US1872128A - Elevator control system - Google Patents

Description

Aug W F EAMES ELEvAToR'coNTRoL SYSTEM Filed April 5, 1928 Fig. I.

INVENTOR Wil/iam FEames.

r A'TTORNEY Patented Aug. 16, 1932 UNITED gsrA'riez's PATENT OFFICE WiLLIAMr. EAMES, oF'wrIJxINsBURG, PENNSYLVANIA, AssreNon 'ro WnsTIN-snousn ELECTRIC' a MANUFACTURING COMPANY, A CORPORATION or PENNSYLVANIA `ELEVATOR CONTROL SYSTEM Application lved April 5,1928. Serial No. 267,711.

Anotherk object of my invention is to provide a control system for an elevator motor wherein the elevator may be stopped accurately level with the floor withoutoverrunning or underunning the floor.

Another object of my invention is to provide a control system for elevatorsof the lllard-Leonardv type wherein the ygenerator structure is modified toy insure accurate speed regulation of the motor atlow speeds independent of loading conditions,

`Another object of my invention is fto provide a system, as described in the preceding paragraph, wherein the commutatingpoles of a generator may be 'so `arranged as to achieve an effect of cumulatively compounding the generator at such timesy as tliegen-y '2s erator is operating at low voltages and low currents.

In elevator systems controlled by means of variable-'voltage equipment for use in modern installations, it is desirable that the elevator speed/shall be regulated within comparatively'narrow limits, independent ofthe load upon the elevator, since, in high-speedelevator work, the accuracy of landing is vator should be the same, regardless of the load thereon, when operating under predetermined conditionsy of control.

To accomplish this result, the Ward- Leonard or variable voltage systemof control has beeny devised wherein variations ink the speed of the motor which would` normally occur with. variations in the load upon to produce such rising voltage characteristic ou. the generator as will compensate for the the elevator are compensated kfor byy meansk of eumulatively compounding the generator" generator substantially accomplishes this result within rather wide ranges o load.

It has been observed, however, that a degree of generator compounding effective to provide satisfactory motor-speed regulation throughout the major portionof the load range,'is ineffective to provide satisfactory regulation between motor-load values of from zero' to a small percentage (usually approximately 10%) offull load. The observed variation in generator voltage has ybeen found to increase, in accordance with load, to a maximum of several volts at the suggested percentage of fullr load.

IV hen the elevator motor is operating at the slow speed required just prior to stopping at a floor, the voltage of the generator is correspondingly low, usually of the order` of from 10 to 20 volts. At these low voltages, a variation in Igenerator voltage of several volts is sufficient to cause a considerable percentage variation ink motor speed, and corresponding variations in the point at which an elevator may bebrought to rest.

In accordance with my invention, I propose to correct for the above noted discrepancies in generator Voltage by imposingv an adt ditionall degree of cumulative or differential compounding (depending upon the character of the load) on the generatorthroughout the suggested range of load values. As will be more fully described hereinafter, I effect this additional compounding of the generartorby providing an additional component of commutating pole flux.` yBy, properly desienin the magnetic circuit traversed b the commutating pole flux, I effect a cumulative compounding of the generator between the suggested positive load values and a differentialV compounding of the generator between the suggested negative load values,

whereas, forload yvalues throughout 'the remainder of the load range, the degree" of compounding imposed by the commutating poles remains at a substantially constant value. y

My invention will be described with reference to the accompanying drawing, wherein, @Figure l is diagrammatic viewrof an elevator-control system of the Ward-Leonard type. u

Fig. 2 is a diagrammatic view of the generator showing the arrangement of. main poles and commutating poles, a portion of which view is in section, and

Fig. 3 is a diagrammatic view of a voltage curve obtained by the usc ot the generator hereinafter described.

Referring to the drawing, I have illustrated, in Fig. 1, an elevator car C supported upon a suitable cable Ca which passes over a hoist drum D to a suitable counterweight C11'. The hoisting drum D is illustrated as directly coupled to the armature EM ot a hoisting motor EM, the field winding EMF et which is connected for excitation by a suitable source of energy designated by conductors L1 and L2. The armature EM of the motor EM is connected in loop circuit with the armature G of a generator` G. The generator is provided with a. separately excited lield winding GF a series iield winding GSF, a demagnetizing winding GAF, and a commutating pole winding GC. The generator G is driven by means of a suitable motor M, illustrated as of the shunt-wound type having its armature M and its shunt eld winding MF connected across line conductors L1 and L2.

