US1079480A - Motor-control system. - Google Patents

Description

J. EATON.

MOTOR CONTROL SYSTEM.

APPLICATION FILED 00127. 1912.

1,079,480. Patented Nov. 25, 1913.

Fig. l,.

2 2% 3: L 7 u a 22 [36 25*:

r C ,27 D J 2 2/- 2.9' a ,R

/2 L I L 34 & a

Witnesses Invehtor-z JOhnE on, fl%'% Pmmumw WAsnluuruN. n. cy

UNITED STATES PATENT OFFICE.

JOHN EATON, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

MOTOIR'GONTROL SYSTEM.

Application filed October 7, 1812.

Specification of Letters Patent.

To all whom it may concern:

' Be it known that I, JOHN EATON, a sulr ject ofthe King of Great Britain, residing at Schenectady, in the county of Schenec= tady,' State of New York, have invented certain new and useful Improvements in Motor-Control S stems,- of which the following is a speci cation,

This invention relates. to the control of electric motors and has for its object the provision of means whereby an electric inotor may ice-started, stopped and reversed in a' reliable, simple and efiicient manner.

My invention relates more specifically to the control of reversible electric motors, one of the objects of my invention being to provide improve-d means whereby an electric motor may be brought to rest by dynamic braking of the motor armature and then started in the opposite direction of rotation;

In carrying out my invention I' employ two electromagnetically operated switch members, one for causing the motor to be operated in each direction. These two switch members normally engage two correspondingcontacts connected with one side ofthe supply circuit and when their actuating-windings are energized are moved into engagement with contacts connected with the opposite side of the supply circuit. The arrangement is such that when the switch members are in their normal position the brake resistance isnconnected in a short circuit with themotor armature so as to quickly bring the latter to rest. To this end a braking resistance is connected in series with the motor armature bet-ween the switch members, the resistance being preferably connected so that it will notbe in circuit when the switch member to which it is connected is in its actuated position but is in circuit when it is in its normal position. I

View of one form of my invention: and Fig.

2 represents a slightly modified form.

Referring first to Fig. l, A represents the armature and F the shunt field of the motor to be controlled. Two elect-romagnetically operated switches C and D are providech'one for operating the motor in each direction. These two switches cooperate espectively with two contacts 10 and 11 connected to the positive side of the line and with contacts 12 and 13 connected with'the negative side of the line. These switches are provided with movable switch members 14: and 15, respec tively, so that in one position they engage the contacts on one side of the line and in the opposite position engage the contacts on the opposite side of the line. These switch members are normally in engagement with the contacts 12 and 13 that is, they are given a bias to this position. The movable switch member 1 1 is provided with contacts 16 and 17 for engaging the contacts 10 and 12 respectively, while the switch member 15 is 19 for engaging the contacts 11 and 13 respectively. The contacts of the switch member are electrically connected as shown and the motor armature A is connected between these sets of contacts. WViththis arrangement when the two switch members are in normal position so that the switch contact 19 engages the contact 13 and the switch contact 17 engages the contact 12 the motor armature will be short circuited on itself. In order to bring the motor to rest quickly when the contacts are in the position shown I provide the brake resistance R which is adapted to be connected in the braking circuit when the switches are in normal position. In the arrangement shown in the drawing this resistance R is connected between the motor armature A and the contact 19 of the switch member 15. In order to hold the switch contacts firmly in their normal position during the dynamic braking of the motor I provide two windings 20 and 21 one for each switch. The winding 20 is connected between the contact .12 and the negative side of the line while the winding 21 is connected between the contact 13 and the negative side of the line. The switch members 14 and 15 are electromagnetically operated by the actuating windmgs 22 and 23 espectively. The switch 24 is arranged to provided with corresponding contacts 18 and connect either the winding 22 or the winding 23 with the positive side of the line. The winding 22 connected with the negative side of the line through the contacts 13 and 19 of the switch D, while the winding 23 is connected to the negative side of the line through the contacts 12 and 1.7 of the switch C. With this arrangement it is necessary that one switch be in its normal or denergizing position before the other switch can be operated. The specific structure of the switches C and D form no part of my present invention but for purposes of illustration I have shown them in the form of what is commonly known as the double throw contactor. The two switches are identical in construction and each consists of two angular magnetic forms 25 and 26 insulated from each other as shown in the drawing, the two cores 2? and 28 of the windings 20 and 22 respectively cooperating with these frames to form in effect a U-shaped magnetic frame. The two switch contacts 16 and 17 are connected by the link 29 so that the contacts move together. An operating arm 31 pivoted at 30 to the magnetic frame 26 and pivot-ed to the link 29 cooperates with the core of the winding 22 to raise the link 29 and move the switch contact 16 into engagement with the contact 10. When the arm 22 is deenergized the link 29 drops in response to gravity in the position shown in the drawing. The contact 17 has an extension forming an armature 32 cooperating with the core 27 of the winding 20 so that when the latter winding is energized the switch contact 17 will be pulled into firm engagement with the contact 12.

