relay actuatin'g coils, 52, 53 and-r54 from the :source of supply.- This aloneyhowever,does not interrupt 1 the circuit, through. the relay winc ings, sin'ceithe contact-members 55 of the auxiliary contactor 5l,are.disposed in the circuit. A, But; with the first flow of current through. the motor, oltage is impressed across the starting'resistor 17, thus energizing the actuating coil 62 of the-auxiliary contactor -51',and. thus causing the contact members 55 to open. lVith the above described operation ofthe auxiliary cont-actor 51, the reactor coil 49 and the coils ofthc accelerating relays-23, 24 and 25 are disconnected'from the-source of supply.

Immediately upon the disconnecting of the reactor coil 49' from theisource, the magnetic energy whichis stored-therein caused current to flow,,through the loop or closed series circuit, including the variable resistor 57, and the actuating coils otthe time-el ment relays 42, 43 and 44, causing them to hold their contacts in circuit-opening positions for a predetermined period. However, as the current gradually decreases, the re lays will close in a predetermined order, de pending upon the adjustments of the relays.

The period of time delay which is effected by the time-limit relays may .be varied considerablyby adjusting the;resistor 57 in the loop circuit. g l v In thesystem illustrated, the time-limit relay 42,.will operate first, causing the contactor23 to operateto shunt resistor section .15, then contactors 43 and 44 will operate in order, causing the contactors'24 and to shunt respective resistor sections14and 13 lVhen the accelerating contactor 25 operates the contact member 61 on this c'ontactor establishes a holding circuit for the actuating coil 38, whereby the contact members 47 Will be held closed to'maintain the resistor 17 shunted. Since the resistor'lf' is shunted by the contact members 47, the actuating coil 62 of the auxiliary contactor 57 will be deenergiz'ed. Upon the closing'ot switch 55, the reactor coil 49 and the time-limit relayactuating coils 52, 53 and'fit are again connected to the source of supply in order that conditions will'be in readiness for the next starting of the motor.

\Vhen the motor'is running at full speed in one direction and the motor is plugged, by reversing the voltage impressed on the motor, the current limit relays l0 and 12, as described before, will function to hold all the relays open, that is, tie-energized until the current in the motor circuit falls to such a value that one or'the other 01" the biasing springs 27 or 28 of the current limit-relays will effect the closure of one or the other of the contact members 31 01' 32.

Responsive to the closing of the contact members of the current limit" relays 10 or 12, the plugging relay 22 will shunt resistor section 16 and while this-is happening, the contact members of the contactor 51 are opened, but the circuit to the reactor coil 49 and the coils 52, 53 and 54 ot the time-limit relays are maintained energized untilthe contact members 56 are opened, that is, un'- til one or the other of the contact members 31 or 32 of the current-limit relays 10 and 12 are closed. Upon the opening of the contact members 55, the time-limit relays will function in the manner described heretofore. Since the inductor coil. 49 is provided with the core member 50 made of magnetic inatcrial, the magnetic energy that may be stored in the inductor coil may be of a relatively nigh value, thereby effecting a long time delay in operation of the relays.

lVhile I have described my invention in the preferred form, it will be readily understood that many modifications may be made thereof without departing from the scope of the invention, as defined in the appended claims. I claim as my invention: 1. In a control system, incombination, a plurality of switches, a separate relay for controlling the operation of each switch, a coil winding for each relay, an inductor connected to said coil windings, a circuit for energizing said inductor and'said coil windings, means disposed in shunt to said inductor and coil windings to provide a discharge circ'uit'for said inductor, and means for disconnecting the inductor and said coil windings from said energizing circuit, thereby permitting the energy stored in the inductor to be dis sipated through the relay actuating coils.

2. In a control system, in combination, a

series of relays, a coil for actuating each relay, an inductor and a resistor connected in loop circuit relation to said relay actuating coils, a source of electrical energy, means for connecting and disconnecting said inductor to said source for storing energy in the inductor, and means for adjusting the relays to respond to differentvalues of current flowing through their actuating coils to efiect their operation in sequence, when the inductor is disconnected from the source of energy.

In a control system, in combination, a source of energy,an electric motor, a resistor in circuit relation therewith, a plurality of accelerating switches for short circuiting section's-of the resistor, a plurality of relays for controlling the operation of the accelerating switches, an actuating coil for each relay and means for adjusting each relay to respond to different values of current in the actuating coils, an inductor connected in loop circuit relation with said actuating coils, means normally connecting said actuating coils and i nductor to said source, said means disposed to automatically interrupt said connection when the motor is initiall energized, permitting the inductor to be discharged to energize the relay coils for predetermined periods and to maintain: the relays in their open positions, said means subsequently re-establishing the connection of said coils and the inductor after the relays have eliected operation of the accelerating switches, and, means associated with one accelerating switch for holding itself closed to short circuit the resistor, after it has once closed.

