US1985060A - Elevator control system - Google Patents

Description

Dec. 18, 1934. D. SANTINI 5,

- Q 'ELEVATORICONTROL SYSTEM Filed Oct. 29, 1932 2 Sheets-Sheet 1 WITNESSES: INVENTOR 0 24 S Dam'lo Santini.

v BY

Mum ,m H

Dec. 18, 1934.- $ANT|N| 1,985,060

ELEVATOR CONTROL SYSTEM File OOC- 29. 1932 2 Sheets-Sheet 2 WITNESSE S: INVENTOR Patented Dec. 18, 1934 UNITED STATES PATENT OFFICE Application October 29, 1932, Serial No. 640,180

1 Claim.

My invention relates to elevator control systems and has-particular relation to elevator control systems embodying means for overcoming the effects of residual magnetism in dynamo- 5 electric devices employed therein,

My invention will be described as applied to an elevator control system of the well known Ward- Leonard or variable-voltage type but it should be understood that it is not necessarily limited to this particular type of control system.

I have found that in a multi-speed motor control system of the variable-voltage type, in which an. elevator car is accelerated to a high speed for long runs and an intermediate or lower speed for shorter runs, thatif the initial run of an elevator car immediately after a reversal in its direction of movement is a short run in which it attains only an intermediate speed, the speed of the elevator car is less than is desirable.

I have concluded that the diminished speed of the car immediately after reversal is due to the opposing effect of the residual magnetism in the field cores and other magnetic structure of the generator of the variable-voltage system. That is, although the separately excited shunt field winding of the main generator which supplies power to the elevator motor is energized to the same degree before and after reversal, the speed of the elevator car is less after reversal than before, due to the opposing magneto-motive force exerted by the residual magnetism against the magneto-motive force set up by the current flowing through the shunt field winding. The voltage generated by the main generator and supplied to the elevator motor is thus diminished from a predetermined voltage which is necessary to actuate the motor to drive the elevator car in accordance with a predetermined speed characteristic.

The ultimate result of the effect of the residual magnetism is that the length of time between the starting and stopping of an elevator car for a short run immediately after reversal is increased an appreciable amount over the length of time which should be consumed in order that the car follow a predetermined speed characteristic.

In order to overcome this disadvantageous effeet I propose to over-excite the generator shunt field winding a predetermined amount necessary to compensate for, or overcome, the efiect of the opposing magneto-motive force exerted by the residual magnetism, in the event that the initial run after reversal is a short run in which tliz'elevator car does not attain maximum speed.

Any suitable means for over-exciting the sepa'- rately excited shunt field winding of the generator may be employed, such as short-circuiting a portion of the resistance connected in series-circuit relation or potentiometer relation with the shunt field winding or employing a voltage com pounding means, such as a regulating generator, the voltage from which is suitably controlled to increase the degree of compounding normally employed to energize the shunt field winding.

It is an object of my invention, therefore, to compensate for the efiect of residual magnetism in the field cores of dynamo-electric devices employed in elevator control systems.

It is a more specific object of my invention to vary the degree of excitation of the shunt field winding of a generator of a variable voltag'e type of control in order to compensate for the eifect of residual magnetism in diminishing speed, in the event of the operation of the elevator car at an intermediate speed immediately subsequent to a reversal in the direction of movement of the elevator car.

Other objects of my invention will be apparent from the following description and explanation of the operation of my invention when read in connection with the accompanying drawings, wherein Figure 1 is a diagram illustrating one embodiment of a control system to which my invention is adapted, and

Fig. 2 is a view showing an elevator car having inductor relays thereon and a complete set of stationary inductor plates for one floor.

Referring to Fig. 1, a suitable driving motor DM, illustrated as of a three-phase induction type and connected to alternating current supply conductors m, n and 0 through a suitable switch 11, is employed to drive the armature of a directcurrent generator G, the armature winding GA of which is connected in closed-loop circuit relation with the armature winding MA of a motor M for driving the. elevator car C.-

The generator G is provided with a separately excited shunt field winding GF and a series field winding GSF which is connected in series-cir cuit relation with the armature winding GA. The motor M is provided with a separately excited shunt field winding MF which is suitably controlled.

