US1720613A - Time-element device and motor-control system employing the same - Google Patents

Description

y 9, 1929- G. B. STARIE 1.720.613

TIME ELEMENT DEVICE AND MOTOR CONTROL SYSTEM EMPLOYING THE SAME Original Filed May 4, 1925 Fig. I.

. George B. fitarie, D65 I Hmrneg.

Patented an 9, 1929.

U -lTED STATES PATET orric GEORGE E. STABIE, OF BOHENECTADY, NEW YORK, ASSIGNOB 1'0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

'I'IEE-ELEHENT DEVICE AND MOTOR-CONTROL SYQTEE EMPLOYEE THE .1;

Application filed Kay 4, 1925, Serial K0. 28,038. Renewed January 24, 18%.

My invention relates to an improved electro-responsive time element device for general purposes, and in particular to an electromagnetic time element device for controlling the 5 operation of motor controlling switch alter the operation of another motor controlling switch.

My invention also relates to an improvedmotor control system employing the'im roved time element device of the invention or obtaining the desired succession of operation of motor controlling switches or contactors with a desired time interval interposed between the operation of successively operated contactors.

The present application is directed to improvements of and is covered b a copending application of Eu ene R. Caric iofi and Benjamin W. Jones, erial No. 527,520, filed Jan.

6, 1922, a renewal of an application, Serial No. 354,030, filed Jan. 26, 1920. I

Time element control of electromagnetic switches, as heretofore proposed, has left something to be desired in the way of a simplc, reliable and effective device which invariably gives the desired time interval of operation. Motor control systems operating on the time element principle, as heretofore proposed, have also left something to be desired in that complications are introduced which render the system uncertain in opera- .tion.

' In carrying my invention into efiect, I employ an electromagnetic time element device of very simple construction, and one which when employed in a motor control system, for example, makespossible a very simple, efiective and reliable s tern for producing the intended control 0 the motor. The electromagnetic time element switch is provided with a magnetic structure with a winding thereon and a magnetic movable element armature carrying a switch contact, the armature being biased to the unattracted position and the switch contact carried by the armature being biased to a definite position, as for example, the closed position. 'The armature of the electromagnetic time element device is biased to the unattracted position by any suitable means such as a spring, the tension of which may be adjusted so that when the arms-- ture is in the attracted position, it is ma netically held inthat sition against t e action of the spring tending to move the armature to the unattracted position. The winding of the electromagnet is connected so as to be shunted when a previously operated switch is closed. By reason-of the fact that the winding has a considerable inductive efiect, the short-circuitmg of the winding will perhill; the induced current to maintain a magnctic flux in the magnetic structure of the electromagnet and thus maintain the armature in the attracted position for an appreciable interval of time. The winding is provided with a suthcient number of turns so that with the armature in the attracted position, the ma etic flux of the relay will be considerably in excess of that required to hold the armature in the attracted position thus insuring that the time interval introduced will not be appreciably affected by such variables as variations of the supply circuit potential or variations of the heating of the winding. Adjustment of the time elementis obtained by adjusting the air gap between the armature and the core of the electromagnet, and this is preferably done by mounting a shim of non-magnetic material on the armature so that when the armature is magneticall operated to the attracted position, the slum will insure that there will be a definite and invariable air ga between the armature and the pole face. he time interval may be very accurately ad'ustcd to the desired value by employing a im'of the correct thickness for the particular time interval desired. The time interval is also adjusted by varying the tension of the spring which biases the armature to the unattracted position, since the time interval is obtained by the pull of the induced flux of the electromag'net overpowering the strain of the spring tendin to move the armature to the unattracted position. The ad'ustment obtained .by varying the strain 0 the sprin is (Luite accurate and is simpl obtaine so t at as a practical matter, a ter a suitable thickness of shim has been determined, the principal adjustment will be by var ing the spring tensionjgi; I

or a better understanding of the Invention, reference is had the accompanying drawin in which Fig. 1 1s a very simple dragram 0 a time element motor control system n accordance with the invention Fig. 2 is a side view of an electromagnetic time element relay in accordance with the invention, and Fi 3 is a front view of thesame. fieferri first to Figs. 2 and seen that t e time element switch or relay 3 it will be.