The control of the direction and speed of the elevator car Ga is illustrated as of the usual type wherein up and down-direction switches 1 and 2, respectively, actuated by means of a car-switch C3, control the direction of current supplied to the separately excited field winding GF of the generator G, while a speed switch 3, controlled by the car switch C8, is arranged to control the value of the current supplied to the field winding GF.

Referring to Fig. 2, the generator G, the structure of which per se is claimed in my copending application, Serial No. 560,694, filed September 2, 1931 as a division hereof, and assigned to the Vestinghouse Electric and Manufacturing Company, is illustrated diagrammatically ot the four-pole type, wherein the main poles are designated by the reference characters 5, 6, 7 and 8, respectively. Suitably located between the main poles 5, 6,

etc., I have illustrated commutating or interV poles 9, 10, 11 and 12, it being understood that the number of inter poles corresponds to the number of main poles provided on the generator G. is is the usual practice in generators of this type, each of the inter poles is provided with a winding (one of which is designated by the character 13) suitably connected in series relation with each other and with the arma-ture G.

Each of the inter poles 9, 10, etc. may be provided with a core 14 suitably secured to the frame 15 of the generator G by means of a bolt 16. The core structure 14 and bolt 16,

as' well as the frame structure 15, are all constructed of suitable magnetizable material. Interposed between the core member 14 and the frame 15, is a shim or washer 17 constructed of non-magnetizable material, for example, copper, brass or fiber. As is well known, the interposition of a section of non-magnetizable material between the frame 15 and the core member 14 constitutes the equivalent of an air gap between these members. Hence, a portion of the magnetic path through the inter pole 9 is constituted with a relatively small cross sectional area o low reluctance and a relatively large section of high reluctance.

he operation of my system will best be understood from an assumed operation of the elevator car C. Assuming that it is desired to move the car C upwardly, the car switch C8 may be moved in a counter-clockwise direction to energize 11p-direction switch 1 by means of a circuit which extends from line conductor L1 through conductors 20 and 21, contact members 22, 23 and 24 on car switch CS, conductor 25, the coil of 11p-direction switch 1, conductors 26, 27, Contact members 37 of an inductor relay 37, and conductors 39 and 40 to line conductor L2. Up-direction switch 1, when actuated, supplies current in one direction to the generator-field winding GF by way of a circuit which extends from line conductor L1 through conductors 29, contact members a of 11p-direction switch 1, conductor 30, separately excited field winding GF, conductor 31, resistor 32,

conductors 33 and 34, contact members b of up-direction switch 1 and conductor 40 to line conductor L2. Generator G now supplies Voltage to the armature of elevator motor EM, and the car C starts upwardly. The voltage supplied by generator G will be dependent upon the value of exciting current in the separately-excited-tield winding GF with the addition of voltage induced by the cumulative-compounding elfect of the series-field winding GSF. The effect of the winding GSF, since it is in series relation with the armatures G and EM of the generator and motor, respectively, will be greater or less dependent upon the load on the elevator car C at any given instant. An additional degree of generator compounding, also determined by the load on the elevator, is imposed by the commutating poles, as will be described more in detail hereinafter, in connection with Fig. 3. Hence, regardless of the load upon the elevator car C, the motor EM will be supplied with sutlicient voltage to insure its operating at substantially constant speed for any given value of excitation current suppled to the separately-eXcited-field winding In the system described and illustrated, the control is of the ordinary inductor-landing type wherein slow down is automatically initiated and the car is brought to a stop, with- Cil kfio

out intervention on the part of the operator,

by means `of slow-down n inductors 35 and 36 for .the up yand down directions, respectively, and stopping inductor 37. f v

When the up-direction switch lis actuatedr to close its contact members a, a self-holding circuit is completed thereby for kmaintaining the up-direction switch l in its actuated position until stopping inductor Vrelay 37 opens its kcontact members 37 yThis holdingcircuit extends from a line conductor L1, through conductor 29, contact members a'of up-di` rection switch l, conductors 30fand 38, the coil of 11p-direction switch 1, 'conductors 26 and 27, normally-closed contact members .37 of stoppingv inductor relay 37, conductors 39 ,and 40 toy line conductor L2; Hence, `until l l stopping inductor relay 37 is actuated,the 11p-direction switch will remain operative and the car ywill continue its upward movement, even though the car switch C8 is centered.