The elevator car C and its counterweight Cw are suitably supported by a cable Ca. which extends around a drum D rotated by the motor M.

-- The motor M is provided with a suitable electrol-magnetic brake B, comprising a brake drum BD which is secured to the shaft of the armature of the motor, and a brake shoe Bs which is biased into frictional relationship with the drum EU in a suitable manner and released from engagement therewith by a release coil or solenoid Rs which is energized whenever the elevator motor is actuated to start the car.

, Direction relays 1 and 2, corresponding to the upward and downward travel of the elevator car, respectively, and energized by the operation of a car switch OS on the elevator car, are employed to reversibly control the connection of the generator shunt field winding GF to a pair of conductors Li and L2 which supply suitable directcurrent potential.

Acceleration and deceleration of the elevator car is effected by means of suitable resistors R1 and R2 connected in series-circuit relation with the generator shunt field winding GF, the resistors being controlled respectively by means of relays GR l and 6R6.

A high speed inductor relay 3R, an intermediate speed inductor relay 2R and a stopping inductor relay 1R are suitably disposed on the elevator car C, as shown in Fig. 2, for cooperating in succession with a suitably disposed group of inductor plates at each floor which comprise the up-direction high-speed inductor plate 3U, the up-direction intermediate-speed plate 2U, the Lip-direction stopping plate 1U, the down-direction high-speed plate 3D, the'down-direction intermediate-speed plate 2D and the down-direction stopping plate 1D.

Inductor relay 3R is provided with a suitable energizing coil 3L and with suitable up-direction contact members BUL and down-direction contact members 3DL, the contact members being selectively actuated to open when the relay, with its coil energized, comes into adjacent relation ergized, comes into adjacent relation with the intermediate speed inductor plates 2U or 2D respectively. The contact members 2UL and 2DL of relay 2R, control the relay GR4 and, when opened, efiect the deenergization thereof to cause the reinsertion of resistor R1 in series-circuit relation with the generator shunt field winding GP to thereby eiiect the deceleration of the elevator car to low speed.

Inductor relay IR is provided with an energizing coil 1L and with up-direction contact members lUL and down-direction contact members lDL, the contact members being selectively actuated to open when the relay, with its coil energized, comes into adjacent relation with the stopping inductor plates 1U or 1D respectively. The contact members lUL and lDL of relay 1R are connected respectively in series-circuit relation with the energizing coils of direct'on relays 1 and 2 and, when opened, efiect the deenergization of the corresponding relay to interrupt the circuit for energizing the generator shunt field winding A regulating generator RG- is provided which; has an armature Winding RA and a field winding RSF which is connected in the loop circuit, including the armature windings GA and MA of the generator G and the motor M respectively. The armature winding of the regulating generator R6 is connected in series circuit relation with the generator shunt field winding G15 and is driven at a constant speed by a suitable motor, not shown, to generate a voltage in proportion to the amount of current flowing in the loop circuit connecting the armature windings of the generator G and the motor M.

A suitable potentiometer resistor PR, which is connected across the brush terminals of the regulating generator RG is provided for varying the voltage in the energizing circuit of the generator field winding GF as desired,

A suitable resistor R is connected in shunt relation to the generator field winding GF and the potentiometer resistor PR for the purpose of completing a local energizing circuit for the field winding GF from the potentiometer as'a source of energy.

A voltage responsive relay 31, of well known construction, is connected across the brush terrn'nals of the motor M in series-circuit relation with a suitable resistor r and is designed to be actuated only after the motor attains a predetermined speed such as the intermediate speed.

Relay 31 controls the energization of the high.

speed relay GR6 and unless relay 31 is actuated,

relay (3R6 cannot be energized to cause the elevator car to accelerate to high-speed.

An additional resistor R3 is connected in seriescircuit relation with the shunt field winding GF and a relay 3 is provided which is adapted to control this resistor to cause it to be short-circuited out of the energizing circuit of the generator field winding GP, in the event that the initial run of the elevator car immediately after a reversal in its direction of movement is such as not to enable the car to attain high-speed.