no j

comprises an electromagnet structure including the strap of magnetic material 10 and the core 11 of magnetic material on which the winding spool 12 is mounted. The strap 10 and the core 11 are secured in any suitable manner to an insulating supporting base, as for example, b means of the bolt 13. The magnetic mova le element or armature 14 of the device is pivotally mounted with respect to the strap 10 and is biased to the unattracted position by means of the spring 15. This spring is mounted on a bolt 16, which is carried by the support 17 secured to the strap 10.

The nut 18 is provided for adjusting the tension of the spring 15 and thus varying the time interval of operation of the device. The shim 19 of non-magnetic material is secured to the inner face of the armature 14 so as to make abutting engagement with the end of the pole face 11 when the armature is in the attracted position, thus introducing a definite and invariable air gap between the armature and the pole when the armature is in the attracted position.

The armature carries a contact 20 at its lower end thereof, and this contact is arranged to make engagement with the stationary and adjustable contact 21. The contact 21 is carried by means of a strap of electrical conducting material 22, which is secured to the insulating support by means of the bolt 23. The arrangement is such that a single winding on the electromagnetic device controls the entire operation thereof and this winding has a sufiicient number of turns so that with the armature in the attracted position the magnetic flux of the electromagnet is considerably in excess of that required to maintain the armature in the attracted position. When the winding 12 is short-circuited, the inductive efi'ect of the electromagnet is employed to maintain. the armature in the attracted position .for an appreciable interval of time, and

by reason of the fact that the holding flux was considerably in excess of that required to maintain the armature in the attracted position, this time interval will not be a preciably affected by the variables which a. cot previous time element devices, namely, variations of the supply circuit potential and variations of the heating of the winding.

In Fig. 1, the electric motor having an armature 24 and a series field winding 25 is arranged to be connected to the direct current supply circuit 26 by means of the pair of directional contactors 27 and 28 for the forward direction of motor operation and the pair of directional contactors 29 and 30 for the reverse direction of motor operation. The line contactor 31 is provided for opening the motor circuit upon failure of power and the connections are such that .the master controller 32 must be returned to the off or neutral position in order to reclose this contactor. The current taken by the motor is limited by means of resistance in the motor armature contactor 34 and the accelerating IGSIStOIS' 35 and 36 controlled by the accelerating contactors 37 and 38, respectively. The plugging contactor 34 is under the control of a plugging relay 39. This relay is intended primarily to delay the energization of the plugging contactor 34 upon a rapid reversal'of the motor by the well-known plugging action, aI 1 d the relay is provided with a winding 40 for determining the sequence of the closing of the plugging contactor 34 with reference to other parts of the system. The winding 41 is connected across the resistors 33 to 36 so as to give a current limit control for this relay.

The accelerating resistor contactor 37 is controlled by means of the time element relay 42, of the construction shown in more detail in Figs. 2 and 3. In general it may be said that this relay is provided for giving a time interval of operation after the closing of the plugging contactor 34, dependent practically entirely onthe inductive efiect of the relay when the winding of the relay is shunted in response to the shunting of the plugging resistor 33. s

As thus constructed and arranged, and with the parts in their respective positions indicated in Fig. 1, the operation of the system is as follows: The disconnecting switch 43 in the main motor circuits, and the disconnecting switch 44 in the control circuits will first be closed. The closing of the disconnecting switch 44 will cause the line contactor 31 to be energized to close, the circuit being from the positive supply conductor, segment 45 of the mastercontroller 32 and segment 46 of this controller, through the winding of contactor 31 to the negative supply conductor. The line contactor 31 in closing, will also close the auxiliary switch 47, thereby establishing a maintaining circuit for the line contactor and permitting the master controller to be moved out of the off position without affecting the energization of the line contactor.

