US1421180A - System of control - Google Patents

Description

R. E. 05 CAMP." SYSTEM OF CONTROL.

APPLICATION FILED MAY12, 1919.

Patented June 27,- 1922.

2 SHEETSL-SHEET 1 29 WITNESSES: P giggam X, i Y B UNITED STATES PATENT OFFICE.

BAY E. DE CAMP, or wILII NsBURG, PENNSYL ANI ASSIGNOR TO WESTINGHOUSE ELECTRIC a; MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

'sYsrE or CONTROL.

To all whom it may concern:

Be it known that LRAY E. DE CAMP, a citizen of the United States, and a resident of Vilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Systems of Control, of which the following is a specification.

My invention relates to systems of control of general application but more particularly to systems for controlling electric motors such, for example, as motor-accelerating systems involving main switches or contactors designed to close in succession to shunt a resistor.

In a co-pending application by H. D. James, Serial No. 236,937, filed May 27, 1918, and assigned to the Westinghouse Electric & Manufacturing (10., is disclosed a motorcontrol system in which relays, of the type constituting the subject-matter of my copending application, Serial No. 241,259,1iled June 21, 1918, for closing the contactors are controlled by a coil in parallel circuit with the accelerating resistor. Ina co-pending application by H. D. James, Serial No. 27 0,- 147, filed January 8, 1919, and assigned to the above-named company, is disclosed a motor-control system of the same general type in which the relays of the same type are controlled by a coil in series with the accelerating resistor.

The object of my present invention is to provide an improved system of the abovedesignated'character and an improved relay for use in such system.

According to the present invention, several of the relay armatures illustrated and described in my above-named application are provided with additional controlling coils that are connected between points of different potential, thereby insuring the se quence of operation of the relays, as will be made clear hereinafter.

In the accompanying drawings, Figs. 1 and 2 are, respectively, a side elevation and a front view of my improved relay; Fig. 3 is a diagrammatic view of circuits and apparatus embodying the relay of Figs. 1 and 2,

the controlling coil being connected in parallel circuit with the resistor; Figs. 4 and 5 are similar views of systems, in which the controlling coil is in series with the resistor,

Specification of Letters Patent. Patented J n eq" 1922 Application filed Kay 12,

1919. Serial NO. 296,601.

and Fig. 6 isa similar view of an alternating-current motor-control system embodying my inventlon. Referring first to Figs. 1 and 2, an insulatlng panel 29 carries two brackets 30 and 31 supporting coils 22 and 23 which,-when energized by current flowing through them, pro duce magnetic fields for attracting an armature 32 and any desired numberof addi* tional armatures 33, 34 and 35. A compression spring36 is adjustably mounted upon a nonmagnetizable rod 37 that is slidably mounted in arms 38 and 39, which are rigidly connected to, or constitute integral parts of, the bracket 31. l The projection 38 serves also as a pole piece for the armature 32, and the projection 39 as a pole piece for the armatures 33, 34 and A bar 40 is rigidly connected to the rod 37 and normally engages the armatures 33, 34 and 35. The spring 36 thus normally maintains the armatures 33, 34 and 35 in their open positions, with the members 41, which are carried by these armatures, in contact with the pole piece 39. The members 40 and 41 are preferably composed of non-magnetizable niaterial to prevent freezing.

The armature 32 is provided with ears or lugs 42, which are pivotally mounted upon the bracket 30, and is normally maintained in Contact with one end of the rod 37 by a Weak spring 43. The bracket 30 supports a nonmagnetizable, U-shaped member 44, between the arms of which are pivotally mounted'the armatures 33, 34 and 35which carry, respectively, the movable contact members 45, 46 and 47 of relays 25, 26 and 27. The corresponding stationary contact members 48, 49 and 50 are mounted upon the insulating panel 29.

Springs 5lare attached to longitudinally adjustable members 52 and to the other ends of the members 41. The pole piece 39 is provided with longitudinally adjustable members 53 to. regulate air gaps 70 between A bracket 71, mounted upon the insulat ing panel 29, supports two coils 77 and 78 each having a pole piece 79 for attracting the armatures 3 1 and 35.

