US1175321A - System of electric-motor control. - Google Patents

Description

Tx VARNEY.

SYSTEM OF ELECTRIC MOTOR CONTROL.

APPLICATION FILED AUG. I2, 1912.

2 SHEETS-SHEET 1.

Patented Mar. 14, 1916.

ATTORNEY THE COLUMBIA PLANOGRAPH co WASHINGTON. D. C-

T. VARNEY.

SYSTEM OF ELECTRIC MOTOR CONTROL.

APPLICATION FILED AUG. 12. 1912.

1,175,321. Patented 1m. 14, 1916.

Z SHEETS-SHEET 2.

WITNESSES: INV TOR l ATTORN EY ms COLUMBIA PLANOGRAPH 110., WASHINGTON, D. c.

THEODORE VARNEY, OF PITTSBURGH, PENNSYLVANIA,

ASSIGNOR TO VJ'ESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

SYSTEM OF ELECTRIC-MOTOR CONTROL.

Application filed August 12, 1912.

To all whom it may concern:

Be it known that I, THEODORE VARNEY, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Systems of Electric-Motor Control, of which the following is a specification.

My invention relates to systems of electric motor control and it has special reference to such systems as embody a plurality of structurally independent switches that are adapted to close in a predetermined sequence.

The object of my invention is to provide a system of the character above specified that shall be simple in arrangement and positive and effective in operation. 7

Control systems embodying a plurality of independently operated magnet switches have sometimes been made dependent upon the counter-electromotive force generated in the motor armature, in order to insure their closing in a predetermined sequence.

According to my present invention, I provide a series of accelerating switches of the so-called lock-out type which have the characteristic of remaining open, provided their coils are energized above a predetermined value, and of closing automatically when the energy falls below said predetermined value.

Instead of providing each switch with a series coil, in accordance with the usual arrangement, I provide the switches with shunt or separately excited coils which are normally energized to lock the switches in their open positions and, in addition, I provide opposing coils which are relatively weak and are dependent upon the counterelectromotive force generated in the motor armature. The opposing coils are so proportioned as to partially neutralize the effect of the shunt coils and to permit the shunt coils to close the switches in succession.

My invention is illustrated in the accompanying drawings, in which Figures 1 and 2 are diagrammatic views of different control systems embodying my invention. Fig. 3 is an elevation of a preferred form of switch adapted for use in the systems shown in Figs. 1 and 2. Fig. 4 is a partially diagrammatic view of a modifica- Specification of Letters Patent.

Patented Mar. 14, 1916.

Serial No. 714,555.

tion of my invention in which the switches are pneumatically operated and electromagnets are employed for governing the valves through which air is admitted to actuate the switches.

Referring to Fig. 1 of the drawings, the system here shown comprises anelectric motor 1 having anarmature 2, a field magnet winding 3, a resistor a, aline switch 5, a plurality of acceleratingswitches 6, 7 and 8 and amaster switch 9. Theswitches 6, 7 and 8 preferably have the structural characteristics shown in Fig. 3 to which reference will now be had. The switch here shown comprises a stationary base or face plate 11, to which astationary contact member 12, U-shapedstationary core member 13 and a bracket ltt are secured,coils 15 and 16, amagnetizable armature 17, which is pivotally supported on the bracket 11 and a movable contact member 18 which is carried by the armature. Thearmature 17 is adapted to bridge thecore member 13 when the switch is closed, and is provided with aprojection 19, which is substantially parallel to thelower branch 20 of the stationary core member when the switch is open. The end of theprojection 19 is spaced from the stationary core member by an adjustingscrew 21 which determines the air gap existing between the members. Thebranch 20 is smaller in cross sectional area than the body of the core member and, when the flux produced by the coils l5 and 16 is sufficient to saturate thebranch 20, the excess traverses theprojection 19 of the armature and holds the switch in its open position.

