US1929681A - Elevator control system - Google Patents

Description

0a. 10, 1933. W. F. EAMES ELEVATOR CONTROL SYSTEM Original Filed April 5, 1928 INVENTOR lA/ZY/l'd/H FEames.

WITNESSES:

A TO EY Patented Oct 10, 1933 William F. Eames, Edgewood, Pa., assignor to Westinghouse Electric & .Manufacturing Com- Q pany, a corporation of Pennsylvania Original application Aprils, 1928, Serial No..

267,711. Divided and this application Septemher 2, 1931. Serial No. 560,694 a .5 Claims. (cum-223 This application is a division of myapplication Serial 267,711, filed April 5, 1928.

My invention relates to motor-controlsystems and has particular relation. to elevators, hoists and similar machinery.

An object of my invention is to provide a control system for motors wherein a motor may be accurately stopped at anypredetermined point in itstravel, 1

Another object of my invention is to provide a control system for an elevator motor wherein the elevatormay be stopped accurately level with thefloor without overrunning or underrunning the floor.

Another object of my invention is to provide a control system for elevators of the Ward- Leonard type wherein the generator structure is modified to insure accurate speed regulation of the motor at low speeds, independent of loading conditions.

Another object of my invention is to provide a system, as described in the preceding paragraph, wherein the cojmmutating poles of a generator may be so arranged as to achieve an effect of cumulatively compounding the generator atsuch times as the generator is operating atlow 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 of the load upon the elevator, since, in high-speed-elevator work, the accuracy of landing is primarily based upon accuracy of speedregulation, that is, thenormal speed of the elevator should be the same, regardless of the load thereon, when operating under predetermined conditions of control.

To accomplish this result, the Ward-Leonard or variable voltage system of control has been devised wherein variations in the speed of the motor which would normallyoccur with variations in the load upon the elevator are compensated for by means of cumulatively compounding the generator to produce such rising voltage characteristic on the generator as will compensate for the drooping speed characteristic of the motor. .The use of; cumulative compounding of the generator substantially accomplishes this result within rather wide ranges of load. My invention will be described with reference to theaccompanying drawing, wherein,

Figure 1 is a diagrammatic view of an elevatorcontrol system of the Ward-Leonard type.

Fig. 2 is a diagrammatic view of thegenerator showing the arrangement of main-poles andcommutating poles, a portion of which view is in sec-- tion, and I Fig. 3 is a diagrammatic view of a voltage curve obtained by the use of the generator hereinafter 0 described.

Referring "to the drawing, Ihave illustrated, inFig. 1, an elevator carC supported upon a suitable cable Ca which passes overv a hoist drum D to a suitable counterweight Cw. Thehoisting drum D is illustrated as directly coupled to the armature EM of a hoisting motor EM, the field winding EMF of whichis connected for excitation by a suitable source of energy designated by conductor 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 G is provided with a separately excited field winding GF a seriesfield winding GSF, a demagnetizing winding GAF, and a commutating pole winding GC. The generator G is driven by means of asuitable motor M, illustrated as of the shunt-wound type having its armature M and its shunt field windin MF connected across line conductors L1 and L2.

" Thecontrol of the direction andspeed of the elevator car Ca is illustrated as of the usual type whereinup and down-direction switches 1 and 2, respectively, actuated by means of a' car-' switch Cs, control the direction of current supplied to the separately excited field winding GF .5 of the generator G, while a speed switch 3, controlled by the car switch Cs, is. arranged to control the value of the currentsupplied to the field winding GF.

Referring to Fig. 2, the generator G is illus- 0 trated diagrammatically as of the four-pole type, wherein the main poles are designated by the reference characters 5, 6,17 and 8, respectively. Suitably located between the main poles 5, 6, etc.,

I have illustrated commutating or interpoles 9,, 10, 11 and 12, it being understood thatthe number of inter poles corresponds to the number of main poles provided on the generator G. As

is the usual practice in generators of this type, each of the inter poles is provided with a wind- 9 ing (one of which is designated by the character 13) suitably connected in series relation with eachother and with the armature. G.

, :Each of the inter poles 9, 10, etc. may be provided witha core 14 suitably secured to the frame 15 of the generator G by means of abolt 16. The core structure 14 and bolt 16, as well asthe frame structure 15, are all constructed of suitable magnetizable material. Interposedbetween 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 of low reluctance and a relatively large section of high reluctance.

