US1282017A - Motor-control system. - Google Patents

Description

G. E. STACK.

I010! CONTROL SYSTEM.

Armcmol min Jun :4. ma.

1,282,017. mm on. 15, 1918. 1"1 r" l f I; I

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' Geor e E.St.ack,

His ALL orn e5.

UNITED STATES PATENT OFFICE.

iE OBGE E. STACK, OF SCHENEC'IADY, NEW YORK ASSIGNOB TO GENERAL- ELECTRIC COMPANY, A CORPORATION OF NEW YORK.-

MOTOR-CONTROL SYSTELL.

Application fled July 24, 1918. Serial No. 246,434.

To all whom it-mag concern:

Be it known thatI, GEORGE E. STACK, a citizen of the United States, residing at- Schenectady, in the county of Schenectady,

State of New York, have invented certaln new and useful Improvements in Motor-Control Systems, of which the following is a. specification.

My invention relates to the control of electric motors and has for its object the provision of means whereby an electric motor may be started, stopped and .generally controlled. in-a reliable, simple and etficient manner.

My invention relates more specifically to the type of motor control involving the use of electromagnetic switches or contactors of the lock-out type. This contactor, as is well known, has the characteristic of holding its switch member 1111013611 position when the energizing current is above a predetermined value and moving it to closed position when the current drops to said value. Ordinarily in control systems ofthis character, the windings of the contactors carry the motor current so that when the motor circuit is. closed the winding of the series contactor is energized or if there is more than one contactor then the winding ofthe first contactor to close is energized by the motor current and the succeeding contactors are successively energized in a manner well understood. The result is that there is only one running position which is that in which all of the contactors are operated to cut out their resistance. In certain classes of work it is desirable to have at least two running positions, one of which may be the position with all of the resistance in circuit and the other with all of the resistance out of circuit. One of the objects of my invention is to provide means whereby this may be accomplished by utilizing the lock-out type of contactor without the use of a relay or other contactor.

In carrying out my invention I provide means whereby a lock-out contactor is connected between points of different potential of a starting resistance so that while the contactor winding does not carry the motor current it carries current which is proportional'to the motor current and. therefore,

hasthe same effect as if it carried the whole current. In one specificembodimentpf my invention I employ a controller which, in

its initial position, energizes contactors, preferably of the shunt type, for closing the motor circuit throu h the starting resistance. If, therefore, t e controller is left tively small so that it may readily be controlled at the controller contacts. When this first. contactor closes it short circuits aportion of the resistance, and if there are other contactors. they will successively op-. crate to cut out the resistance.

Other objects and purposes of my invention will appear in the course of the following specification in. which I have shown my Patented Oct. 15, 1918'.

invention embodiedjn a concrete form for purposes of illustration.

In the accompanying drawing, Figure 1 is a diagrammatic representation of one embodiment of my invention and in Fig. 2 is adiagram showing only the motor circuits.

Referring to the drawings, A represents the armature. F the commutating field and F the-series field of an electric motor to be controlled. C represents a controller which I have shown as of the reversing type having two forward positions f and f and two reversing positlons 1' and 1". This controller controls the reversing contactors 10 and 11 for forward running and 12 and 13 for running in the reverse direction. R, R? and R represent sections of resistances which are successively short circuited by electromagnetic switches or contactors 14, 15 and 16. These electromagnetic switches are of the well known lock-out type described .in the application of William J. Murphy, 'Serial No. 608,652 filed February 15. 1911, and assigned to the same assignee as this application. As is well understood,

the windings of these contactors ordinarily carry the motor current and when the cur rent is high the switch member is held in open position until the current falls to a when the current again decreases to the field F, contactor 10, armature A, commuproper value whereupon the switches are closed and are held closed by the windin By referring to Fig. 1, it will be noted that the contactor 16 does not carry the motor current nor will it be energized while the controller is in its first position f. This contactor 16 is energized on the controller contacts when the controller is moved to the second position f. It will further be noted that the winding is energized by being connected across a portion of the resistance. In the arrangement shown, it is connected across the resistance R so that it is subject to the drop across this resistance. The winding of this contactor is, therefore, a relatively fine winding and the current carried is only a fraction of the motor current so that it may easily be carried by the controller.

