US1648674A - Electromagnetic device - Google Patents

Description

E. R. CARICHOFF ELECTROMAGNETIC DEVICE Nov. 8, 1927.

Filed Dec. 18. 1922 y WU Patented Nov. 8, 1927.

narran ySTATES #Para-Na formica EUGENE n. CAEICHOEE, Ao'E scHENEoT-ADY, NEW YORKHASSIGPNOR ro GE'NEnaL'ELEc- TRICC'OMPANY, A CORPORATION oF NEW YORK.

4Emac'iRoizrAGNE'rIc DEVICE.

Application fafa nember rs, 19'2'2. vseiai'No."61275576,

My invention 'relatesto operating Velectrolnagnets and inparticular to operatin'gelectroniagnets for electric switches.

.Theinvention 'has aparticular 1apphca- 5 tion in electromagnetic switches which vare used iin systems of motor control in which :the control ofthe electric motor 1s in r spense'v to the generated or counter-'electromot'i've torce o'f the motor, although the 1n- 10 venti n is not necessarily limited to such use. 'ne vof the difficulties encountered in controlling an electric motor in response to the generated or counterelectrongotive force of the motor is that of compensating for 13 variations in Vsupply circuit potential. An-

other difliculty encountered arises from the fact that the heating of the coils "o'fertl'ie Velectroiniagi'ietic .motor controlling 'switches vcausesth'e operation o f the s itches to vary.

2U v(In ny'fo'i'mer 'Patent-"No, 867,476, dated Ocito'ber', 1907, I have disclosedand claimed b'TU'ail'Iy amoto'r control arrangementinvo'lvthe use of the counterfelectromotive 'force principle in which compensation is if made vfor variations in line potential and for the heating of the swi'tc'h coilsJ and in my Patent No. 1,3115754, dated Jnly'2'9, 1919, I have disclosed and claimed an improved arrangement which involves the use of elec- 3-1 tr'mfagnetic switches of the lock-out type which are designed to hold open when the current is high and to close and lbe magnetically held closed when the effect-ive m`agnetic flux of the switch structure has is." dropped to a predetermined value. The arrangement disclosed in my .said 'ljate'ntNo- 1,311,754, while entirely operative and prat-- tical` leaves something to he desired from the standpoint of manufacture of the switch, 4u because of the fact. that the magnetic flux set up Vby the coil which tends to Ahold the switchin the open'position is rnterhnlred v-'i'ththe magnetic flux of the -coil which tends to close' the switch. By reason 'of the 4.; fact-that the flux across the closing gap of the switch is the controlling influence -in the operation of the switch, variations in the closinv flux or variations in the hold-ing` open iin-X render the switch uncertain -in op- 50 eration and Valso render it difhcu-ltto adapta single switch to various applications.

The 'present invention has for one of its objects the improvement of the operating electromagnets `for Vthe electric switches dis- 5-3 closed in my Aaforesaid prior patents. An-

to =l1old theysaid niem'ber from wlth a siibstanti'ally constant difference in jother of .the objets of the invention-iside provide an improved 'electrojina vice in whic'lijt-wo ent magnetic fo'rces tending to actuate 'the ment or member `of the electromagnet 'and gnetilclld'- substantially i independ- "the other vforce acting in oppositioh thereto actuating, the value of the magnetic forces while ithe ratio of the voltages applied to 4the'separa-te windings of the electroinagntsvaries. 'l :nother object ofthe `in'ventif'in is to, provide an improved electromagnetic device in 'which the separate `magnetic A)forces varyatfdifferent rates when the voltages applied "to the windings of the elect'romagnets' va'ryat the same rate. ,l

In carrying :the invention into effect, -I provide an .operating electromagnetic device for an electricswitch 'which 'hasfs'u'bs'tantia'lly independent .'ele'ctronia'gnets which ltogether control Va single magne't'ioinovable lmember for operating "a switch member.

Each of the electromagnets has asnbstantlally independent Vmagnet-ic strncture,l`so that ya variation in 'the Hux set upfjby one 'of the magnets has'su'bstantiallyfno effect o n the magnetic flux of the other electromagnet. When used in a lsystem of motorcontrol lfor start-ing a 'motor in accordance with 'a compensated counterselectromotive force principle, the one electromagnet- ,may have' its winding connected across the supply circuit so as to provide a 'holdinopen force which opposes the actuating orce of the other clectromagne't which has its winding connected to he energized in accordance with the counterelectroni0tive force of the .|notor. The magnet-ic structures of the opposing and the actuating electromagnets are such that there are'two vseparate kma netic forces vset up with respect tothe switc i member which have -a substantially constant .difference in value while t-he voltages applied to the windings of the electromagnets vary in value by a substantially constant difference, and the magnetic forces vary at a different rate when the voltages applied to the windings vary at the same rate. A The arrangement is such that by reason of the electromagnets having substantially*independent electromagnetic circuits, t-he effect of the closing 0r actuating elcct-romagnet may be varied independently of the holding-open or op* Vare. set up, lone fonce magnetlc' movable ele- .heating o'f'the switch coils,

voltage drop -a .numberof different conditions.