The 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 Cs may be moved in a counter-clockwise direction to energize up-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 up-direction switch 1, conductors 26, 27, contact members 37"of an inductor relay 37, and conductors 39 and to line-conductor L2. Updirection 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 Ll through conductors 29, contact members a of up-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-field winding GF with the addition of voltage induced by the cumulative-compounding effect of the series-field winding GSF. The effect of the winding GSF, since it is in series relation with the armature 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 sufiicient voltage to insure its operating at substantially constant speed for any given value of excitation current supplied to the separately-excited-field winding GF.

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, without intervention on the part of the operator, by means of slow-down inductors 35 and 36 for the up and down directions, respectively, and stopping inductor 37.

When the up-direction switch 1 is actuated to close its contact members a, a self-holding circuit is completed thereby for maintaining the up-direction switch 1 in its actuated position until stopping inductor relay 37 opens its contact members 37. This holding circuit extends from a line conductor L1 through conductor 29, contact members a of up-direction switch 1, conductors 30 and 38, the coil of up-direction switch 1, conductors 26 and 27, normally-closed contact members 37 of stopping inductor relay 37, conductors 39 and 40 to line conductor L2. Hence,

. until stopping inductor relay 37 is actuated, the

up-direction switch will remain operative and the car will continue its upward movement, even though the car switch Cs is centered.

If 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 to speed switch 3 by way of a circuit which extends from the line conductor Ll through conductors 20 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 line conductor 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 of excitation current supplied to the separately-excited-field winding GF. Hence, the elevator motor EM will accelerate and operate at the speed corresponding to this new value of field excitation.

When speed switch 3 is actuated, it completes a self-holding circuit for itself, which circuit extends from a line conductor L1 through conductors 29 and 46, contact members I) of speed switch 3, conductor 47, contact members 35' of up slow-down inductor 35, conductor 48, contact members 36 of slow-down inductor relay 36, conductors 49 and 42, the coil of speed switch 3 and conductors 43 and 40 to line conductor L2.

When it is desired to stop the elevator car, the car switch Cs will be returned to its central or illustrated off position. By reason of the holding circuits for up-direction switch 1 and speed switch 3, previously described, the car will continue its upward motion at high speed. Centering the car switch Cs, however, closes a circuit for energizing the actuating coils of inductor relays 35 and 37. This circuit extends from line conductor L1 through conductors 20 and 21, contact members 22, 23 and 50 on car switch Cs, conductor 51, the coil of stopping inductor relay 37, conductor 52, the coil of slowdown inductor relay 35, conductor 53, contact members (1 on up-direction switch 1 and conductors 54, and 40 to line conductor L2.

As the car approaches the floor at which it is desired to stop, the slow-down inductor relay 35 will be brought adjacent an inductor plate 35 (one of which plates is provided at each of the fioors past which the elevator moves) and the inductor relay 35, now energized, is actuated to open its contact members 35'. Opening contact members 35 releases the holding circuit for speed switch 3, which switch is restored to its normal condition, opening 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 supplied to field winding GF.

As the car approaches more closely to the desired floor, stop inductor relay 37 will be brought adjacent an indicator plate 37 associated therewith (one of which also is located adjacent each of the floors past which the car moves) and relay 37 will be caused to open its contact members 37' to release the holding circuit for up-direction switch 1. Up-direction switch will, when deenergized, open the circuit for the partly excited field 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 normal high speed to a landing speed prior to the final stopping of the car. For acparent that the speed of the car at this low matterated is .fixed by the relative positioning of the inductor plates and 37".

It will be observed that, under the conditions just described, contact members c of up-direction, switch 1 will complete a circuit connecting the demagnetizing-field winding GAF across the terminals of the armature EM of the elevator motor EM. ,The demagnetizing-wi'nding GAF is so wound and arranged that, when connected across the terminals of the motor armature EM, the circulating current in the armature EM will excite the winding GAE to oppose-the efiectof the separately excited and series field windings GF and GSF to thus reduce the voltagev of the generator to zero and to thereby bring the elevator motor to a stop. It is 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 generator-voltage values are plotted as ordinates, against generator load values, expressed in percentages of full-load ourrent, as abscissaa. The curves illustrate the variationsin terminal voltage from a negative or overhauling load of approximately full load to full load. The no-load voltage is shown as approximately 15 volts, which, as hereinbefore stated, corresponds to atypical landing speed i of an elevator motor. Curve 56 is typical of a generator provided with normal compounding means, while curve 5'7 illustrates the improved voltage regulation effected in the practice of my invention.