Referring now to Fig. 8, a motor, which may be of the series or compound-wound type, the shunt-wound type being here illustrated, having an armature 1 and a shunt field-magnet winding 2, is connected between line conductors 3 and 1, separated by a line contactor 5, with an accelerating resistor 6 in series with the armature 1. A master switch 7 is adapted to ellect the closing of the line contactor 5, through an energizing coil 8, upon making contact with contact members 9 and 9a. A plurality of contactors 10, 11 and 12 are adapted to effect the short-cireuiting of sections 13, 1 1 and 15, respectively, of the resistor 6, when the master switch 7 occupies succeeding positions, in which it engages contact members 16, 17 and 18, which respectively control the circuits of the actuating coils 19, 20 and 21 of the contactors 10, 11 and 12. The coil 22 is connected across the accelerating resistor 6, and the coil 23 is adapted to be connected to the line conductors 3 and 4 upon the closing of the relay 2?. The coil 77 is connected across the resistor section 13 but. is adapted to be short-circuited upon the closing of the contactor 10. The coil 78, similarly, is connected across the resistor sections 13 and 1 1 but is adapted to be shortcircuited upon the closing of the contactor 11.

Upon the actuation of the master switch '7 to its first position a, a circuit is established from the line conductor 3 through the coil 8 and the contact members 9 and 9a, to the line conductor 1. The line contactor 5 becomes thereupon closed to establish the motor circuit, which extends "from the line conductor 3, through the line contactor 5, the armature 1 and the resistor 6, and the shunt field-magnet winding 2, in parallel, to the line conductor 4. The coil 22 becomes thereupon energized by the voltage drop of the resistor 6. As the motor accelerates and this voltage drop, in consequence, de creases, the influence of this coil 22 over the armatures 33, 34 and 35 becomes lessened. After a time, the armature is closed by its spring 51 (Fig. 1) establishing the engagement of the contact members 41-5 and 46 of the relay 25.

It, now, the master switch be actuated to its second position b, a circuit will be estab lished from the line conductor 3, by way of a conductor 28, through the relay 25, the coil 19 and the contact members 16 and 9a to the line conductor 4. The contactor 10 will thereupon close to elli'ect the short-circuiting ot the resistor section 13.

So long as the resistor section 13 remains in circuit. with the armature 1, the armatures 34 and 35 are maintained open by the magnetism 01" the coil 22 and of the coils 77 and 78, respectively. Upon the short-circuiting of the resistor section 13, the coil 77 is deenergized, the coil 78 remaining energized, but this coil is now subjected to the voltage drop across the resistor section lat only. The arn'iature 34: remaining now under the inl'luence oi the coil 22, will ultimately become closed, in accordance with the decreasing voltage drop across the resistor 6, to effect the engagement of the contact members 16 and 19 ot' the relay 26. It the master switch 7 be now actuated to the third position 0, a circuit will be established from the line conductor 3, by the conductor 28, tlnough the relay 26, the coil 20 and the contact members 17 and 9a to the line conductor 4-. The contactor 11 thereupon closes to e'll'ect the short-cincuiting ot the second re sistor section 1%..

Upon the short-circuiting ot the resistor section 1 1, the coil 78 becomes short-circuited and the armature 35 remains under the influence of the coil 22 only. As the motor continues to accelerate, and the voltage drop of the resistor 6 decreases, in consequence, the armature will ultimately be closed by its spring 51 (Fig. 1) to effect the closing of the relay 2?, whereupon, assuming the master switch 7 to occupy its final position (1, a circuit is established from the line conductor 3 by way of the conductor 28, through the relay 27, the coil and the contact members 18 and 90 to the line conductor *1. The contactor 12 becomes thereupon closed to effect the short-circuiting ot' the remaining section 15 oil. the resistor 6, whereupon the armature 1 becomes connected directly across the line conductors 3 and 4t.