It will also be observed that when the disconnecting switch 44 is closed, the winding of the relay 42 will be energized across the supply circuit with the resistor 48 in series with the relay winding, and that the winding 40 of the relay 39 will also be energized across the supply circuit with the resistor 49 in series with the relay windingJ These two relays will thereforebe energized to open their respective contacts, preparatory to later operating to produce the intended control of the motor. If now the master controller 32 is thrown to the full runningposition forward (the master controller thrown to the left final position), the directional contactors 27 and 28 will first be closed, thereby connecting the motor to the source of supply for forward direction of motor operation, the coils of contactors 27 and 28 being energized through the segments 46 and 50 of the mas ter controller. The directional contactor 27 will close its auxiliary contacts 51 and thus shunt the winding 40 of the relay 39 so as to place this relay under the control of the winding 41 which is now energized responsively to the voltage drop across the resistors 33 to 36 inclusive. The closing of the directional contactor 28 will simultaneously close the auxiliary switch contacts 52, thereby partially completing a circuit for the winding of the plugging contactor 34, the circuit being from the negative supply conductor, winding of contactor 34, segments 53 and 54 or the master controller 32, to the contacts of the relay 39, but since these contacts are temporarily at least maintained open, the closing of the auxiliary switch contacts 52 will not effect the energization of the plugging contactor 34. However, as soon as the motor current has dropped to the predetermined value, the winding 41 of relay 39 will be unable to hold the relay contacts in their open position against the strain of the spring 55 and this relay Will close, energizing the plugging contactor 34 to close through the circuit previously traced and the segments and 46 of the master controller and the auxiliary switch 47 to the positive supply conductor.

When the plugging contactor closes, it also closes its auxiliary switch contacts 56, thereby shunting the winding of relay 42. As previously explained, this relay is of the construction illustrated in more detail in Figs.

2 and 3. Although the relay winding has been shunted, the relay will not release its armature for an appreciable interval of time, due solely to the inductive effect of the relay winding. When the magnetic holding effect of the flux of the induced current is overpowered by the biasing spring of the relay, the relay will very quickl close its contacts, thereby energizin the winding of the resistor contactor 37 t rough a circuit from the negative suppl conductor, contacts of relay 42, winding 0 contactor 37, segment 57 of master switch 32, segment 54 of the'master switch, contacts of relay 39, auxiliary switch 52, segments 50 and 46 of the master switch auxiliary switch 47 to the positive sup ly conductor. Contactor 37 in closing also 0 oses its auxiliary contacts 58, thereby energizingthe resistor contactor 38 to close. The resistor 36 will ordinarily be of comparatively small value as compared to the resistors 35 'and 33 so that the time interval of operation of the closin of the contactor 38 after the contactor 37 wi be suflicient for certain applications.

thrown to the full reverse position, since those skilled in the art will readily under-.

from an understanding of the operation whenv full reversal is had.

When themaster controller moves out of its third operative forward position, the accelerating contactors 37 and 38 are directly deenergized and opened and when the master controller moves out of its second operative position forward, the plugging contactor 34 will be deenergized and opened. The introduction of the resistance in the motor armature circuit will cause the winding 41 oi the relay 39 to he again momentarily energized in accordance with the drop in potential across the resistors 33 to 36-, inclusive, and the opening of the auxiliary switch 56will remove the shunt about the winding of relay 42 so that relays 42 and 39 will both open. The relay 39 willhave a further opening effect applied thereto by the energization of the winding 40 in response to the opening of the auxiliary switch contacts 51 of directional contactor 27 when the master controller is moved out of its first operative forward position to the neutral position, It may be said at this time that while the above stated operation has been assumed to be taking place at a certain definite sequence, this has been done merely for the purpose of explanation of what could be the case but which is not necessarily in all cases the lexact sc uence, since if the master contro ler is t rown very quickly from the full forward position to the full reverse position, the opening of the resistor cont-actors, the directional contactors and the opening of the relays 42 and 39 will be almost simultaneous.