A pair of relays U and 80 D, which are controlled by the direction relays l and 2, are employed to control the energization of the relay 3 which is adapted to be'initially energized upon the energization of high-speed relay 6R6.

The relay 3 also controls the tap connection to the potentiometer resistor PR and causes a greater portion thereof to be included in series-circuit relation with the generator field winding GB in the event that the initial run of the elevator car immediately after reversal in its direction of travel is such that it does not attain high speed.

Although I have shown relay 3 as controlling both the resistor R3 and the potentiometer resistor PR for the purpose of over-exciting the generator field winding to a predetermined amount necessary to overcome the opposing effect of the residual magnetism in the field cores of the generator G, it should be understood that either one may be suitably adapted to separately effect the same result as when both are employed together.

Furthermore, while I have shown a regulating generator RG as provided with only a single field RSF, it should be understood that it may also be provided with a differential field winding in the manner disclosed in the copending application of Kenneth M. White and George K. Hearn, Serial No. 489,766, filed October 20, 1930, issued October 25, 1932, as Patent No. 1,884,446, and assigned to the Westinghouse Electric Elevator Company.

My invention may best be understood by describing the various steps involved in a typical material is secured to a conducting sector 12 tor L2.

which is suitably pivoted at 13, and thus during the movement of the car-switch handle the sector 12 is moved thereby to engage a stationary contact finger l5 and complete a circuit for energizing the coil of up-direction relay 1, which circuit extends from supply conductor L1 through conductor 21 to sector 12, thence through contact finger 15, conductor 22, coil of relay 1, conductor 23, contact members lUL of relay 1R, conductor 24, car gate-switch g, hatchway door-interlock switches d, in series, and safety switches ss, in series, to supply conductor L2.

The energization of relay 1 effects the closing of the normally open contact members a, b and c and the opening of the normally closed contact members d thereof. The opening of contact members at of relay 1 interrupts a circuit for energizing the coil of relay 80 U which, as will be subsequently explained, is energized at this time, the circuit for energizing relay 80 U extending from supply conductor L1 through conductor 25, contact members d of relay 1, conductor 26, coil of relay 80 U,

conductor 27, normally closed contact members a of relay 80 D and conductor 29 to supply conduc- Ihe reclosing of normally closed contact members a of relay 80 U, as a result of the deenergization thereof, completes a circuit for energizing the coil of relay 80 D, which circuit extends from supply conductor L1 through conductor 29, normally closed contact members d of relay-2, con ductor 30, contact members a of relay 80 U, conductor 30a, coil of relay 80 D and conductors 32 and 28 to supply conductor L2. The effect of the deenergization of relay'80 U and the energization of relay 80 D will be explained hereinafter.

The closing of contact members a of relay 1 completes a circuit for energizing the release coil Rs of the brake B on the motor M, which circuit extends from supply conductor L1 through conductor 33, contact members a of relay 1, conductors 34 and 35, brake coil Rs and conductor 36 to supply conductor L2.

The closing of contact members b and c of relay 1 completes a circuit for energizing the separately excited shunt field winding GF of the main gen= erator G and the generator, therefore, supplies an initial voltage to the armature winding MA of the motor M suflicient to start elevator car at low speed immediately upon the release of brake B. The circuit for energizing field winding GF, in this case, extends from supply conductor L1 through conductor 37, contact members b of relay 1, conductor 38, field winding GF, conductor 39, normally closed contact members I) of relay 3,

. armature winding of generator RG, conductor 40,

i tors 44 and 45 to the point 46 whence it extends through resistors R2 and R1 to supply conductor L2.

A local circuit, including the generator shunt field winding GE is also completed, which extends from one brush terminal of the armature of the regulating generator RG through conductor 40, resistor R, conductors 81 and 38, field winding GF, conductor 39 and contact members I) of relay 3, back to the brush terminal of opposite polarity on the armature winding of generator RG. A current flows in this local circuit which is proportional to the current flowing in the loop-circuit connecting the armature windings GA and MA of the generator G and motor M respectively, and

depending upon the direction of fiow of current in the loop circuit, increases or decreases the excitation of the generator field winding with respect to that which would occur due only to the other excitation.