As thus constructed and arranged the operation of my device will be as follows. If the switch 24 is -moved into engagement with Contact 33, thecircuit will be from the positive side of the line, through switch 2 1, winding 23, conductor 34, contacts 17 and 12, winding ,20 to the negative side of the line. tuated and bring the contacts 18 and 11 into engagementso as to close an armature circuit from the positiveside of the line through contacts 11 and 18, conductor 35, armature A, contacts 17 and 12, winding 20, to the negative side of the line. The windin 20=beingenergized, the armature circuit is firmly c osed at the contacts 12 and 17. In likemanner, when the switch 24 is moved into engagement with the contact 36 the switch will be moved to open position and the actuating winding 22 of the switch C will be energized from the positire side of the line, through winding 22, conductor resistance ll, contacts 19 and 13, winding 21 to the negative side of the line. This will complete the circuit tl'irough the armature in the opposite direction from the positive s de of the line, through the contacts 10 and 16,

This will cause the switch 1) to be acconductor 34, armature A, resistance R, conlacts 19, 13, winding 21, to the negative side of the line. When, however, he switch 24.- is between the two contacts 32 and 36 and not in engagement. with either, both switches C and D will be. in the normal position shown in the drawing and a dynamic braking circuit will be closed through the armature A, conductor brake resistance R, contacts 19, 1", winding 21, thence to the winding 20, contacts 12,17, and conductor 3 1 to the other side of the armature. It will be noted that the two windings 20 and 21 are included in this dynamic braking circuit so that the circuit is firmly closed at the switch contacts. It will thus be seen that by a very simple arrangement the m0- tor is alwaysdynamically braked when the switch is in the oil position and will be operated in either one direction or the other as the switch is ,mo'ved in opposite directions, it being impossible for both switches C and D to be actuated simultaneously. Furthermore, with this arrangement of circuits it.- is impossible for the switch to close for one direction of rotation of the motor armature. while the latter is rotating in the opposite direction. It will be observed that the'wmdings and 23 each has a. terminal connect-- cd with a terminal of the armati'n-e .r. The connections are such that when the motor armature is rotating in one direction its counter eleclromotive force is opposed to the clectromotivc force impressed on the winding which causes the armature to rotate in the opposite direction. For instance, when the switch 24- is in engagement with contact 3 and the winding 22.; is energized to close the switch i), the circuit will be from the positive side of the line, through the wire 35, armature A, contact 12, and winding 20 to the negative side of the line. \Vhen now the switch 24- is moved on to contact 3G and the circuit of the wire 35 is opened at the contact 1.1, the counterelectromotive force of the armature will be in the direction opposing the electromotive force impressed upon the winding 22. This winding 22 can, therefore, not be energized sutficientlyto operate the switch C'until the motor armature stops. The same is true with the winding 23. This taken in connection with the fact that the actuating winding of each switch can only be energized when the opposite switch in the open position makes it. absolutely certain that the reversing switches must operate in their proper order.

It will be noted in connection with Fig. 1 that the braking resistance R is in circuit during one direction-of rotation of the motor that is, when the switch C is closed. In some cases this might not be desirable, but in certain cases, as for instance on a printing press where the press is backed up at slow speed this resistance would he an advantage. Tn some cases, however, it is desirable that the resistance It be eliminated from the circuit while the motor is running in both directions. Under these circumstances I have provided the arrangement shown in Fig. 2. This arrangement is not different from the arrangement shown .in Fig. 1 in any particular except that the resistance R is short circuitcd when the electromagnet C, corresponding to the switch C of Fig. 1, is closed. This is accomplished by providing a pivoted switch member 37, which is closed noon the fixed contact 38 when the switch C is actuated, the switch 38 being connected with one terminal of the resistance by the conductor 39 while the cow tact 37 is connected with the opposite terminal resistance by the conductor 40. With this arrangement it will be seen that when the switch C closes the armature circuit instead of passing through the resistance R passes through the switch contacts 38 and 37.- During the dynamic braking operation, however, the resistance R is in circuit as before.