Assuming that switches of this character are utilized in the system shown in Fig. 1, the operation of the system is as follows: If themaster switch 9 is closed. a circuit is established from aterminal 22, through aconductor 23 and a contact finger 24: to acontact member 25 of theswitch 9. From this point, one circuit is completed through acontact finger 26. acoil 27 of theline switch 5 and aconductor 28 to the opposite terminal 22 A second circuit is completed fromcontact member 25, through afinger 29,shunt coils 32, 31 and 30 of theswitches 8, 7 and 6 toterminal 22*. Theswitches 6, 7 and 8 are respectively provided withcoils 33, 34 and 35, which are connected in series circuit relation to each other and in shunt circuit re lation to thearmature 2 of themotor 1. WVhen thecoils 30, 31 and 32 and thecoil 27 are first energized, no energy is supplied to thecoils 33, 34: and 35, inasmuch as the motor is at rest. The energy suppliedto thecoils 30, 31 and 32 is suflicient to lock open theswitches 6, 7 and 8, as already described, and thecoil 27, when energized, closes theline switch 5. A circuit is consequently established from theterminal 22, through theswitch 5,armature 2, field magnet winding 3 andresistor 4 toterminal 22 The motor is thus supplied with energy, and the entire accelerating resistor d is included in circuit. As soon as the motor acquires a predetermined speed, its counter-electromotive force so energizes thecoil 33, in opposition to thecoil 30 ofswitch 6, as to reduce the flux traversing thestatlonary core member 13 until thebranch 20 is able to carry it without saturation. The flux which predominates in its action upon thearmature 17 1 therefore closes the switch. Theswitch 6,

when closed, short circuits a portion'of the resistor 4:, in the usual manner, and the motor is still further accelerated. The coils 34: and 35 are so proportioned relative to thecoils 31 and 32 as to require a progressively increasing counter-electromotive force in order to permit the switches to close. It is therefore evident that the three switches will be closed in succession with an interval between successive operations which will be dependent upon the load and the rate of acceleration of the motor. The switches, when once closed, will remain closed until themaster switch 9 is thrown to its open position. It will be observed that the switches are provided with main contact members only, no interlocks or auxiliary contacts being required to insure their successive operation.

Fig. 2 is similar to Fig. 1, except that thecoils 33, 3 1 and 35 are arranged in multiple circuit relation and are dependent, for their circuit connections, upon amaster switch 36 that is substituted for theswitch 9. In this arrangement, the master switch is provided theterminal 22, through a conductor 37 and acontact finger 38 to contactmembers 39. From this point, one circuit is completed through acontact finger 40, aconductor 41, thecoil 27 ofline switch 5 and aconductor 42 to the terminal 22 A second circuit is completed through a finger 43, a conductor 44:, thecoils 32, 31 and 30 in succession and aconductor 45 to theterminal 22 of theline switch 5. Thecoils 30, 31 and 32 are thus energized as in Fig. 1, theswitches 6, 7 and 8 being locked open. Theline switch 5 is closed by reason of the energization ofcoil 27, and the motor circuit is established as before. The acceleration, however, is not automatic and theresistor 4 will remain in the motor circuit until themaster switch 36 is advanced to occupy its successive positions Z), c and (Z. Thecoils 33, 34 and 35 will then be successively included in multiple relation to each other in a shunt connection to thearmature 2 of the motor. As each coil is included in this circuit, it sufficiently opposes the action of the other coil of the switch to permit the switch to close. In order to stop the motor and open the switches, it is only necessary to throw the master switch to its 05 position.

Referring to Fig. 4: of the drawings, theswitches 5, 6, 7 and 8 are respectively actuated by a plurality ofpistons 45, 46, 47 and 4.8 which act incylinders e8 419, 50 and 51. Pneumatic pressure is supplied from a tank orreservoir 52, through apipe 53,valves 53, 54, 55 and 56, andpipes 56*, 57, 58 and 59 to the cylinders. Thevalve 53*, which governs theswitch 5, is controlled by ama gnet 68 having acoil 69 which, when energized, opens the valve in opposition to gravity or a. spring, in a well known manner, and admits air through the valve to the cylinder 18*. Each of thevalves 54, 55 and 56 is provided with a valve magnet having amovable core member 61 to which astem 60 is secured. The valve magnet further comprises astationary core member 62, and coils which are designated by reference characters corresponding to the actuating coils of theswitches 6, 7 and 8 of Figs. 1 and 2. Thestationary core member 62 of each valve magnet comprises ashell 63, amagnetizable sleeve 64 through which themovable core member 61 operates, in addition to the body of the core member to which the movable member is attached. Thesleeve 64 is provided with abushing 65, of non-magnetizable materiahwhich provides a material air gap between aprojection 66 of the movable core member and the sleeve. A slightly larger air gap is provided between the body of themovable core member 61 and the end of thesleeve 64, so that, under normal conditions, when the magnet is energized below a. predetermined value, the flux traversing the stationary and movable members tends to open thevalve 56. If, however, the magnet is energized above a predetermined value, theprojection 66 of the movable core member becomes saturated and the flux passes directly from thebody 61 across the air gap into the sleeve 64:, producing such an attraction between these members as to prevent movement of the core member (31 and the opening of the valve. The valve magnet operates in accordance with well known lockout switch principles and serves to hold the valve closed it energized above a predetermined value and opens the valve as soon as the energy has decreased to said value.