H it is desired to move the car C at a greater speed, the car. switch Cs may be moved to the'left to its extreme position, supplying energizing current rto speed switch 3 by way. of a circuit which extends from line conductor Ll through conductors 2O and 21, contact members 22, 23 and 41 on car switch Cs, conductor 42, the coil of speed switch 3 and conductors 43 and 40-to lineconductor L2. The actuation of speed switch 3 shunts resistor 32 from the field-winding circuit by way of conductors 44 and 45, thus increasing the value ot excitation current supplied to the separately-excited-eld winding GF. Hence, the elevator motor EM will accelerate andoperate at Lthe speed corresponding to this newv value of field excitation.-

When speed switch 3 is actuated. it completes a self-holding circuit foritself, which circuit extends from a line conductor L1 through conductors 29 and 46, Contact members b of speed switch 3, conductor 47, contact y, members 35 of up slow-down inductor 35,

conductor 48, `contact members 36of slowdown inductor relav 36, conductors 49 andv 42. the coil speedswitch 3 and conductors 43 and 40 to line conductor L2.

When it is desired to stop the elevator car, the car switch Gs will be returned toits central or illustrated oli position. By reason of the .holding circuits for" up-direction r switch `1 and speed switch 3, previously described, the car will continue its upward motion at high speed.A Centering the car switch Cs, however,-closes acircuit for energizing the actuating coils of inductor relays 35 and 37. This circuit extends rfrom line conductor L1 throughconductors 20 and 21, cout- act members 22, 23 and 50 on car .switch` Y C8, conductor 51, the coil of stopping induc- Y tor relay 37 conductor 52, the coil offslowdown inductor krelay 35, conductor- 53, ycon'- tact members d on 11p-direction switch 1 and vecmductors 54,55 and 440 tov linesccmductor L2.

yinal topping of the car.

vided at each of the floors past whichthe elevator moves) and the inductor relay 35,

`now energized, is actuated to open its contact members 35.4 `Opening contact members 35 releases the holding circuit for speed switch 3, which switch .is restored to its normal condition, kopening its contact members a and reinserting resistor 32 in circuit with the separately excited field winding GF to reduce the speed of the car in correspondence with the value of excitation current now sup-v Vplied to field vvindingGF.

As the car approaches more closely to the desired floor, stop inductor relay 37 will be ,brought adjacent an Vinductor plate 37 `associated therewith (one of which also is located adjacenty each of the floors past which the car moves) and relay 37 will be caused lto open itscontact members 37 to release the holding circuit for up-direction switch 1. [lp-direction switch will, when deenergized, open the circuit for the partly excited eld winding GF, and the car will be brought to a stop. It will be observed that, with the system of control just described, the elevator car C will be decelerated from its normalv high speed to a landing speed prior to the For accuracy, in landing the car level, it will be apparent that thek speed of the car at this low landing speed should be constant for all loads placed f uponl the carribecause the distance from the floor at which slow down and stop are initiat ed is fixed by the relative positioning of the inductor plates 35" and 37". f

It will be observed that, under the condi-f tions just described, contact members c of updirection switch 1 will complete a circuit connecting the demagnetizing-ield Winding GAF across the terminals of the armature `EM of the elevator motor EM. The demag- "i assumed that, when the motor EM is brought to a stop, the usual mechanical brake (not shown) will be applied to maintain the car stationary.

Referring .to Fig. 3, to illustrate the influence of my invention on a generator, I have shown characteristic voltage curves of a cumulatively compounded generator suitable for elevator applications, in which generatorvoltage values are plotted as ordinates, against generatorload values, expressed in lli) lil() percentages ot' full-load current, as abscissae. The curves illustrate the variations in terminal voltage from a negative or overhauling load of approximately full load to full load. The no-load voltage is shown as approximately l5 volts, which, as hereinbefore stated, corresponds to a typical landing speed of an elevator motor. Curve 56 is typical of a generator provided with normal compoundine` means, while curve 57 illustrates the improved voltage regulation effected in the practise of my invention.

Referring to curve 56, it will be observed that, throughout the load range from 10% to full load in the positive direction, and from 10% full load to the extremity of the curve in the negative direction, the voltage ot the generator is very nearly proportional to-the load. Between the limits of a 10% positive load and 10% negative load, however, the slope of curve 56 is seen to depart from the substantially constant value noted with respect to the remainder of the load range.