The short-circuiting oil? the entire resistor 6 effects the de-energization of the coil. 21., but the armatures to 35, inclusive, (Fig. 1) remain in their actuated positions because of the influence of the coil 23, which becomes energized upon the closing of the relay 27 by a circuit extending from the line conductor 3, by the conductor 28, through the relay 27 and the coil 23, to the line conductor 1-. The motor, therefore, may continue to operate at maximum speed until the Inaster switch 7 is actuated in the opposite direction to any one of the positions, a, Z) and c.

l ilthough the operation has been described upon the supposition that the master switch 7 is actuated step-by-step, it will be obvious that the master switch 7 may be actuated to its final position (Z in a single step. in which event, the above-described operations will take place automatically and in the desired sequence.

If the master switch be now actuated in the opposite direction to the position 0, the abovedescribed circuit oi the coil 21 becomes broken at the contact member 18. The contactor 12 thereupon becomes opened by gravity to effect the reinsertion into the armature circuit of the resistor section 15. If the master switch 7 be actuated to the position 5, the circuit of the coil 20 becomes open at the contact member 17, whereupon the contactor 11 falls open by gravity to effect the reinsertion of the resistorsection 14 into the armature circuit. The coil 78 becomes thereupon subjected to the voltage drop of the resistor sect-ion 14, whereupon it effects the opening of the armature 35 of the relay 27, This, in turn, breaks the circuit of the coil 23, but the coil 22, being now subjected to the voltage drop across the resistor sections 14 and 15, will maintain the armature 32 (Fig. 1) in its actuated position. If, now, the master switch 7 be returned to the position a, thecircuit of the coil 19 becomes broken at the contact member 16, whereupon the contactor 10 drops open to effect the reinsertion into the armature circuit of the resistor section 13. The coil 77, becoming thereupon subjected to the voltage drop across the resistor portion 13, effects the opening of the armature 34 of the relay 26. I11 this manner, the sequential operation of the contactors 10, 11 and 12 and the relays 25, 26 and 27 is insured. Without the aid of the coils 77 and 78, the armatures 33, 34 and 35 are likely to be opened during deceleration in some other sequence than that desired if, indeed, they are opened at all until after the return of the master switch 7 to the illustrated off position.

The employment of the coils 77 and 78 is especially desirable when the coil 22 is so designed that the armatures 33, 34, and 35 operate at values of the magnetism of the coil 22 which are close together. If these values are far enough apart, the coils 77 and 78 may be dispensed with. Indeed, one of the chief advantages of connecting the coil 22 across the resistor 6 is that it is possible to design the coil 22 so that the relays 25, 26 and 27 will be closed at values of the magnetism of this coil, which are substantially different. This is not true, however, when the coil 22 is connected in series with the resistor 6, as will be made evident by reference to the above-mentioned application of James, Serial No. 270,147. Special care must be exercised in designing the coil 22 so that the armatures 33, 34 and 35 will be actuated at the proper time in accordance with the motor deceleration. The use of my coils 77 and 78, connected in the fashion above described, or some similar fashion, is therefore particularly advantageous when the coil 22 is connected in series with the resistor 6.

This will be made clear from a study of Figs. 4 and 5, in the former of which the coils 77 and 78 are omitted and in the latter of which these coils are employed. In both these figures. the master switch 7 of Fig. 3 is replaced by one of more simple the accelerating resistor 6, but inseries therewith. In the system of Fig. 4, however,

the coils 77 and 78 are not employed, where-,

as, in the system of Fig. 5, where these coils are made use of, the coil 23 is omitted, its function, to some extent, being performed by a switch 23 which is mechanically connectedto the contactor 12 so as to be closed simultaneously therewith. In other respects, the apparatus andthe connections are very similar to those of Fig. 3. 1

The operation of Fig. 4 will be readily understood from the description of Fig. 3. The relays 25, 26 and 27 are successively closed by their actuating springs 51 (Fig. 1) in accordance with decreasing values of the magnetism of the coil 22. Upon the closing of the last relay to close, 27, not only is the contactor 12 closed thereby, but the coil 23 becomes energized as well. This precaution is advisable because, though the series coil 22 does not become short-circuited in the system of Fig. 1, its effect becomes, nevertheless, so weakened that it is well to have the additional influence of the coil 23 which is, at that time. connected across the line con ductors 3 and 4.

