US1553069A - Electromagnetic device - Google Patents

Description

Sept. 8, 1925.

M. cRMER ELECTROMAGNETIC DEVICE 2 Sheets-Sheet 1 Filed March 23, 1922 InVenCov I Michel Cre'mef,

His bitter-n61) Patented Sept. 8, 1925. i

UNITED STATES?" PATENT OFFICE.

MICHEL CREMER, OF PARIS, FRANCE, ASSIGNOR 'lO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELEOTROIEAGNE'I'IC DEVICE.

Application filed March 23, 1922.

To all whom it may concern."

Be it known that I, Mionnn Gunmen, a citizen of Russia, residing at Paris, France, have invented certain new and'usetul Iniprovements in Electromagnetic Devices, oi which the following is a specification.

The electromagnetic device of the pres.

ent invention has a particular application as a relay for controlling the automatic starting of an electric motor by means of separately actuated electromagnetic switches or contactors, and although not nece sa rily limited thereto is particularly applicable to the starting of asynchronous motors having a wound rotor. These contactors are controlled by the electromagnetic relay hereinafter described. The purpose of this relay as employed in the control or" an electric motor is to produce automatically the progressive energization of a number of contactors in a predetermined order, the energization of the cont actors proceeding the decreasing starting current reaches a certain minimum value or in accordance with the acceleration of the motor. Thus the starting operation is always produced at normal torque and the acceleration depends upon the load on the motor.

In the case of induction motors with wound rotor, it is not practical to start by means of contactors without controlling-relays it being assumed that the potential and the frequency of the rotor circuit are v2.- riable. The only practical means consists in the use of acceleration relays, butin the starting systems generally in use, two are generally used, one of which controls the even contactors and the other the odd ones; from this arises a serious complication of the automatic starting outfits, especially when the number of steps is small, since it is necessary, for example, to have two relays to control three contac-tors.

The system, the description of which is given below, effects the starting as a "function of the intensity of an asynchronous motor, controlling any number of contactors through a single and relatively simple relay, the construction of which is based on the following principle:

Instead of two relays, a single one is employed having two different contacts which are closed alternately. One of these con tacts supplies the attracting coils of the Serial No. 546,1 19.

even contactors, and the other produces the release of the odd contactors. A series coil which is traversed by the principal current of the stator serves as a minimum-intensity coil; another fine-wire coil, connected to the potential of one phase serves to hold the movable part of the preceding coil and to commute the control-current by connecting it either to the first or to the second group of contactors. Due to this principle, the order of release of the contactors cannot be changed, that is to say, contactor No. 1, for example, cannot be closed before the closure of contactor No. 3.

The characteristic features and the advantages of the invention will be better understood by referring to the following description and drawings:

Fig. 1 represents a sectional elevation of the acceleration relay; Fig. 2 is a diagram of the connections of the relay in the case which applies to the automatic starting of an asynchronous motor with a wound rotor in four steps by means of a controller; Fig. 3 is also a diagram of connections, but modified with a view to a starting equipment for a low-power motor.

Referring to Fig. 1, the relay is composed of two separate magnetic circuits. The magnetic circuit 1 is excited by the series coil 2 traversed by the principal current of one phase of the controlled motor stator. This magnetic circuit is closed by the armature 3 which is pivotally mounted at i, or by the armature 5 situated behind 33 and which turns about the shaft. 6. The regulable springs 7 and 8 tend to release the two armatures. The second magnetic circuit 9, in the form of a U, carries a shunt coil 10, supplied by the voltage of one phase of the source of supply. Its reciprocating plunger core 11 carries at the top a guide rod12 of brass, with a regulable stop 13 and, at the bottom, another stop 14. hen the coil 10 is supplied with current, the core 11 rises, and since the stop 1st causes the amature 5 to rotate, the latter is brought to a stop, closing the magnetic circuit 1. On the contrary, when the attracting circuit of the coil 10 is broken, the upper stop 13 causes the arresting of the armature 3. The armatures carry two vertical blades with contact fingers 15 and 16, which establish respectively, at the stationary contact 17, the

will;

release circuit of the even cont actors, and at the stationary contact 18, that of the odd contaetors.