For purposes et simplicity, I shall hereinafter refer to that portion of the load range throughout which the slope of the curve is substantially constant as the major portion of the load range, and to that portion ot the load range throughout which the slope of the curve departs from the desired or substantially constant value as the restricted porrgtion7 oi the load range.

since the slope of curve 56 throughout the restricted portion of the load range diii'ers from that throughout the major portion of the load ranffe, it will be apparent that a degree of compounding etiective to produce a desired landing speed7 of the elevator motor throughout the major portion ot' the load range, will be ineffective to produce the same motor speed throughout the restricted portion thereof. rrs noted hereinbefore, a small actual variation in generator voltage throughout the restricted portion of the load range, when the elevator' motor is operating at the landing speed, constitutes a considerable percentage variation.

Curve 57 represents a desirable voltage characteristic for a generator', in that the variations in generator voltage are substantially proportional to the generator load throughoutthe entire load range. By organizing a generator in accordance with my invention, the voltage characteristic thereof may be caused to take the form of curve 57.

By comparing curves 56 and 57, it will be seen that the slope of curve 56 may be corrected to conform to that of curve 57, by subjecting the generator' to an additional component ot' excitation, the value of which varies as a function of the generator load throughout the restricted portion of the load range, and remains substantially constant throughout the major portion thereof. The

manner inr which the described construction of the commutating poles of the generator is effective to produce this result may be set forth as follows.

To provide satisfactory commutating characteristics for the generator, the flux set up by the commutating pole windings should be substantially proportional to load throughout a predetermined range of load values, and should be of such a value as to substantially compensate, at the zone of commutation, for the flux set up by the current in 'the armature windings. If, now, the flux of the commutating pole windings is permitted to predominate, to a predetermined degree, over the flux set up by the current in the armature windings, the current in the commutated armature coils will be prematurely reduced to zero and reversed. The reverse current flowing in the commutated coils, of course, sets up a flux which is of such a direction as to add or subtract directly to or from the flux of the main field windings, and thus exerts a compounding action on the enerator. It ollows that this compounc ing action is cumulative when the load is positive, and diiferential when the load is negative, since the commutating pole windings carry the load current.

As described hereinbefore, this additional component of generator excitation should be proportional to load throughout the restricted portion of the load range, and should remain constant throughout the remainder' thereof. In other words, the rate of increase of commutating-pole flux should be greater throughout the restricted portion of the load range than throughout the remainder thereof.

Referring again to the construction of the commutating poles, it will be observed that the magnetic circuit for the flux of the windings thereot comprises a main pole core, a connecting bolt, and a non-magnetic spacer. When both the pole core and bolt are unsaturated, it is apparent that algiven increase in load current will produce a given increase in commutat-ing-pole flux. If, now, the bolt is permitted to saturate at a predetermined valueot1 load, it follows that subsequent increases in load will produce smaller increases in commutating-pole flux. In accordance with my invention, I permit the bolt to saturate at the point at which the slope of curve 5G assumes the desired value.

It will be seen, therefore, that, throughout the restricted portion of the load range,`the commutating pole flux increases as such a function of the load as to perform not only its normal function, but to supply an additional component of main generator excitation in proportion to the load; that, throughout the major portion of the load range, by reason of the saturated condition of a portion of its magnetic circuit, the flux of the com- Lemma mutating poles increases less rapidly, or, in creases as such a Jf'unction of the load thaty the additional component of generatorexcication supplied thereby remains substantially constant. In accordance with my invention, therefore, when the load is positive or negative, the generator voltage corresponding to a particular load is increased or decreased to such an extent as to cause the actual voltage characteristic of the generator to assume a,

that the arrangement just described achievesy an effect of correcting the inaccuracy ofspeed regulation to the extent of at least 50% and this amount of correction is readily appre- L ciated when the control system herein described is applied to elevators having a device or automatically stopping the elevator .car level with the floor, such as that herein described and also described in the copending application of E. M. Bouton, Serial No. 731,291, filed August 14, 1924, and assigned to the Westinghouse Electric and Manufacturing Company. With such automatic landing equipment, initiation of slow down at a definite distance lfrom the loo-r, regardless of the load on the elevator, causes the car to `stop substantially level with the floor without further attention on the part of the attendant. In actual test, such systems stop the car level with the floor Within a half inch, regardless of load. However, by the use of the system for providing additional compounding of the generator, as herein described, such inaccuracy can be reduced to less than one-fourth of an inch.