The disadvantage of the system of Fig. 4 is that the values of the magnetism of the series coil 22 are so nearly alike that the relays 25, 26 and 27 must be set to operate at values so close together that there is danger of improper operation. The system of Fig. 4, therefore, in the form shown, is less desirable than that shown in Fig. 5, in which the coils 77 and 78 are employed.

In the system of Fig. 5, upon the closing of the master switch 7 to effect the energization of the coil 8, the line contactor 5 becomes closed to established the motor circuit from the line conductor 3, through the contactor 5, the series coil 22, the armature 1 and the resistor 6, and the shunt field-magnet winding 2, in parallel, to the lineconductor 4. The coil 22 becomes accordingly energized to actuate the armature 32 (Fig. 1), whereupon the armatures 33, 34 and 35 become released from the restraining influence of the spring 36. Initially, the current is too high to permit the springs 51 to close their armatures, but, as the motor accelerates, the current value decreases. When the current falls to a predetermined value, the relay 25 will become closed by its spring 51 to effect the closing of the circuit of the coil 19, the consequent closing of the contactor 10 and, therefore, the short-circuiting of the resistor section 13.

The simultaneous, or the nearly simultaneous, closing of the relays 25, 26 and 27 is, however, prevented by the coils 77 and 7 8, the former of which, being connected across the resistor section 13, aids the coil 22 in maintaining the relay 26 open and the latter of which,being connected across the resistor sections 13 and 14, aids the coil 22 in maintaining the relay 27 open. Upon the shortcircuiting of the resistor section 13, the coil 77 becomes short-circuited and the coil 78 becomes subjected to the influence of the voltage dropacross the resistor portion only. Before the relay 26 may become closed, however, the motor current rises to a higher value, following the short-circuiting operation of the resistor portion 13, whereby the coil 22 is enabled to maintain the relay 26 open until the current drops again to a lower value. The relay 26 then becomes closed to effect the energization of the coil 20, the resulting closing of the contactor 12 and the consequent short-circuiting of the resistor section let.

The relay 27 is maintained open at this time, however, by the coil '78, which is subjected to the voltage drop of the resistor section 14; until this resistor section has become short-circuited, whereupon the motor current again rises, whereby the coil 22 exerts an increased magnetic force upon the armature 35 of the relay 2?, so that this relay is not permitted to close until the motor current again drops to a sulliciently low value. In this manner, the successive closing of the relays 25, 26 and 27 and the consequent short--circuiting of the resistor sections 13, 14 and 15 are assured.

The closing of the contactor 12, besides effecting the short-circuiting of the resistor section 15, establishes also a circuit from the line conductor 3, by the conductor 28, through the switch 123 and the coil 21, to the line conductor 4t, so that the contactor 12 is maintained closed without the aid of the relay 27, so that, when the motor finally reaches normal, maximum speed, when the series coil 22 becomes too weal: to maintain the armature 32 and the spring-pressed rod 37 (Fig. 1) in actuated position, the relays 25, 26 and 27 may become opened without in any way afi'ecting the continued operation of the motor. The switch thus replaces the coil 23 of Fig. 4:. When it is desired to stop the motor, the master switch 7 may be opened to effect the opening of the contactor 5, at which time a second switch 87. that is mechanically connected thereto, becomes opened to effect the de-energization of the control circuits, notably the circuit of the coil 21.

.My invention may be applied also to alternating-current motors, as will be made clear by a study of the system of Fig. 6. The primary winding 62 of an alternating-current motor is connected through a three pole contactor 5 to line conductors 3a, 3?) and 30,

which are connected to any suitable source of alternating current, the contactor 5 being adapted to be closed by an actuating coil 8, which is connected to any two of the conductors 3a, 3?) and 30, through a master switch 7. The secondary winding 63 is sup plied with an accelerating resistor 6, sections 13, 14- and. 15 of which may be successively shortcircuited by the contactors 10, 11 and 12.