The operation of the relay will now be described, first in case 01" starting and then in case of stopping.

The diagram of connections oil the acceleration relay may be made in CGv'QlRl LlliliClfent ways. Fig. 2 represents one of the pos sible solutions; it is provided for the automatic starting of an asynchronous motor with wound rotor in four steps, by means of a control-switch. Assuming this diagram, the operation is as follows:

The. line switch 20 being closed, the contactor 21 is energized to close and thereby energize the stator 38 of the motor by closing the control-switch 19. This causes the establishing of the control-circuit through the fuse 25, the auxiliary contact 33 on the contactor 2 1-, the shunt coil 10 oil the relay and a protecting resistance Bel. At the same time, the motor starts, all the starting resistance being interpolated in the circuit oi? the rotor 39. The arn'iature ll of the shunt coil 10 is then attracted, releasing the armature 3, because the stop 13-3 lifted; but 3 cannot rotate, notwithstanding the tension of the spring 7, because the starting current produces a strong attraction through the series coil 2 and prevents the release ot the armature 3. At the same time the armature 5 is arrested by the stop 14. ll hen the intensity ot the current which is passing through the coil 2 has returned to its mini mum regulating value, in consequence oi? the acceleration of the motor, the armature 8 may be released, urged by the spring 7; it rotates, closingthe contacts lf'i li and causing the contactor to close. The at tracting coil of the contactor 22 is supplied with current through the auxiliary contact 26. hen the contactor 22 closes the coil 10 of the relay is short circuit-ed through the auxiliary cont ct 30 of cont-actor 23, auxiliary contact 27 ott'contactor and auxiliary contact 33 of contactor 24: The core 11 consequently falls, and holds by its stop 13, the armature At the same time the contactor 22 short-circuits the connections of the first section oi resistances.

The armature 5, which is then released by the stop 14:, does not rotate until the current through the winding 2 has sufficiently diminished; after this it rotates to the right and closes, through the contacts 16 and 18, the engaging-circuit of the contactor 23, which has been prepared by the auxiliary contact 28 oi? the preceding contactor 22. The contactor 23 then closes and short circuits the next rotor resistor by closing the connections 36.

The auxiliary contact 30 or the contactor 23 is opened by the closing of the conta :tor 23 and breaks the short-circuit around the coil 10, which is consequently re-excited and its core 11 rises and holds the armature 5 in the attracted position. The relay armature 8 is at the same time released; but it continues to be magnetically held in its positiou, due to the third point of current intensity which is produced in consequence oi the closing oi the contactor ll hcn the motor current again drops, the armature -3 is released and it closes, through the contacts l517, the circuit ol attraction oi? the contactor 24 which has been prepared by the closing of the auxiliary contact 31 of the contactor 23.

The contactor 2st, on making engagement, shmt-circuits, through the ctmnections 3?, the entire starting resistance. ii maintaiir ing circuit for the contactor Liis established tl'irough the contact 32 and the circuit oil the coil 10 is interrupted at the auxiliary contact 33; the relay is then returned to its original position.

For stopping, the control-switch 19 is opened, which operation causes the release oi the contactor 21 of the stator. The latter interrupts the circuit of the stator and the control-circuit of all the other contactors.

The regulation of the relay is produced independently for each armature, by means of the springs T and 8. Their tension regulated in such manner that the rel ase oil the armatures is effected at a certain minimum starting current, thus causing the starting of the motor as a function of the Value oi the motor current. Ii the motor starts at no load, its acceleration is ell'ected mode rapidly, since the points of intensity diminish rapidly; when the motor is loaded the starting operation is effected less rapidly, especially when the motor has to accelerate a large body.

In the preceding diagram each of the contactors 22 and has three supplementary contacts, which is not at all a disadvantage when the contactors are relatively large; but it the starting outlit is provided for a motor of low power and small cont actors, it is necessary to reduce the number of these contacts per contactor, in order to simplify the construction. Fig. 3 repre" sents the simplified diagram of control con-- nections which makes it possible to get an automatic starting operation by means of four contactors with the reduced number o'l siuiiplementary contactors.