When the master controller reaches the first reverse position, the directional contactors 29 and 30 will be closed, and the Winding 40 of the relay 39 will be shunted through the auxiliary contacts 59 of the contactor 29. The relay 39 will not close its contacts until the current in the motor armature circuit has decreased to a redetermined value, at which time the windlng 41 is sufiiciently reduced in energization so that the relay may close. The closing of the plugging contactor 34 as a result of the closing of the relay 39 will effect the shunting of the winding of the relay 42 as before, and this relay will introduce the same time interval etween the operation of the plugging contactor 34and the acceleratin contactor 39, as was previouslythe case i or forward motor operation. The accelerating contactor 38 Wlll close promptly after the closing of the contactor 37 in the manner previously explained.

It will be observed that I have provided a ve simple and effective time element relay which de ends for its time of operation on the invariable time required for the holding effect of the fiuxof therelay when the winding of the relay is shunted. The operation of the relay contact from and to the closed position is entirely under the control of the flux set up by the winding of the relay. The-relay is of itself a very simple, effective and reliable ,device, and one which can be manufactured in large scale production for a materially lower cost than other time element devices with which I am familiar. The provision of the simple, effective and reliable adjusting devices of the relay afford means whereby the time interval may be very accurately adjusted to the exact time desired, and as before stated, this determined time interval will be invariable for all practical purposes. This electromagnetic time element relay is covered in a divisional application, Serial No. 125,112, filed J uly'26, 1926. It will also be observed that the control system in which I employ the time interval relay for obtaining the desired time interval of operation between the closing of the plugging contactor 34 and the accelerating contactor 37 is very simple, thus tending toward a great reliability of operation.

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

' 1. In combination, a motor controlling switch, a motor controlling resistor, a contactor for shunting the resistor, and a normally closed electromagnetic time element relay for controlling said contactor to control the shunting of the resistor a definite interval of time after the closing of said switch, the winding of said relay being connected to be shunted at the same time that the said switch is closed and the time element of operation of the relay being effected solely by the inductance of the relay.

2. In combination, two motor controlling contactors, an electromagnetic time elementrelay for delaying the energization of the second of said contactors for an interval of time after the closing of the first of said contactors, the said relay having a winding which is connected to be energized to open the relay quickly against its bias to the closed position when the first contactor is open and to be shunted when the first contactor closes, the operation of said relay to the closed position and the time interval introduced thereby to the closed position being determined solely by the inductance of the relay.

3. In combination, in a system of motor control, a pair of directional switches, a plugging resistor,-a contactor for, shunting said resistor, a single relay for controlling the in moving from the open.

closing of the pluggi n contactor the said relay having two win ings which cooperate to open the relay andhold the same in the.

open position, one of said windings being connected to be energized when said directional switches are open and to be shunted by the closing of either of said directional switches, and the other of said windings being connect-ed to regulate the closing of the relay in accordance with the motor current, a time interval after the shunting of said first winding.

4. In combination, in a system of motor control, a pair of directional switches, a plugging resistor and an accelerating resistor, a contactor for shunting each of said resistors, a single plugging relay for controlling the closing of the plugging contactor, the said relay having two windings, which cooperate to open and hold the relay in the open posi tion, one of: said windings bein connected to be energized when said directlonal switches are opened and to be shunted by the closing of either of said directional switches, the said other relay winding being connected to regulate the closing of the relay in accordance with the motor current an interval of time after the closing of either directional switch, and a single winding normally closed time element relay for controlling said accelerating contactor, the winding of said accelerating relay being connected to be energized to open said relay when said directional switches are open and to be shunted by the closing of said plugging contactor to delay the closing of the re- I lay andthe closing of the accelerating contactor for a definite interval of time after the closing of the plugging contactor.

5. In combination, two motor controlling switching mechanisms, the second switching solely by the inductance of said winding is introduced in the closing of the second switching mechanism in accordance with its bias. a

In witness whereof, I have hereunto set my hand this 2nd day of May, 1925.

GEORGE B. STARIE.

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