As a result of the energization of the field winding GF, the generator G generates an initial voltage for supplying power to the motor M and causing it to drive the elevator car at low speed.

Although the sector 12 of the car switch CS only momentarily engaged the contact finger 15 and although it is no longer in engagement therewith, the circuit for energizing the coil of relay 1 is maintained through a self-holding circuit established by the closing of normally open contact members e of relay 1 which are connected in parallel-circuit relation with sector 12 and contact finger 15 of the car switch CS from supply conductor L1 to the coil of relay 1.

The car switch CS is so designed that, when its handle is moved into the position of its clockwise extremity of movement, the sector 12 remains in contacting engagement with contact fingers 16 and 1'7. The engagement of sector 12 with contact finger 16 completes a circuit for energizing the coil of relay (3R4, which extends from supply conductor L1 through conductor 21 to the sector 12 of the car-switch, thence through contact finger 16, conductor 47, normally open contact members g of relay 1, conductor 48, contact members 2UL of inductor relay 2R, conductors 49 and 50, coil of relay GR4 and conductor 51 to supply conductor L2. Normally open contact members 0 of-relay (5R4, when closed by the energization of the relay, complete a self-holding circuit for maintaining the energization of the relay independently of the position, of the car-switch CS. Contact members 0 of relay GR4 are connected in parallel-circuit relation with sector 12 and contact finger 16' between supply conductor L1 and the contact members g of relay 1.

The closing of normally open contact members a of relay GR4 completes a short-circuiting connection around resistor R1 and thus, in effect, removes the resistor R1 from the circuit for energizing the generator shunt field winding GF. As a result of the decreased resistance in series with the field winding GF, a greater current flows through the field winding and increases the excitation of the field of the generator G so that the latter generates a greater voltage and thus the motor M is accelerated to cause the elevator car to travel at a predetermined intermediate speed.

Just prior to the time that the elevator motor M attains the intermediate speed, the voltageresponsive relay 31 is energized to close its contact members and thereby complete a circuit for energizing the coil of relay GR6, which circuit extends from supply conductor L1 through conductor 21, section 12 or the car switch, contact finger 1'7, conductor 52, normally open contact members it of relay 1, conductor 53, contact members 3UL of inductor relay 3R, conductors 54 and 55, contact members ofrelay 31, conductor 56, coil of relay 61% and conductor 57 to supply conductor The closing of normally open contact members at of relay GRG, upon the energization thereof, completes a sell-holding circuit which is connested in parallel-circuit relation with sector 12 and contact finger 1'? of the car switch CS between supply conductor L1 and contact members it of relay 1, so that the relay is maintained energized independently of the en agement of sector 12' and contact finger l'l.

The closing of normally open contact members b of relay G136 completes a circuit for energizing the relay 3 which circuit extends from supply conductor Ll through conductor 56, coil of relay 3, conductor contact members i) of relay GRG and conductor to supply conductor L2.

The closing of normally open contact members d, as a result of the energization of relay 3, coinpletes a self-holding circuit for maintaining the relay energized independently of contact memhers b of relay GRS, which holding circuit extends iroin supply conductor L1 through conductor 58 and the coil of relay 3 thence through conductors 59 and 61, contact members it of relay 3, conductors 62 and 63, contact members i) of relay 8013, which were closed as previously described, and conductors 64 and 65 to supply conductor L2.