Another method of accomplishing the result of effecting an equivalent of advancing the commutating plane is illustrated in Fig. 2 wherein the core 14 of the commutating pole is spaced from the frame 15 by a pair of lugs 60, formed integrally with the pole core 14 or introduced as spacers. This construction provides an air gap 61, and the ole operates in the same manner as described for the core 14. In this case, however, the bolt 16 should be constructed of non-magnetizable material.

My invention may be practiced in many ways, the embodiments herein described are illustrative only, and I do 'not desirey to be limited to any of the details shown or described ytherein except insofar as deinedin the appended claims.

I claim as my invention: f e

1. In a motor-control system, a motor, a

generator .for supplying yvoltage to said m07.

tor, meansf'for variablyy excitingsaid generator4 to cause said ymotor to be operated at speedsy corresponding thereto and `means for cumulatlvely compounding saidy generator be` tween. restricted load limits, saidl compounding ymeans j including ay 'main-ieldpolesup rting frame` on said generator, comnmtat` ingpoles for said; generator, a gap between said.y frame and said poles formedof nonmagnetizable material and `rnagnetrizable meansv of less cross sectional area` than said" poles .for bridging said gap.r

2. In a motor-control system, ya motor. a generator for supplying voltage to said mo tor, means for variably exciting said gener# ator to .cause said motor to be. operated. at speeds corresponding thereto, and means for cumulatively compounding Asaid generator;V

between restricted load limits, said compounding means .comprising a main-fieldpole-supporting frame on said generator, commutating poles on said generator spaced from theirsupporting frame by non-magnetic gaps and magnetizable means of preingsaid gap. A

3.Inv a motor-control system, a motor, a generator for supplying `voltage to said motor, means for variably exciting said nic gaps andfbolts of vmagnetizable material of predetermined cross section for securing said poles tosaid frame. v

4. In a motor-control system, a motor, a' cumulatively-compound-wound generator for'supplying voltage tol said motor, means for variably exciting said generator to cause said motor to operate at speeds corresponding thereto, and additional means for cumulatively compounding said generator, between restricted load limits, said compounding means including a lmain-pole-ield-supporting frame on said generator, commutating oles for said generator spaced from said rame by gaps composed of non-magnetizable material, and magnetizable means of less cross sectional area than said poles for bridging said gaps.

5. In a motor-control system, a motor, a cumulatively-compound-Wound generator for supplying voltage to said motor, means for variably exciting said generator to cause said motor to operate at speeds corresponding thereto, andadditional means for cumulatively compounding said generator, between restricted load limits, said compounding means comprising a main-field-pole-supportdetermined flux-conducting capacity bridging trarne on said generator, commutating poles on said generator spaced from said frame by non-magnetic gaps, and magnetizable means of predetermined flux-conductlfing capacity bridging said gaps.

6. In a motor-control system, a motor, a generator for supplying a voltage to said motor, `means for Yariably exciting said generator to cause said motor to operate at speeds llt; corresponding thereto, means for cumulatively compounding said generator for obtaining substantially constant-speed regulation of said motor, and means for supplying an additional cumulative component of excita- ;fftion for said generator through a restricted range of load Values.

7. In a motor-control system, a motor, a generator for supplying voltage to said motor, means for variably exciting said generator to cause said motor to operate at speeds corresponding thereto, means for cumulatively compounding said generator for obtaining substantiallyconstant-speedregulationofsaid motor, and means for supplying an additional cumulative component of excitation for said generator throughout a restricted range of load values comprising commutating poles and magnetizing windings therefor.

8. In a motor-control system, a motor, a

.no generator for supplying voltage to said motor, means for Variahly exciting said generator to cause said motor to operate at speeds corresponding thereto, means for cumulatively compounding said generator for obtaining .3 substantially constant-speed regulation of said motor, means for supplying an additional cumulative component of excitation for said generator comprising commutat-ing poles and magnetizing windings therefor, and

4c? means for limiting the cumulative effect of said additional means to a restricted range of load values.

In testimony whereof, I have hereunto subscribed Iny name this 27th day of March,

IVILLIAM F, EAMES.

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