The arrangement is such`that when the switch is used in controlling an electric motor in accordance with the compensated connter-electromotive force principle, if, the line voltage varies, it will have substantially no effect onA the 4foperationof the switch in so` far as'the proper .control of the electric motoris-fconcerned-. In other words, ,the switch 'inherently compensatesgfor changes of the supply circuit potential' and for the l so that within the operating range of voltages of the switclnth'e switch. ,will be `operated by the actuating electromagnet when the voltage applied to the actuatingelectromagnet bears a 'certain relation-.to thefvoltage applied to the opposing electromagnet. Thuis, if it is desired tha`t;the switch yshall closejwhen the line 'voltage' is 100, and thefmotorcounterelectron'iotive force 'is .90l volts, if theV line to'ff90, thc"switch ,will close when A the motor,icounter-electromotive force is 30 volts.4

Foia better understandinghof my invention, reference' is fhadto v*accompanying drawings wherein I have 'shownan embodiment of myfiiivention in concrete form for `purpose'sof illustiatiom'and in which Fig. 1 is a sideA v iewof anv electromagnetic switch "constructed in accordance with my invention', Fig. 2 isa plan view of the same; 3 is a lvery simplified motor control diagram employing the electromagnetic switch of the invention; Fig. 4 is a 'curve showing there.- lationbetween the'relative Ipull and the relative excitation of the windings of the switch electromagncts; and Fig. 5 is a similar curve sheet showing a part ofthe curves of Fig. 4

to an enlarged scale, for the purpose of showing more clearly the manner in which there is a substantial constant difference in value of the magnetic forces exerted by the clectromagnets upon the switch member while the ratio of the voltages applied to the windings of the electroinagnets varies, or while the voltages applied to the windings of the electromagnets vary in value by a substantially constant difference.

Referring to the drawings, the electromagnetic switch is provided with two substantially independent electromagnets and 11 which cooperate to control the singleniovable switch member 12. 'Ihe electromagnet 10 has a magnetic structure which is practically independent of the magnetic structureof the electr-@magnet 1l, and both g of these' electromagnets control the pivotaily mounted magnetic movable member or armature 13 to which the switch member 12 is attached. The armature 13 is biased to s nch position that the switch member 12 is normally fout:l of engagement wvith;the stationary contact 14, so that the switchis normally in the open position. The winding of the'ele'ctromagnet 11 isadapted'v to' be' enelectromagnet 10 is adaptedto f be energized.

responsively to the co unter-electromotive Vforce of the motor, and whenifthefswitch is used in controlling thestaijting'p'f an'elcctric motor,l 'thehlower end of the armature 13 will'be attracted -bythe electromagnetll to hold the switch in theopen'position until the counter-electromotive force generated by the motor armature hashinc'reased to'fsuch a value that 'the `pull of 'the' electromagnet 10, which Ais provided Vwitlifa greater n um ber 4of turnsI of the,windirlig'l the, lwinding 11', ovc'rcomes 'the pull ofthe 'e1 tromagnet 11 and therebyfc'auses'theswitch ttfo'closc at the proper interval inthe ac'celeration'of the motor.

The Various parts of the electromagnetic switch are mountedupon the insula'tingbase '28, and the electromagnet 11 has a stationary core 15 with' whicli:the adjustablearmature 1G carried by the lowerend lof Lthe'armature 13 adapted to 4I riakeengagement@ The electromagnet `10 has a'magneti'cstructure comprising 'the core'l'?, the strap 18-and the magnetic member 19f which serves as astop for thearmature 13 -infcooperationfwith the 'strap 18. The armature 13 ispivotallyisup- Aported from the strap18. Thelines ofA flux set up bythe electromagnet 11 will substantially independent of theline'sfof :flux sc t up .by the electromagnet 1Q, so thatA the pull of each electromagnet. is not influenced by variations of magnetic iiurV in the other electromagnet due to the interlinking of magnetic fluxes as in the electromagnetic switch of my Patent No. 1,311,754. 'I he armature 16 may be adjusted with respectto the core 15 so as to vary the air gap between the core 17 and the upper. end ofthe armature 13 when theswitch is in the open position, thereby varying the value of the counter-electromotive force of themotor at which the switch will be operated to close.'4 i