The opening of normally closed contact memhers a of relay 3 removes the short-circuiting connection around resistor R3 and thus reinserts the resistor R3 in series-circuit relation with the generator shunt field winding Similarly, the opening of normally closed contact members i) and the closing of normally open contact menu ers c of relay 3 reduces the amount of the potentiometer resistor PR included in series-circuit relation with the generator field winding GF. The efiect or" reinserting the resistor R3 and/or decreasing the amount of the potentiometer resistor PR efiective tocompound the excitation of the field winding GF would be to effect a reduction in the speed of the elevator car, except for the fact that the resistor R2 is simultaneously short-circuited by the closing of the normally open contact members a of relay The normally open contact members a of relay (EH6, when closed as a result of the energization of the relay, complete a short-circuit connection around the resistor R2 and thus cause the current through the generator field winding GF to be still further increased, which ultimately results in the elevator motor M being accelerated to drive the elevator car 1 at its maximum or high speed.

As long as the elevator operator desires to cause the elevator car to continue to travel at high speed, he holds the handle of the car switch in its extreme displaced position in a clockwise direction. As he approaches the floor at which he desires to stop the elevator car, in this case assumed to be the upper terminal floor, the operator centers the car-switch, that is, returns the handle of the car-switch to its central position.

The sector 12 of the car-switch reengages the contact finger 14 when the car-switch handle is returned to its central position, and a circuit is thereby completed for energizing the coil 3L of inductor relay 3R, which circuit extends from supply conductor L1 through conductor 21, sector 12 of the car-switch, contact finger l4, conductors 66 and 6'7, normally open contact members J of relay 1, conductor 68, coil 3L of inductor relay BR and conductor 69 to supply conductor L2.

The elevator car continues to travel at high speed until the inductor relay 3R on the car comes into closely adjacent relation to the high.

bers 3UL of inductor relay 3R ed to an open position and previously traced, for energi GRfi. As a result, relay GEE; is deenergized the contact members a thereof are opened to move the short-circuit connection around resistor R2 and to effect its reinsertion in the circuit of the generator field winding GE. A reduction in. the current through the enerator field winding GF is thus effected and the motor is decele tted to cause the car to travel at the interine speed. The opening of contact members h of lay GRG is without effect, since the relay is maintained energized through the holding circuit previously traced.

The opening of contact members 01 of relay GR6 is likewise without effect, since the selfholding circuit for relay which is rnaintained thereby, has been otherwise interrupted by the opening of contact members ZUL of inductor relay 3R.

The reclosing of normally closed contact menihers c of relay (3R6, however, completes a circuit for energizing the coil 2L of inductor relay 2B, which circuit extends from supply conductor Ll through conductor 21, sector 12 on the car switch CS, contact finger i l, conductors 66 and 67, con tact members f of relay 1, conductors 68 and '70, coil 2L of inductor relay 2R, conductor 71, contact members 0 of relay (EEG and conductor 72 to supply conductor L2.

As the elevator car continues to travel at the intermediate speed, relay 2R comes into closely adjacent relation tothe intermediate-speed updirection inductor plate 2U, corresponding to the upper terminal floor, and the contact members 2UL thereof are thus actuated to an open position to interrupt the circuit, previously traced, for energizing the relay (:Rei.

The opening of contact members a, as a result of the deenergization of relay (3R4, removes the short-circuiting connection around resistor R1 and this results in a further decrease of the current through the generator field winding GP and ultimately in the deceleration of the elevator car to low speed.

The opening of contact members 0 of relay GEM is without effect. since the holding circuit maintained thereby for energizing relay CR4; has been previously opened by the opening of contact members 2UL.

The reclosing of normally closed contact memhers I) of relay GRl completes a circuit for energizing the coil 1L of inductor relay 1R, which circuit extends from supply conductor Ll through conductor 21, sector 12 on the car-switch, con tact finger l4, conductors 66 and 6'7, contact ll'lGlTihers f of relay 1, conductors 63 and 73, coil 1L of inductor relay 1R, conductor 74, contact memhers I) of relay GR l and conductor '75 to supply conductor L2.

The elevator car continues to travel at low speed until the relay 1R comes into closely adjacent relation to the up-direction stopping inductor plate 1U for the upper terminal. floor, at which time contact members lUL of inductor relay 1B are caused to be opened and interrupt the circuit, previously traced, for energizing the up-direction relay 1. As a result of the deenergization of relay 1, the circuits, previously traced, for severally energizing the generator shunt field winding 62F and the release coil Rs of the brake B, are interrupted with the results that the elevator car stops and the brake B is applied to the motor M to maintain the elevator car in position at the terminal floor in exact alinement therewith.