The mode of operation is as follows:

Assuming that the controller C is moved to the first position 7", the contactors 10 and 11 will be closed from line through the contactors of the controller to ground. The closing of these contactors closes the motor circuit from line through resistance R. R R successively thence through the will close and the same operation will occur.

It will thus be seen that I have provided a control system employing only lock-out contactors for cutting out the resistance in which itis possible to ope ate the motor with all the resistance in circuit in-onc position and in the next position have all of the resistance cut out.

While I have described my invention as embodied in concrete form and operating in provisions of the patent statutes, it will be understood that I do not limit my invention thereto, since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

hat I claim as new and desire to secure by Letters Patent of the United States, is

1. The combination with an electric motor, of means for controlling the same comprising a starting resistance, a nor mally open electromagnetic switch for controlling the resistance .which holds open when the energizing current is relatively high and .closes when the current decreases to a lower value and connections whereby the energizing winding of said switch is connected between points of different potential of said resistance to cause it to close as the current through the resistance decreases.

9. The combination with an electric motor and a source of supply of means for tating field F and contactor 11 to ground. If the controller is left in this position, the motor will run with all of the resistance in circuit. If now the controller is moved to the second position f, a circuit will be established from line through the controller C to contact 17 thence through the winding of contactor 16 to a point between resistance sections R and R The winding of contactor 16 is now subjected to the drop across the resistance R and will, therefore, close when thecurrent in the resistance decreases due to the speeding up of the motor. When this contactor closes the section of resistance R will be short circuited so that the circuit will now be from line through resistance R, through 'contacts of contactor 16, through the winding of contactor 15, resistance R and thence through the motorand. the shunt contactors back to the other side of the line. The winding of the contactor 15 carries the full motor current and resistance, means including a controller for connecting the motor to the source of supply through the resistance in its initial movement, a normally open electromagnetic switch for controlling the resistance which holds open when the energizing current is relatively high and closes when the current .decreases to a lower value and connections whereby upon further movementof the controller the energizing winding of the switch is connectedibetween points of'different po tential of said resistance to cause it to close as the currentthrough the resistance decreases.

3. The combination 7 with an electric motor, of means for controlling the same comprising a starting resistance, a plurality of electromagnetic switches for controlling the resistance which hold open when the enproper value due to the speeding up of the motor it will close thereby short circuiting resistance section R and energizing the winding of contactor 14. In like manner, the contactor 14 will close when the current. I reaches the proper value and a final circuit-1;: rgizing current is relatively high and will be established in the line through 'tlie close when the current decreases to a lower 'w nding and contacts of the contactor 14' value, and connections whereby the enerthence through the motor and line switches" gizing winding of one switch is connected to" the other side of the line. All. of the rebetween points of differential potential of sistance sections are thus short circuited said resistance to cause it to close when the and contactors 15 and 16 caused to open. current through the resistance decreases and In like mannerif the controller is moved to the reverse position contact'ors 12 and 13 the motor circuit.

a specific manner in accordance with the.

controlling the motor comprising a starting I connect the winding of another switch in 4. The combination with an electric motor and a source of supply, of means for supply throughthe resistance in its initial movement, a plurality of normally open electromagnetic switches for controlling the resistance which hold open when the energizing current is relatively high and close when the current decreases to a lower value.

and connections whereby upon further movement o t' the controller the energizing windingot one "switchis connected between points of different potential of said resistance to cause it to close when the current through the resistance decreases and connect the winding of another switch in the motor circuit.

In witness whereof, I have hereunto set 20 day of July, 1918.

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