The'operation of my invention will be understood from a descriptionof the opera'- tion of the motor control arrangement shown very diagrammatically 'in Fig. 3. In .order to start the electric'motor having an armature A and field F, the pilot switch 20will be closed to' energize the lline contactor 21 and thereby connect the motorto the source of supply 22 with the starting resistors El, It2 and R3 included in the motor armature circuit. The closing of the pilot switch 2O fiiil connects the windings 113, 11bfand 11c in series with the winding of the contacter 21 across the-supply circuit, and the lower ends 'of l'the -arma-t-ures 13a, 13b and 13 are attracted to movethei-r respect-ive Vswitch ineinbers farther away fronrthe closed position. '.lhe'fclosiiig of l'the 'line contactor 21 also en# ergi'ze's'thewindings ofthe closing electro'- inagnets 10?, 10b and 10c in seriesI relation across vt-h'ed-i'fiotor arn'iature Aso as to be energized, iesponsively to the counter-'electromotivev `force Aof the l"motor These windings will have a greater number of turns than the windings of the holding-open electromagnets, so that when the. conliter-electromotive force of the motor has increased to a predetermined value due to the speeding up of the motor, the pull of the electromagnet 10l will predominate over the pull of the electroft magnet 11a and the switch will close to short circuit the resistor R1. The resistors R2 and will be successively short circuited by their respective switches respoiisively to the speeding up of the motor in :i manner which will be well understood by those skilled in the art from the previous description.

The electromagnetic accelerating switches may be independently adjusted by adjusting their armatures 1G, 16" and 16c with respect to the armatures 13, 13b and 13 respectively,

so that the resistor R1 will be short circuited at one value of the counter-electromotive force, the resistor R2 at a higher value of counter-electromotive force, and the resistor R3 at a still higher value of counter-electroinotive force of the motor.

If the line volt-age varies above or below normal, the closing of the accelerating switches will be correspondingly effected. For instance, if the volt-age should be below normal, the fluxr due to the winding 11 will he a corresponding value less than normal, and the flux due. to the winding ltl will also be a correspondingly smaller value, so that when the voltage is lowered the switch will close at a lower Value. ot counterelectromotive force, and if the voltage is above normal the switch will close at a. correspondingly higher value of counter-electron'iotive force. Thus, by reference to Fig. 5, it will be seen that the magnetic circuits of the electromagnets are such that there will be a substantially constant difference in the separate magnetic fluxes set up by the two electromagnets while the applied voltages simultaneously vary. The magnetic forces thus vary at a different rate while the exciting currents in the coils vary at the same rate. The switch ,will therefore always close within the operatbeing the lnormal line voltage, 'if the line voltage drop to 90 'volts,ft`he switch -will close when the courr'ter-eleetromotive force 'is 8O volts, or ifthe'line voltage lris'estto 110 volt-s, 'the switch will close when the couIiter-electromotii'e fforce is' '1500'vofltsl The 'ratios of 10() to 90', 90 "to I8() aiid 110to`100are' all differentfbifit lth switchinheretly Atakes care otthis conditionyl' i' u Charities dterperatur li'ai'e"substantial iy fno emna-aespaaticn if aiefswieii 'because of the factthatsii'ice b'thco'i'ls are heated or cooled at substantially the same rate, the change in the pull of one electr0- magnet will be offset by the change in the pull of the other electromagnet. In other words, the switch will close at Substantially the same value of counter-eleetromotii-e force whether the winding 10 is cold or hot, since the winding 11 will be in a similar coiidition.

By reason of the fact that the calibration of the switch may be very readily changed by simply adjusting the armature 16 in position to thereby vary the air gap for the upper end of the armature 13 with respect to the core 17, the switch can readily be adapted to meet a great number of various applications. Furthermore, the ratio of the ampere turns of the windings 10 and 11 may be changed as desired in order to adapt the switch to various applications, and no account need be taken of' the fact that the inagnetic flux set up by one electromagnet is interlinked with the magnetic flux set up by the other electromagnet. Where it is necessary to take into account the interlinking of the magnetic fluxes of the two electromagnets, it is difficult to readily design a switch to give certain desired operating characteristics. In my present invention, by reason ot the fact that the magnetic fluxes` fet up by the two electromagnets are sub` stant-ially independent of each other, the elfect of each electromagnet on the switch member can be independently determined if desired without relation to the effect of the other eleetromagnet on the switch nien'iber. ln other words, the switch can be readily designed by calculation and a few simple experiments rather than by a cut and try method.

It will be observed that the switch is positively held open by an independent electromagnet which is directly energized from the supply circuit, thereby insuring that the switch will always be in the open position at starting and be held o-pen positively until the counter-electroniotive force of the motor increases.

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

A motor controlling electromagnetic device. comprising a magnetic movable meniber normally in one position, an electrolilo IUS

magnethaving .almagnetic structure and a winding thereon v for operating the said mem- .her toa second' position, a second electromagnet having a magnetic structure and a Winding thereon for holding the said member -in lthe first position against the pull of the first e1ectromagnet, the vsaid second electromagnet having a path for the magnetic linx which is substantially independent of the magnetic flux set up by the iirst electromagnet yand thel said windings and magnetic structuresl o lf the .electromagnets being proportioned `Ito set4 up twqiseparate magnetic forces which are exerted on said member and which have a substantially-constant differencein value while thelvoltages applied to the `windings of the electromagnets vary in valuel by a substantially constant difference andwhich vary atva differentiate while the voltagesapplied to said windings vary at lthe same rate. l l

In Witness whereof, I have hereunto set my hand this v1 5 th. day `of-December, 1922.

EUGENE R. CARICHOFF.

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