The opening of normally open contact members I of relay 1, as a result of the deenergization of relay 1, interrupts the several circuits, previously traced, for energizing the coils 1L, 2L and BL of the inductor relays and thus tlt'coils become deenergized.

' Now let it be assumed that the operator desires to make a so-called one floor run, that is, descend to the fioor immediately below the terminal floor. To effect such movement of the elevator car, the

operator may move the car-switch handle in a counter clockwise directiomhold it momentarily in its extreme displaced position and then return it to its central positidjn. The engagement of sector 12 on the cars-switch with the stationary contact finger 18 completes a circuit for energizing down-directional relay 2, which circuit extends from supply conductor L1 through conductor 21, sector 12, contact finger 18, conductor '76, coil of relay 2, conductor 77, contact members lDL of inductor relay 1R, conductors 78 and 24, and thence through gate-switch g, door-interlock switches d and safety switches ss, in series, to supply conductor L2.

The normally closed contact members d of relay 2, when opened as a result of the energization of the relay, interrupt the circuit for energizing relay 80 D, previously traced, and the self-holding circuit for maintaining relay 3 energized is thus interrupted by the opening of contact members b of relay 80 D. The reclosing of contact members a of relay 80 D completes a circuit for energizing relay 80 U, as previously traced, but due to the fact that the contact members (I of relay 3, have already opened, the closing of contact members I) of relay 80 U is ineffective to complete a circuit for energizing relay 3. Relay 3, therefore; becomes and remains vdeenergized. Contact members a of relay 3, when closed as a result of the deenergization of the relay, complete a short-circuiting connection around the resistor R3 and the contact members b of relay 3 reclose to connect the armature winding of generator RG in series-circuit relation with the generator field winding GF.

When contact members b and c of relay 2 close as a result of the energization of the relay, they complete a circuit for energizing the generator field winding GF in a reverse direction to that effected by the closing of contact members 22 and c of relay 1 so that the voltage generated by the generator G is of reverse polarity and the motor M is thus caused to rotate in such a direction as to move the elevator car downwardly.

The circuit for energizing the generator field winding GF, as established by the closing of contact members I) and c of relay 2, extends from supply conductor L1 through conductor 79, contact members of relay 2, conductors 80 and 40, armature winding of generator RG, contact members b of relay 3, conductor 39, field winding GF, conductors 38, 81 and 82, contact members b of relay 2 and conductors 83 and 41 to the point 42, thence through conductor 43, contact members a of relay 3 and conductors 44 and 45 to the point 46, thence through resistors R2 and R1 to supply conductor L2.

Contact members a of relay 2 are connected in parallel-circuit relation-with contact members a of relay 1 and thus, when contact members a of relay 2 are closed as a result of the energization of the relay, the release coil Rs of the brake B on the motor M, is energized through a circuit substantially identical with that previously traced therefor.

The elevator car is thus initially caused to travel at low speed in a down direction. It is to be noted that my invention embodies the feature, just described, whereby the resistor R3 is short circuited and/or the connections to the potentiometer resistor PR are changed. The effect of short-circuiting the resistor R3 and/or changing the connections to the potentiometer resistor PR is to overexcite the generator field winding to a predetermined amount necessary to overcome the opposing magneto-motive force exerted by the residual magnetism in the field coils of the generator G, which residual magnetism exerts a magneto-motive force in opposition to the magneto-motive force created by the current flowing through the generator field winding GF. As a result, therefore, the generator G generates a normal voltage, that is, such a voltage as will cause the elevatormotor M to drive the elevator car at a predetermined low speed.

Although the car-switch handle is centered, the energization of relay 2 is maintained by norreally open contact fingers e of relay 2 which complete a self-holding circuit in parallel-circuit relation with the car-switch sector 12 and contact finger 18 between supply conductor L1 and the coilof relay 2'.

