US2477120A - Control device for starting windings of split-phase induction motors - Google Patents

Description

July 26, 1949. H. w. ECKER CONTROL DEVICE FOR STARTING WINDINGS OF SPLIT-PHASE INDUCTION MOTORS Filed NOV. 5, 1947 2O LAG LEAD FIG. 4

INV-ENTOR HOWARD w ECKER ATTORNZS I I I2 Patented July 26,. 1949 UNITED CONTROL DEVICE FOR STARTING WIND- INGS OF SPLIT-PHASE INDUCTION MOTORS Howard W. Ecker, St. Paul, Minn.

Application November 5, 1947, Serial No. 784,158

Claims.

My invention relates to control devices for starting windings of split phase induction motors and has for an object to provide a device operable independently of centrifugal force.

Another object of the invention resides in providing a control device which may be positioned remotely from the motor, permitting the motor to be encased within a sealed compartment.

A still further object of the invention resides in providing a device operable by virtue of the change in phase angle between the currents in the running. winding and starting winding of a split phase motor.

Another object of the invention resides in providing a core structure having three legs preferably arranged in the form of an E and including an armature pivoted about an axis disposed in proximity to the center leg and having two branches one adapted to be attracted by the pole on one outer leg and another branch adapted to be attracted by the pole on the other outer leg, one of said branches moving toward the pole of the corresponding leg and the other moving from the pole of its corresponding leg and vice versa as the armature swings about its pivot.

An object of the invention resides in providing a winding on the center leg adapted to be energized by the current in the running winding of the motor and producing magnetic flux through two paths, one including one of the outer legs and the other including the other of the outer legs,

Another object of the invention resides in providing a winding on the first named outer leg producing flux opposing the flux in said leg produced by the first named winding.

A feature of the invention resides in providing a switch operated by the armature and adapted to be opened when the armature is attracted by the third leg, said switch serving ,to de-energize the starting winding.

Other objects of the invention reside in the novel combination and arrangement of part-s and in the details of construction hereinafter illustrated and/or described.

In the drawings:

Fig. 1 is an elevational part sectional view of a control device for starting windings of split phase motors illustrating an embodiment of my invention.

Fig. 2 is a plan view of the structure shown in Fig. 1.

Fig. 3 is a plan section view taken on line 3-3 of Fig. 1.

Fig. 4 is a wiring diagram showing the use of my invention with a split phase motor.

Fig. 5 is a diagrammatic curve illustrating the relation between the currents in the starting and running windings of a split phase motor.

My improved control device consists of a core structure In which includes three legs II, I2 and I3, mounted on a, yoke or connection portion I4. This core structure is so arranged that the same is substantially E-shaped in form with the two legs II and I3 outermost, and the leg l2 at the center between the same. The legs II and I3 are formed with ends I5 and I6 which serve as poles for the said legs of the core structure.

The leg l2 of the core structure ID has an extension II which extends through a bracket or support I8 and which is riveted over to hold the said bracket securely attached to the hold. Agroove I9 extends across the said bracket and forms two corners 2I and 22 which serve as fulcrums for an armature 23. This armature has two branches 24 and 25 which extend over and are adapted to be attracted by the poles I5 and I6. Two screws 26 extend through the armature 23 and are threaded into the bracket l8. Coil springs 21 encircle these bolts and are seated at their lower ends against the armature 23 and at their other ends against nuts 28 screwed upon said screws. The two branches 24 and 25 of the armature 23 form a slight angle with one another so that the connecting portion 29 of said armature is slightly rounded and rests upon the support or bracket [8 merely at the two corners forming the fulcrums 2| and 22. Springs 21 engaging the armature 23 hold the portion 29 of said armature in engagement with the said f-ulcrums as clearly shown in Fig. 1. The armature is so designed that when in such position the air gap 3| between the branch 24 and pole I5 is very slight while the air gap 32 between the pole I6 and branch 25 is considerably greater. Shins 30 on the armature 23 prevent the same from sticking to the poles I5 and I6.