4. In a control system, in combination, a source of energy, an electric motor, a resistor in series circuit relation therewith, a plurality of accelerating switches for short circuiting the resistor, a plurality of relays for controlling the operation of the accelerating switches, an actuating coil for each relay and means rendering said relays responsive to different current values flowing in the relay actuating coils, an inductor and a variable resistor for effecting a time delay in the deenergization of the relays, said inductor being connected in loop circuit relation with the relay actuating coils and the variable resistor, means for connecting the inductor and said relay coils to the source of energy, said means being automatically responsive to disconnect the inductor and said relay actuating coils from the source of energy with the first in-rush of current to the motor.

'5. In a control system, in combination, a source of energy, an electric motor, a starting resistor in series circuit relation therewith,

a plurality of accelerating switches for short,

circuiting the starting resistor, a plurality of relays for controlling the operation of the accelerating switches, an inductor for providing a time delay in the deenergization of the relays, a variable resistor for varying the period of delay, ana'ctuatingcoil'fo'r each-relay, the actuating coils being-"connected in loop circuit relation with thein'ductor {and the'variable resistor, means normally -'co'nne'ct ing the inductor and the relay actuating coils to the source of energyand means responsive to the'energization of"the 'mot'or' tor ldiscon necting the relay actuating coils from said source and allowing current fromthe "in ductor 'to energize the coils-and the variable resistor, and means i in the relays making them responsive. to the different current values in the loop ei'rciiitto effect the: actuation 'of the accelerating contactors i'n' jse quence as the current inf the 'ci rcuitfde '6. In acontrol system,'inicombinatidn,a source oi energy, a reversible electric motor, a starting resistor in' series circuit relation therewith, a plurality of acelefrating siiitches forfshort ,circuiti'ng said starting resister, a plurality of relays for controlling the operation of the accelerating an inductorior providing a time delay in the operation of the 'relays,'actuati ng "coils for the relays, a variable resistor -forvaryin the speed of operation o'ithe relays, aloop circuit inc'lu ding means I for determining the current conditions in the relay "actuating'coils which the tra s will beres'po'nsivetopper ate, 'a circuit ior connec ting the inductor across the source of I energy; when: the rnot or is first energized and means operatiye ?upon' the energization of the motor fordis'connecting the inductor from the source of energy, allowing it to dischargeits electrical'energy through the actuating coils ofthe' relays and the variable resistor, to control 'the"closure of the relays, maintaining them in theiropen circuit position until the current inthe loop circuit has fallen to a predetermined alue, a plugging switch for short circuiting a section of the re sistor andv means for'holding said plugging switch open until the current in the motor circuit has reached a predetermined value, said means preventing the interruption of the circuit through the inductor until said plugging switch has closed.

7. In a control system, in combination, a source of energy, a reversible electric motor, a starting resistor in series circuit relation therewith, a plurality of accelerating switches for short circuiting sections of the starting resistor, a plurality of relays for controlling the operation of the accelerating switches, an inductor for effecting a time delay in the operation of the relays, a variable resistor for varying the period of delay in the operation of the relays, a plurality of actuating windings for said relays, a loop circuit comprising the inductor, the relay actuating windings, and the Variable resistor, a plurality of means normally connecting the inductor, and the relay windings to the source of energy, said means being responsive to the current flowing in the motor "circuit for disconnecting said w-indings from the source of energy when the motoris-energized, allowing the inductor to discharge magnetic energy through" the relay actuating windings to efiectthe closing'of'the accelerating switches, means associated with one ofthe accelerating switches and effective upon the closure thereof for holdingit'closed to short circuit the'starting resistor, and means for delaying the interruption ofthemeans connecting the inductor and rela'ytofthe source of energy when the motor is 'be'ing plugged until the current; in the motor circuithas reached a predetermined condition. 1 al Ima'control-system, in combination, a source of energy, an electric motor, a starting'resis'tor, a plurality of switches 'forshort circuiting'sections of the resistor in progressive sequence, a-plurality of relays for controlling the' operation; of said switches, a plurality of actuating coils for-'eii'ecting'the operation-of said relays, an'inductor and a variable resistor disposed to providea time delay in the operation of the relays, a circuit for said relay actuating coils comprising the indu'ctor,"the Variable resistor, and said'actuating coi'ls, connected iii loop circuit relation,me ans for 'energi zin'g the inductor and the relay actuating coils when a' voltage is 7 applied to the motorg'and mea ns disconnecting *said energizing means allowing the current produced by the induction to maintain the relayactuating coils energized for a predetermined time to 'efi'ect a time delay in the operation of the resistor short circuiting switches" Z,'