The relay structure of Figs. 1 and 2 may be modified in any suitable manner to adapt it for employment in connection with alternating-current motors. The coil 22 may, however, be connected in series with one of the primary conductors 3a, 3b and 30 (or even one of the secondary conductors) in which event, the coils 77 and 78 play an important function, as in the system of Fig. 5. The coils 77 and '78 may be connected across the resistor section 13, and and 14, rpspectively, as in the case of Figs. 3 and 5, but, smce the voltage drop between pairs of the secondary conductors 1a, ib and 40 decreases with an increase in motor speed, I have shown the coils 77' and 78 as connected across two of the secondary conductors ia and do at the junction points of the resistor sections 13 and 1 1, and 14: and 15, respectively.

Upon the closing of the contactor 5, the primary winding 62 becomes energized, whereupon current is induced in the secondary winding 63 and flows through the resistor 6.

The coil 22 becomes energized by the current in the primary conductor 30, which, falling in value with increase in motor speed, permits, after a time, the closing of the armature 33 of the relay 25 by its spring 51 (Fig. 1). A circuit becomes then established from the primary conductor 360 by the conductor 28, through the relay 25 and the coil 19, to the primary conductor 30. The contactor 10 becomes thereupon closed by its energizing coil 19 to effect the shortcircuiting of the resistor portion 13.

The armatures 34-. and 35 of the relays 2-6 and 27 are maintained open, however, as in the case of the system of Figs. 3 and 5, by the coils 77 and 78. Upon the short-circuiting oi": the resistor section 13, the coil 7 7 becomes short-circuited, but not until after the motor current has increased, following the short-circuiting of the resistor section 13. As the motor speed continues to increase and. the primary current value to decrease, in consequence, the armature 34 is permitted to close, whereupon the relay 26 closes to effect the energization of the coil 20, the resulting closing of the contactor 11 and the consequent short-circuiting of the resistor section 1. 1.

The relay 27, however, is still maintained open by the coil 78, which becomes shortcircuited with the closing of the contactor 11 with the resulting increase in value of the current traversing the motor circuit, so that the coil 22 is enabled to maintain the armature open. The armature 35 closes in the manner described in connection with armature 84 to eitect the closing of the contactor 12 and the short-circuiting of the resistor section 15. The switch 123 performs the same function as described in connection with the system of Fig. 5.

Modifications will readily occur to those skilled in the art and are intended to be covered by the appended claims.

I claim as my invention:

1. The combination with an electric motor havin a resistor associated therewith, of a plurafity of switches for controlling said resistor, a coil in circuit with said motor for controlling all of said switches, and a second coil connected across points of said resistor for controlling one only of said switches.

2. The combination with an electric motor having an accelerating resistor, of a pair of switches for short-circuiting successive sections of said resistor, each having an actuating coil, a pair of relay members, one for each of said switches, having a controlling coil across said resistor, the second of said relay members to operate having a second coil connected across the section of said resistor that is adapted to be first short-circuited, and a switch for successively controlling said actuatin coils.

3. The combination wit an electric motor having an armature and a resistor in series therewith, of a pair of switch members for effecting the short-circuiting of successive sections of said resistor, means for controlling said switch members comprising a coil in circuit with said armature and having series characteristics, the second of said switch members to operate having a second coil connected across the section of said resistor that is adapted to be first shortcircuited.

a. The combination with an electric motor, a source of energy for said motor, and a resistor in circuit with said motor, of a pair of switches for shortcircuiting said resistor and having a common controllin cOil in circuit with said motor, each of said switches except the first to close having a second coil controlled in accordance with the effective portion of the resistor that is effective.

5. The combination with an electric motor having a resistor associated therewith, of a pair of switches for short-circuiting suc cessive sections of said resistor, a pair of relay members, one for each of said switches, having a controlling coil in circuit with said motor and the second of said relay members to operate having a second controlling coil connected between points of said resistor, and means for maintaining the second of said switches to operate in operative position.

In testimony whereof, I have hereunto subscribed my name this 26th day of April, 1919.

RAY E. DE CAMP.

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