The engagement of the contactor :2 l (stator) is effected by the closure of the switch 19. The control current passes through the fuse the auz-ailiary contact 24 of the contactor 2th. and it excites the shunt coil 10 of the acceleration relay which is mounted in series with the protective resistance 3d. The core 11 (see Fig. '1.) attracted; the armature 5 consequently stopped; the armature- 3 remains attractor by the coil 2 because of the current talren by the motor on the first starting point. When this starting current diminishes, the armature 3 closes the contacts 15-17, which causes the energization of the contactor 22. Its auxiliary contact 22 short-circuits the coil 10 and furnishes at the same time the holding current for the contactor, while its second auxiliary contact 22 prepares the engagement circuit of the contactor 23. The shunt coil 10 being short-circuited, its core falls, releasing the armature of the relay which, after a certain period of lag, is re leased and which produces, through the closure of the contacts 161S, the engage-- ment of the contactor 23. The latter is provided with two auxiliary contacts. The twodirections-contact 23 interrupts to the right; consequently it interrupts the hold ing circuit of the contactor 22, which is released; it thus breaks the short-circuit of the coil and closes, to the left, the holding circuit of the cont-actor 23. The contact 28 prepares for the closure of the contactor 2%. The coil 10, which is then re-excited, attracts its core, which releases the armature 3 of the relay. The latter, when the starting current due to the closing of the contactor 23 has been decreased, energizes by the closure of the contacts 17, the last contactor 24, the auxiliary contact 24% of which interrupts the control circuit passing through the coil 10 and the preceding contactors 22 and 23. The auxiliary contact 2& furnishes the holding current for the attracting coil of the contactor 24. The motor is stopped in the same way as before, by opening the switch 19. This arrangement requires, for each rotor contactor, only two suppleinentary contacts, which fact simplifies the auto matic starting of motors of low power by means of small contactors.

It will be seen that the invention has a particular application in systems in which at least three accelerating resistors and their corresponding contaotors are provided, the system being particularly applicable to systems of control having three or more accelerating contactors.

In accordance with the provisions of the patent statutes of the United States, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be can ried out by other means.

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

1. An electromagnetic device comprising a series electromagnet and two alternately operating switch members, each of which is movable from one position to a second position under the control thereof, and a shunt electromagnet having a magnetic movable element which moves the said switch members alternately to their first respective positions to be under the control of the series electromagnet and releases the switch members alternately to move to their respective second positions under the control of said series electromagnet.

2. An electromagnetic device comprising a series electromagnet and two alternately operated switch members, each of which is movable from one position to a second posi-' tion under the control thereof, and an alter nately energized shunt electromagnet having a reciprocating magnetic element which is connected to the switch member to alternately operate one of the switch members and to hold the same in its respective first position and release the other switch member to move to its respective second position under the control of the series electro1nagnet.

A relay for controlling electric motors comprising a series electromagnet, a plurality of magnetic movable members biased to the unattracted position controlled thereby, a pair of switch contacts controlled by each of said members, and a shunt electromagnet for alternately holding one of the said pair of contacts at a time in the open position.

4. A relay for controlling electric motors con'iprising a series electroinagnet, a plurality of nagnetic movable members biased to the unattracted position controlled thereby, a pair of switch contacts biased to the closed position controlled by each of said members, and a shunt electroinagnet having a mag netic movable member for alternately holding one at a time of said pairs of contacts in the open position and its associated magnetic movable member of the series electromagnet in the attracted position.

5. An electromagnetic relay comprising a series electromagnet and two pivotally mounted switch members biased to their respective closed positions and movable to their respective closed positions under the control of the series electromagnet, and a shunt electromagnet having a reciprocating plunger, the ends of which cooperate with the switch members for alternately moving one switch member to and holding the same in the open position to be under the influence of the series electromagnet and releas-' ing the other switch member to move to the closed position in accordance with its bias under the control of the series electromagnet.

In witness whereof, I have hereunto set my hand March 7, 1922.

MICHEL CREMER.

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