Mounted on the leg I2 of core I0 is a winding 33 which is adapted to be energized by the current in the running winding of the motor with which the device is to be used. On the leg II is a similar winding 34 adapted to be energized by the current in the starting winding of the motor. It will be readily comprehended that the winding 33 produces magnetic flux in the leg I2 which passes through two paths, one including the leg I l, air gap 3| and branch 24 of armature 23, and the other which includes the leg I3, air gap 32 and the branch 25 of armature 23.

The leg I3 at the locality of the pole I6 is formed with a transverse slot 62. .In this slot is disposed a ring of copper or some other nonferrous conducting material which encircles a portion 63 of said pole and serves as a shading coil for causing positive attraction of the armature 23 by said pole when the branch 25 is brought into proximity thereto.

Formed on the bracket I8 is an arm "35. This arm hasattached to it a bar 36 "of insulating material which is provided with a contact 31 forming one element of a switch 38. The end of the branch 25 of armature 2'3 ihasattached to it a bar 39 of insulating material which again is provided with a contact 4| forming the other element of said switch. The contact 31 is mounted on a threaded stem 42 which is-screwedinto the insulating bar 36. This contactirnay be adjusted with reference to the contact 4| by means of an adjusting nut 43 screwed on said "stem, A second nut 44 on saidistem serves to attach a conductortothe con tact. A similar flexible-nonduct-or, not enown, is attached "to the :contact 4-! ibyfsoidering or iotherwise.

Eoi' th'e pur-pose o'f illustrating the invention, .'I have snown diagrammatically in Fig. 14, a :certain split phaseapaoitor induction motor 45. This motor has a roto'r '46, :a run'ning winding #41, a staming wirrdin'g-am ianda capacitor- 48. The two windings lia -arid 1:83am connected together and to a common conductor fifl which'inturniis connetted to one side bf a lineiswitch 5 5. The other end of the winding 48 is connected :by means :of a conductor :55 to the capa'citor 4'9. Theendsi-of the two windings-Stand are :connected Ito etheriand to a conductor 5.2 which in lturnis connected toithe iother side pfithes switch 51. The switch ti I tisfifurth'er connected to :a source 10f salternating current whichlhas' -b'een iiiagrammaticalliyiiniiiliated Fasla line153. The other side of thetrunning: winding 4? :is connected by :means of a conductor =54to the other :endof the winding 33. The oth'er send of the winding :34 'is connected rhyzmieans .of a conductor :55 to the movable militant- H Onarma'tureQ-ZB. 'Theefixed contactial-tof this rswitchris connected ibyrme'ans ofxarconductor sfi tocthercapacitor 3'9 fOfltheZIIlO- tor 45.

*In Eig. J5, .ZIJhave :shown :a curve illustrating the nel'ationrlietween the phase .anglefiofxthe scurrents iizpassing through 51116 starting wizidingand the lrlinning'avindingiofathe marticular: :motor 745. Theicui ve 58 :is the icurve s' fror the startin fwin'dingandztheicurvefiais the-'icurve forithecunning winding. It' will i be f noted that i the epha-se :angle for tithe star-ting windingiiseleadingsatlow speeds and th'ait' the' phaseiangle for Ethe lrunning winding is lagging at low speeds. -It :will-ibeiurther noted fithat t'he qahase angle .of the currents :in the :two windings becom'e's substantially equal when the t wo cur ves cross which is at substantrall'yvsfl o'f synchronous 'speed for this :particularm'rotor.

The theory-10f operationdf the invention is as follows: The armature 23 is 'normally in the pcsition shown in l i'gj l with the air gap 3 small,

and therair gap 32 largeia'ndzwith the switch sfi' open. At themoment the switch 51 is closed, the?r-unningiwindingllis energized. Thisca'u'ses flux to fiOW fih1011g h bOth the iegs i i and 3 of core" Ill. :Airzg'ap L31 being- 6flesserlength'than air gap :32, t;he branch M- of "armature -iii is attract'ed to mom t? and l the switch :38 'c'lose's.