As a result of the engagement of sector 12 on the car switch with the contact finger 19, a circuit is completed for energizing relay 6R4, which extends from supply conductor L1 through conductor 21, sector 12, contact finger l9, conductor 85, contact members 9 of relay 2, conductor 86, contact members 2DL of inductor relay 2R, conductor 50, coil of relay GR4 and conductor 51 to supply conductor L2.

Contact members a of relay (3R4, when closed complete a short-circuiting connection around resistor R1 which results in an increase in current through the generator field winding GE and ultimately in the acceleration of the motor M to drive the elevator car at the intermediate speed. Normally open contact members 0 of relay GR4 complete a self-holding circuit for the relay as previously described, since they are connected in parallel-circuit relationwith the sector 12 and contact finger 19 of the car switch CS. The elevator car is thus maintained at intermediate speed regardless of the centering of the car switch handle.

Due to the fact that the car switch handle was centered by the operator almost immediately after its displacement from the central position, relay GRS cannot become energized because the high-speed circuit for energizing the coil of relay GR6 is not completed by the mere engagement of sector 12 and contact finger 20 of the car switch. Although the sector 12 and contact finger 20 are momentarily in engagement, if the contact members of the voltage responsive relay 31 have not been previously actuated to a closed position, due to the fact that the motor M has not accelerated sufiiciently, the relay GR6 cannot become energized.

The elevator car cannot, therefore, travel a a speed greater than the intermediate speed, and

it continues to travel at the intermediate speed until the inductor relay 2R on the elevator carcomes into closely adjacent relation to the downdirection intermediate-speed inductor plate 2D.

At such time, the contact members 2DL of relay 2R. are actuated to an open position and thereby interrupt the circuit, previously traced, for energizing relay GRi. Relay GR4 is thus deenergized and the contact member a thereof opened to remove the short-circuiting connection around resist-or R1. The re-insertion of resistor R1 in the circuit of the generator field winding reduces the amount of current flowing therethrough and ultimately results in the deceleration of the elevator motor to drive the elevator car at lowspeed.

The elevator car continues to travel at low speed until the inductor relay 1R on the elevator car comes into closely adjacent relation with the down-direction stopping inductor plate 1D for the ninth floor. Contact members 1131.. of relay 1R are thereby actuated to an open position to interrupt the circuit, previously traced, for energizing relay 2. The opening of contact members a. b and c of relay 2 interrupt the circuits previously traced for energizing the release coil Rs and the generator field winding GF. As a result, the elevator motor stops the elevator car in exact alinement with the ninth floor and the brake B is applied to maintain the car in position thereat.

The opening of normally open contact members f of relay 2, as a result of the deenergization of relay 2, interrupts the circuit for energizing the coils 1L, 2L, 3L of the inductor relays 1R, 2R and 3R, respectively. It will thus be seen that the inductor relays are energized only during the landing period and at all other times no power is required for their energization.

Now let it be supposed that the operator desires the car to travel downwardly to the lower terminal floor, he may move the handle of the carswitch in a counter-clockwise direction into its extreme displaced position, holding it there until such time slightly before the elevator car arrives at the landing zone defined by the inductor plates 3D, 2D and 1D for the lower terminal landing at which time he may center the car switch.

' The operation of the control system is the same as just previously described for the movement of the car from the top terminal floor to the next lower floor up until the time that the elevator car attains the intermediate speed. Due, however, to the fact that the car-switch handle is maintained in its displaced position, sector 12 remains in engagement with the contact finger 20 and thus, upon the closing of the contact members of the voltage-responsive relay 31, a circuit is completed for energizing the relay GR6, which circuit extends from supply conductor L1 through conductor 21, sector 12, contact finger 20, conductor 88, contact members h of relay 2, conductor 89, contact members 3DL of inductor relay 3R, conductor 55, contact members of relay 31, conductor 56, coil of relay GR6 and conductor 57 to supply conductor L2. 1

Contact member a of relay GRG complete a short circuiting connection around resistor R2 to accelerate the elevator car to high speed in the ,manner similar to that described for the up-di- 'rection of travel of the car. Contact members d of relayGRG, when closed by the energization of .the relay, complete a self-holding circuit for maintainingthe relay energized due to the fact that they are connected in parallel-circuit relation with the contact segment 12 and the contact finger 20 of the car switch.