Referring to curve out which the slope of the curve is substantially constant as the major portioni of the load range, and to that portion of the load range throughout which the slope of the curve departs from the desired or substantially constantvalue as the restricted portion of the load range. Since the. slope of curve 56 throughout the restricted portion of the load range differs from that throughoutthe major portion of the load range, it will be apparent that a degree of compounding effective to produce a desired landing speed of the elevator motor throughout the major portion of the load range, will be ineffective to produce the same motor speed throughout the restricted portion thereof. As 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 generatoninthat the variations 56, it will be observed that, throughout the load range from 10% to 100%" in generator voltage are substantially proportional to the generator load throughout the entire load range. By organizing a generator in accordance withmy invention, the voltage character- 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 of excitation, the value of which varies as a function of the generator load throughout the restricted portion of theload range, and remains substantially constant throughout the major portion thereof. The manner in which the described construction of the commutating poles of the generator is eifectiveto produce thisresult 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 by the current in the armature windings. 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 beprematurely reduced to zero and reversed. ,The reversecurrent 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 fromthe flux of the main field windings and thus exerts a compounding action on the generator. It follows that this compounding action is cumulative when the load is positive, and differential when the load is negative, since thecommutating 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 beobserved that the magnetic circuit for the flux of the windings thereof 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 a given increase in load current will produce a given increase in commutating-pole flux. If, now, the bolt is permitted to saturate at a predetermined value of 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 atwhich the slope of curve 56 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 thesaturated condition of a portion of its magnetic circuit, the flux of the commutating poles increases less rapidly, or,

i io

increases as such a function of theload that the additional component of generator excitation 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 substantially constant slope throughout the entire load range.

It will, therefore, be observed that, by utilization of the structure just described, the inaccuracy of speed regulation at low speeds is corrected without disturbing the speed regulation normally imposed by the compounding of the generator G by means of the series field winding GSF.

In actual practice, it has been observed that the arrangement just described achieves an effect of correcting the inaccuracy of speed regulation to the extent of at least 50% andthis amount of correction is readily appreciated when the con-. trol system herein described is applied to elevators having a device for 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. 731,921, 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 from the floor, regardless of the load on the elevator, causes the car to stop substantially level with the fioor without further attention on the part of the attendant. In actual test, such systerns stop the car level with the floor within a half inch, regardless of load. However, by the use of the system for providing additional com-' pounding of the generator, as herein described, such inaccuracy can be reduced to less than onefourth 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 pole 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.

In the present application, I do not claim a control system arranged to accommodate a generator organized in accordance with the present invention, since this subject-matter is claimed in my application, Serial No. 267,711, filed April 5, 1928, hereinbefore identified.

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

I claim as my invention:

1. In a generator for supplying a variable load, said generator having a fixed zone of commutation, means for exciting said generator, means including commutating poles and magnetizing windings therefor disposed to supply one componentof fiux for commutating purposes, and to supply another component of flux to vary the voltage of said generator in accordance with the value of said load, and means responsive to said lead to limit the cumulative effect of said windings on the voltages of said generator to a restricted range of load values.

2'. In a generator for supplying a variable load, said generator having a fixed zone of commutation, means for exciting said generator, commutating. poles and magnetic circuits associated therewith, magnetizable windings on said poles disposed to supply one component of flux for commutating purposes, and an additional component of flux to vary the voltage of said generator, and means responsive to the load on said generator to render said commutating pole windings effective to vary said generator voltage in accordance with said load throughout a predetermined range of load values.

3. In a generator for supplying a variable load, said generator having a fixed zone of commutation, means for exciting said generator, commutating poles and magnetic circuits associated therewith, magnetizable windings on said poles disposed to supply one component of flux for commutating purposes, and means disposed in the magnetic circuits of the flux of said commutating poles to render said commutating pole windings effective to vary said generator voltage in accordance with said load throughout a predetermined range of load values.

4. In a generator for supplying a variable load, said generator having a fixed zone of commutation, means for exciting said generator to cause said generator to develop a voltage, means comprising commutating pole windings to cause said generator to develop an additional component of voltage proportional to said load, and means for limiting the effect of said last named means to a predetermined range of load values.

5. In a generator for supplying a variable load, said generator having a fixed zone of commutation, a first means for exciting said generator to cause said generator to develop a voltage, a second means for causing said generator to develop an additional component of voltage proportional to said load, said second means comprising commutating pole windings and means to define a magnetic circuit for the flux thereof, and means disposed to control the reluctance of said circuit to limit the efiect of said second means to a predetermined range of load values.

WILLIAM F. EAMES.

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