During isu'oh movem'er it theaarmature zrocks on ifil'crum :24 ol'osure of -theswitch 38-=energizes these fluxes isisubstantiail and the saidzfluxes add vectorially to 'p'roduce' a resultant flux having greater attractive force on the branch 24 of armature 23 than the attractive force exerted on branch :25 of saidrarmature by the portion of the ;produced by winding 33 and passing through the leg I;3-.'?and:air gap 32. As the motor picks up speed thedifference in phase angle between the 'two "windings becomes less and less until theifiu-Xes ifromithezsaid windings become substantially in phase which occurs when the speed of the motor is substantially of synchronous speed. At such time, the attraction of the pole ifior: thezatmaturesbranch :24 substantially ceases' simzeitheitwoafluxesiproduced loy the windings 3 ands34 in ithea leg I I -=substantially. cancel out. At 'hthis time .the lflux ifrom winding 33 through ithe :leg r13 iissufiicient to :cause the pole tl3a1to= attract the ranch z5iof zarmaturesz3and to swing the .said rarmature xpole L5. This opens :SWfiTGh 3538 enuineenergizes ithe startingzwinding :48. thefiiux produced by windin 33 is snow reflective. -However, ithe airgap 3:2 nasan'ow becomeasmall and thezairgap 31 has increased rso that ithe branch 25 Of ;the arms.- ture is held attracted to the palle -2H5 awit'h only normal noiload icnrrent flowing in ithe winding 33. :In :the imovement r'oi the armature to isu'ch positionlthe samerrocksgmithe'iulcmm u. Upon opening *OfilthBiSWitChfi'I minding-M: ibe'comes de- Themarts areithuszresetmndiathe i-motorvi-suready to be. stantedsagain. ln the i event ithat the :mo-

tor;:s.p.eed is :reduced ito 3168s Ethan =80% speed switchs38 wviill not beiClUSfidIIliilfiSSi th -m0t0r is de-zenergized, Eithlls :preven'tin renergiza-tion of the starting winding :and mossiblelburning outof the :same.

While'I' have shownithe switch 38 as :normally open it wean ozeadily comprehended that f th'e contact 33;! rmayrehetadijusted 'itoizcanse the-same to be .::normally :closed. :In.:such 0356, :Ilynamic br akingrof theam'otoraresultsrandrthezrotorzof the motor is quickly brought to rest.

The advantages eof invention .are r-manitest. By means of ;my :invention the starting winding control deviceqcanzbe i-placed exteriorly of the motor, thus gpetcmittingeofrthe;=inserti-on:of the :motor .within.a; sealed/case and: eliminating the .ruseeof pressuresseals. My.=-improved: lde-izi-ce isJindependent of time [and will (not operate to deeenergize the sstarting iwvinding-l-until the; motor gets up to its desired speed. .il hefideyicecan be-. constructed .at zaerelativelyaeconomical scost. Due to -the.'fact..that .there .-.is .a considerable edifference "in .phaseiang'le'between .;the-. currents.- in the starting and running windings at-lowspeeds my device becomes positive ineaction and .will reduce failure to cstarttola .minimum. v=The.-device will operate satisfactorily .on wide variation "iniine voltage. LContacts33 .cambe se'tshormally'closed andthus accomplish dynamicbraking when capacitor type motors are used. The

device *in' the 'form'shown will not reconnect'the.

tacts are readily accessible for cleaning and replacement whenever the occasion requires it.

Changes in the specific'form of my invention, as herein described, may be made within the scope of what is claimed without departing from the spirit of my invention.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:

1. A relay for use with a split phase induction motor having a running winding and a starting winding and in which the phase angle between the currents in the running winding and starting winding is greatest at low speeds and approaches zero at a, higher speed, said relay comprising a magnetic core structure, having three legs provided with poles, an armature pivoted for swinging about an axis disposed in proximity to the pole of one of said legs and movable toward the pole of another leg and from the pole of the third leg and vice versa, a switch operable by said armature and moved into operative position upon movement of the armature toward the pole of said second leg, a winding on said first leg adapted to be energized by the current in said running winding, a winding on said second leg adapted to be energized by the current in said starting winding, said windings being connected to procure operation of said switch when the phase angle between the currents in said running and starting windings approaches zero to cause said switch to de-energize said running winding,