W'hile I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the patent statutes, it should be understood that I do not limit my invention thereto since various modifications thereof will sug gest 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.

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

1. The combination with an electric motor and a supply circuit therefor, of means for reversing the motor comprising a pair of contacts connected to one side of the supply circuit, a corresponding pair of contacts connected to the opposite side of the supply circuit, two electromagnetically operated switch members connected with the armature terminals normally engaging the contacts on the same side of the supply circuit and movable into engagement with corresponding contacts on the opposite side of the supply circuit, a resistance connected between one armature terminal and one switch contact so as to be in series with the armature only when said switch contact is in its normal position, and a switch arranged to ener ize the actuating electromagnet of either 0 said switch members.

2. The combination with an electric motor and a sup ly circuit therefor, of means for reversing t e motor comprising two contact members connected to one side of the supply circuit, switch members having contacts normally engaging said contact members, a resistance connected in series with the motor armature between said switch contacts, and an electromagnet for disengaging either of said switch members from its corresponding contact member and connecting it to the opposite side of the supply circuit, each magnet being energized through the contact of the switch operated by the other magnet in its normal position.

3. The combination with an electric motor, of means for reversing the same comprising two electromagnetic switches one for each direction of rotation of the motor, and connections whereby the counter electromotire force of the motor when caused to rota'te in one direction by the actuation of one of said switches o poses the energization of the actuating win ing which causes the motor to rotate in the opposite direction.

4. The combination with an electric motor and a supply circuit therefor, of means for reversing the motor comprising a pair of contact members connected to one side of the supply circuit, a corresponding pair of contacts connected to the o posite side of said circuit, two switch mem ers connected with the armature terminals movable into engagement with one of each pair of said contacts and normally engaging the contacts on the same side of the supply circuit, and a resistance connected between one armature terminal and one switch contact so as to be in series with the armature only when said switch member is in its normal position.

5. The combination with an electric motor and a supply circuit therefor, of means for reversing the motor comprising two contact members connected to one side of said circuit, switch members having contacts normally engaging said contact members, a brake resistance connected in series with the motor armature between said switch contacts so as to be in a closed circuit with the motor armature when the contacts are in normal position, and a winding connected in the braking circuit for holding each switch member in its normal position.

6. The combination with an electric motor and a supply circuit therefor, of means for reversing the motor comprising two contact members connected to one side of the supply circuit, switchmembers having contacts normally engaging said contact members, a brake resistance connected'in series with the motor armature between said switch contacts so as to be in a closed circuit with the motor armature when the contacts are in normal position, a winding connected in the braking circuit for holding each switch member in its normal position, and an electromagnet for disengaging either of said switch members from its corresponding contact member and connecting it to the opposite side of the supply circuit, each magnet being energized through a contact on the switch operated by the other magnet in its normal position.

7. The combination with an electric motor and a supply circuit therefor, of means for reversing the motor comprising two contact members connected to one side of said circuit, switch members having contacts normally engaging said contact members, a brake resistance connected in series with the motor armature between said switch contacts so as to be in a closed circuit with the motor armature when the contacts are-in normal position, and means for short circuiting said resistance when the motor armature iscorinected across the supply circuit 8. The combination with an electric motor and a supply circuit therefor, of means for reversing the motor comprisin a pair of contacts connected to one side '0? the supplycircuit, a corresponding pair of contacts connected to the opposite side of said supply circuit, two switch members connected with the armature terminals movable into engagement with one of each pair of said switch contacts and normally engaging-the contacts on the same side of the supply circuit, a resistance connected between one armature terminal and one switch contact the other switch member for short circuiting said resistance when said member is moved out of its normal position.

9. The combination with an electric motor and a supply circuit therefor, of means for reversing the motor comprising a pair of switch contacts and normally engaging the contacts on the same side of the supply circuit, a brake resistance connected between one armature terminal on one switch contact so as to be in a short circuit with the motor armature when said switch members are in normal position, a winding connected I in the braking circuit for holding each switeh' member in its normal position, an

electromagnet for disengaging either of said switch members from its corresponding contact and connecting it to the opposite side of the supply circuit, each magnet being energized through the contact on the switch operated by the other magnet in its normal position, and means for short circuiting sa d resistance when the motor armature is connected across the supply-circuit.

In witness whereof, I have hereunto set my hand this day of October, 1912.

JOHN EATON.

\Vitnesses BENJAMIN B. HULL, HELEN Onronn.

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

as Washington, D. C. I

Images