When contact members b of relay GRG close, due to the energization thereof, relay 3 is-again energized through the circuit, as previously traced,

and contact members a, b and c of relay 3 function as before to remove the short-circuiting connection from resistor R3 and reduce the amount of the potentiometer resistance PR in series-circuit relation with the generator field winding GF.

The closing of contact members (1 of relay 3 completes a self-holding circuit for maintaining the relay energized, which circuit extends from supply conductor L1 through conductor 58, coil of relay 3, conductors 59 and 61, contact members at of relay 3, conductor 62, contact members b of relay U and conductor 65 to supply conductor L2.

It will thus be noted that in the case of the elevator car attaining only intermediate speed, the resistor R3 becomes short-circuited and the connections to the potentiometer resistor PR are so changed that the armature winding of generator RG is connected in series-circuit relation with the generator field winding GF whereas when the elevator car accelerates to high speed, the resistor R3 is not short-circuited and only a portion of potentiometer resistor PR is connected in series circuit relation with the generator field winding GF instead of the armature winding.

1 have found that in the case of the elevator car accelerating to the highest speed, the degree of excitation of the generator field winding GF is sufiicient to reverse the residual magnetism in the field cores of the generator G so that its effect thereafter is not subtractive in its eflect on the generator voltage until such times as the excitation of the generator shunt field winding is again reversed.

The car continues to travel at high speed until such time as the operator centers the car switch whereupon the inductor relay coil 3L is energized and the sequence of operations for effecting the deceleration and stoppingof the elevator car at the lower terminal floor is effected by the successive opening of thecontact members BDL, 2DL and lDL of the inductor relays 3R,'2R and 11?. respectively, in the manner substantially similar to that already described for the stopping of the car at the upper terminal landing.

The employment of relay 3 for the purpose of controlling resistor R3 and the potentiometer resistor PR and thereby over-exciting the generator field winding GF to a predetermined amount necessary to overcome the opposing effect of the residual magnetism in the field cores of the gendue to the effect of the residual magnetism, over that required to cause the elevator car to travel in conformity with a predetermined speed characteristic for a short run such as that between two adjacent floors.

It should be understood that, while I have disclosed a control system adapted to cause the elevator car to travel at only three speeds, namely, low speed, intermediate speed and high speed, it may readily be adapted to cause the car to travel at a greater number of diiferent speeds. It should, furthermore, be understood that additional relays corresponding to relay 3 may be employed for the purpose of functioning in a similar manner as between an intermediate speed andv another neaacco lower intermediate speed so that the excitation of the generator field winding may be further controlled for the purpose of varying the extent of over-excitation of the generator shunt field winding, depending upon whether the elevator car accelerates to one intermediate speed or another intermediate speed.

In conclusion, therefore, it will be seen that l have disclosed a control system embodying means for compensating for the eilect of residual magnetism in dynamo-electric devices employed in the system, whereby consistent conformity of a motor speed curve with a predetermined soeecl curve is obtained regardless of whether the motor accelerates to an intermediate speed. or maximum speed immediately after a reversal in its direction or" movement. Obviously, my invention is not limited in scope, merely to elevator applica tions, although it is especially useful in connec tion therewith.

It should he understood that my invention is capable of various modifications and adaptations Without departing from the spirit thereof and that l. do not desire to limit the scope thereof except as necessitated toy the prior art and as defined by the appended claim.

I claim as my invention:

in a control system fora motor, a generator in cluding a field winding for supplying power to said motor, a reversible circuit associated with said winding, resistance in said circuit, a control ler for said motor including means for reversing said field winding circuit and high speed contacts, a switch for controlling asection of said resistance, an actuating circuit for said switch including said high. speed contacts, a seli=ho1ding circuit for said switch, and means, responsive to operation of said controller to reverse said field winding clr cait, ior interrupting said self-holding circuit.

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