The operation of this system is as follows: Assuming that the valves are closed, as shown in the drawing, and that the switches are open, if themaster switch 67 is closed, a circuit is established from alineconductor 70 through contact fingers 71, which are bridged by contact segments 72 of the master switch,resistor 73, aconductor 74, arelay switch 75, which is normally closed, a conductor '76, thecoil 69 or" thevalve net 68 and a conductor 7.7 toopposite line conductor 78. Another circuit is also established from theconductor 75, through thecoil 30 of thevalve magnet 5%, thecoil 31 of thevalve 55 and thecoil 32 of thevalve 56 to the conductor 77. hen the master switch is closed, another local circuit is established from oneterminal 79 of themotor armature 2, through aconductor 80, a control conductor 81, contact fingers 82 which are bridged bycontact segments 83 of the master switch, aresistor 8%, aconductor 85, thecoils 35, 3e and 33 of themagnets 56, 55 and 5e and aconductor 86 to anopposite terminal 87 of the motor armature. Thecoil 69, when energized, immediately opens thevalve 53 and admits air to thecylinder 48 thereby closing theline switch 5. Although thecoils 33, 34- and 35 are connected across the terminals of the motor armature, no current is supplied to them until the motor accelerates sui'iiciently to build up its counter-electromotive force.

Thecoils 30, 31 and 32 are suliicientl ener- I gized to magnetically saturate thearojections 66 of the movable core members of the magnets associated with thevalves 5 55 and 56 and to lock the valves in their closed positions, as hereinbefore explained.

When theline switch 5 is closed, a main circuit is completed from theconductor 70, through theline switch 5, the resistor l, aconductor 88, the field magnet winding 3, the armature 9., the conductor and a coil 89 of the relay switch 7 5 and the conductor 77 to the opposite line conductor 7 8. As the motor accelerates and its counter-electrometive force increases, thecoils 33, 34 and 35 will be increasingly energized, their design being such that thecoil 33 first exerts such an influence, in opposition to thecoil 30 of the same magnet, as to reduce the fiuX until theprojection 66 of the core member is able to carry it without saturation. Under these conditions, the leakage flux which held the valve closed is very much reduced or is entirely overcome and, consequently, the valve is opened. The opening of thevalve 5 1 admits fluid pressure to the cylinder l9, thereby causing theswitch 6 to close and to short circuit a portion of theresistance 4. As the motor continues to accelerate, the coil 3i and tien thecoil 35 are successively energized to a sutlicient degree to permit the opening of thevalves 55 and 56. As these valves are opened, theswitches 7 and 8 are closed and the resistor a is shortcircuited. If the current traversin the motor circuit becomes excessive, tie coil 89 of therelay switch 75 will be suliiciently energized to open the switch. Since this switch is included in the control circuit above described, it automatically permits thevalves 53, 54, 55 and 56 to close and to exhaust the air from thecylinders 48, 49, 50 and 51. T he switches 5 to 8, inclusive, are thus opened.

Variations in size and arrangement of parts and the circuit connections of the control systems may be eliected within the spirit and scope of my invention, and I desire that only such limitations shall be imposed as are indicated in the appendel claims.

I claim as my invention:

1. The combination with an electric motor, of a controlling switch therefor having a coil which tends to close it but is adapted, when normally energized, to hold it open, and means dependent upon the operation of the controlled motor for so opposing the action of the coil as to permit the switch to close.

2. The combination with an electric motor, of a controlling switch therefor having a coil which tends to close it but is adapted, when normally energized, to hold it open, and means dependent upon the counter-electro motive force of the controlled motor arma ture for so opposing the action or" the coil as to permit the switch to close.

3. T he combination with an electric motor, of a controller therefor comprising voltagereducing means, a plurality of governing switches having coils that tend to close them but adapted, when normally energized, to hold them open, and means dependent upon the acceleration of the controlled motor for successively reducing the forces exerted by said coils, whereby said switches are closed in a predetermined sequence.

l. A controller for an electric motor comprising an accelerating resistance, a plural ity of governing switches having coils that tend to close them but adapted, when normally energized, to hold them open, and opposing coils that are adapted to successively oppose the first named coils and to permit the switches to close in a predetermined sequence.

5. A controller for an electric motor comprising a plurality of accelerating switches that are adapted to close in a predetermined sequence and are provided with coils that In testimony whereof, I have hereunto tend, when energized within predetermined subscribed my name this 31st day of July, limits, to close the switches but are adapted, 1912.

when normally energized, to hold them open THEODORE VARNEY. 5 and additional coils acting in opposition to Witnesses:

the first named coils to permit the switches F. D. HALLOOK,

to close in succession. B. B. Hmns.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C.

Images