'9. 'In a control system, in combination, a plurality of relays, an actuating coil for each relay, an inductor capable of storing magnetic energy for providing a time delay in the operation of the relays, said inductor being disposed in circuitrelation with said relay coils, a resistor connected in a circuit including'said resistor, said inductorand the relayactuating coils, means for energizing the inductor, and means for adjusting each relay to respond to a different current of a predetermined value flowing in said inductor.

10. In a control system, in combination, a series of relays, a coil for actuating each relay, an inductor connected in series relation to the actuating coils of said relays, a resistor connected in shunt relation to said actuating coils and inductor for regulating the discharge current of the inductor through said relay coils, means for energizing said inductor, and means for adjusting the relays to respond to different current values passing through their actuating coils.

11. In a motor-control system, in combination, a motor having a starting resistor connected in circuit relation therewith, a source of power for energizing the motor, a plurality of switches for shunting sections of the starting resistor, a plurality of relays for effecting the actuation of said switches, an ace tuating coil for each relay, an inductor, n 1eans connecting saidinductor in loop circuitmelation to said relay-actuating coils, electrorecircuiting said resistor, a relay that nor mally biased to its closed position and having a coil for effecting the operation of vsaid relay to its open position, a source, of energy for the system, an inductor connected in loop-circuit relation with the actuating coil of said relay, means for normally connecting said source, to the inductor, and means automatically .disconniectinglsaid inductor from said source when the, motor isenergized and for permitting the electrical energy stored therein to be dissipated through said relayactuating coil, whereby said relay may be held open until apredetermined current condition prevails in the loop circuit.

13. In a motor-controlsystem, in combina tion, an electric motor having a resistorcone nected in series-circuit relation therewith, a switch for short circuiting said resistor, a normally closed relay for effecting th-eoperation of said switch, an actuating coil for said relay, an inductor connected in loopcircuitrelation with said relay-actuating coil for providing a time delay in the operation of the relay when the motor is being started, means for energizing the inductor to thereby cause said'relay to be actuated to its open position when the motor is energized, means for automatically disconnectingthe inductor -from the source, means connected in circuit relation to said inductor and actuating coil and disposed to cause said inductor to dissipate its magnetic energy in the actuating coil of the relay when the inductor is disconnected from said source, and means for adjusting the relay so that it will close to effect the operation of the resistorshort-circuiting switch when a predetermined condition prevails in the loop circuit.

1%. In a control system, in combination, a source of energy, an electric motor, aresistor in series-circuit relation therewith, a pinrality of accelerating switches disposed to short circuit sections of the resistor, a relay for controlling the operation of each accelerating switch, an actuating coil for each re lay, and means disposed to e'fl ect seqrzential to again close to effect sequential operation of the accelerating. switches, and means disposed tore-energize said relay coils and in-. ducton whenthe motor has been fully acceleral V v I Q 15. In a control system, combination, a source of energy, areversible electric motor and a starting resistor in series relation therewith, a plurality of switches for short clrcuit ng sections ,ot the starting. resistor, means responsive to: the current I conditions in the motor for closing one of said switches, said means being disposed to hold the switch open for a predetermined period after the motor. is pluqged, a plurality of relays each proYided wita'actuating coils for controlling the operation of the other. resistor-sliort-circuiting switches, and/means for gra c lually increasing the current in said coils for ellecting operation, ofqsaQd relays in progressive succession independently of the current conditions in the motor, said means comprising saidactuatingcoils, tin-inductor coil and a variable resistor connected. in loop-circuit relation, means for connect-ing said inductor cpil and said relay-actuating coil in seriesc1rcu1t relation. across, the source of: energy when said motor isjconnected to said source of energy, means for-disconnectingsaid loop circuit from the source of energy when the motor is firststarted, and means foi' proventing operation of said, disconnecting means when 'the mojtor is plugged until predetermined current condition prevails in the motor. i I

In testimony whereof, I have hereunto subscribed my name this 20th day of March,

HAROLD W. WILLIAMS.

Images