2. A relay for use with a split phase induction motor having a running winding and a starting winding and in which the phase angle between the currents in the running winding and starting winding is greatest at low speeds and approaches zero at a higher speed, said relay comprising a magnetic core structure, E-shaped in form and having three legs provided with poles, an armature pivoted ior swinging movement about an axis disposed in proximity to the pole of the center leg, said armature having a branch movable toward the pole of one of the outer legs and another branch movable from the pole of the other outer leg and vice versa, a winding on said center leg adapted to be energized by the current in said running winding, a winding on the first named outer leg adapted to be energized by the current in the starting winding and producing a flux opposing the fiuX produced in said leg produced by said first named winding, and a switch adapted to be connected to the starting winding and having a part movable with the branch of said armature acting with the third leg of said core structure, said branch upon movement toward said third le opening said switch and when attracted by said third leg holding said switch open until de-energization of the winding on the center leg.

3. A relay for use with a split phase induction motor having a runnin winding and a starting winding and in which the phase angle between the currents in the running winding and starting winding is greatest at low speeds and approaches zero at a higher speed, said relay comprising a magnetic core structure, E-shaped in form and having three legs provided with poles, an armature pivoted for swinging movement about an axis disposed in proximity to the pole of the center leg, said armature having a branch movable toward the pole of one of the outer legs and another branch movable from the pole of the other outer leg and vice versa, a winding on said center leg adapted to be energized by the current in said running winding, a winding on the first named outer leg adapted to be energized by the current in the starting winding and producing a flux opposing the flux in said leg produced by said first named winding, and a switch adapted to be connected to the starting winding and having a part movable with the branch of said armature acting with the third leg of said core structure, said branch upon moving toward said third leg opening said switch, and resilient means for normally holding said switch in open position and said branches spaced from said poles, the distance of said first named branch of said armature from its pole bein less than the distance of said second named branch of said armature from its pole.

4. A relay for use with a split phase induction motor having a running winding and a starting winding and in which the phase angle between the currents in the running winding and starting winding is greatest at low speeds and approaches zero at a higher speed, said relay comprising a magnetic core structure, E-shaped in form and having three legs provided with poles, an armature pivoted for swinging movement about an axis disposed in proximity to the pole of the center leg, said armature having a branch movable toward the pole of one of the outer legs and another branch movable from the pole of the other outer leg and vice versa, a winding on said center leg adapted to be energized by the current in the running winding and producing magnetic flux passing through two paths, one of said paths including the first named outer leg and the other including the second named outer leg, a winding on the first named outer leg adapted to be energized by the current in the starting winding and producing flux in said le opposing the flux produced in said leg by the center leg winding, said fluxes cancelling one another as the phase angle between the currents in said winding approaches zero and releasing said armature for movement toward the second outer leg to open said switch.

5. A relay for use with a split phase induction motor having a running winding and a starting winding and in which the phase angle between the currents in the running winding and starting winding is greatest at low speeds and approaches zero at a higher speed, said relay comprising a magnetic core structure, E-shaped in form and having three legs provided with poles, a winding on the center leg adapted to be energized by the current in said running winding, a winding on one of said outer legs adapted to be energized by the current in the starting winding and producing a flux opposing the flux in said leg produced by said first named winding, an armature extending across said poles and having branches adapted to be attracted by the outermost poles, two spaced parallel fulcrums for said armature disposed at the locality of the center pole and supporting said armature with the branch adjacent said first named outer pole spaced from but close to said pole and the other branch spaced from and remote from the other outer pole, resilient means for holding said armature against both of said fulcrums and a switch carried by said armature and adapted to be connected to the starting winding circuit and open when the armature is in normal position, said switch being adapted to be closed by said armature when said first named branch of the armature is attracted by said first named outer pole and remaining open when the second named branch is attracted by the second named outer pole.

HOWARD W. ECKER.

(References on following page) 1mm.) "rn o w ng r. uqes 1 9 lewd i :m

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:8 Name Date .;Pearce N0v. 1:9, 1935 S chaefer Mar. 18, .1-941 FQREIGN PATENTS Country Date ma e. M YZ 11

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