US3536969A

US3536969A - Elevator motor control

Info

Publication number: US3536969A
Application number: US717723A
Authority: US
Inventors: Ilmar Ervin Laas
Original assignee: Otis Elevator Co
Current assignee: Otis Elevator Co
Priority date: 1968-04-01
Filing date: 1968-04-01
Publication date: 1970-10-27
Anticipated expiration: 1987-10-27
Also published as: FR2005317A1; CA930084A; GB1216978A; DE1916061A1; CH491039A

Description

United States Patent US. Cl. 318158 9 Claims ABSTRACT OF THE DISCLOSURE A control for a generator of a motor generator drive for an elevator car including car operating means connected to a power supply and a field winding of the generator for controlling the excitation of said generator field winding to cause up and down movement of the elevator car, a resistor having portions connected in series to said generator field winding, a plurality of contacts of accelerating switches respectively connected in parallel to said series of resistor portions for shorting out said resistor portions one at a time to increase the excitation of said generator field winding for changing the speed of the elevator car, switch actuating means having a circuit connected to said accelerating switches for actuating said accelerating switches one at a time, and timing means having a circuit connected to said switch actuating means for regulating said switch actuating means.

The present invention relates to an elevator control and particularly to an elevator control, which controls the generator of a motor-generator drive for an elevator.

A conventional control of the generator of the motorgenerator drive for an elevator has a resistor, which is connected in series with the generator field winding. Portions of the resistor are connected in parallel with contacts of individual accelerating switches, which operate to short out respective portions of the resistor to increase the excitation of the generator field in order to change the elevator speed. These accelerating switches are conventionally controlled by individual condenser timed circuits. Each of these circuits is adjusted to provide a predetermined time interval which regulates the timing sequence.

In accordance with one embodiment of the present invention, a single timing circuit is provided in place of the plurality of individual condenser-timed circuits. With this single circuit, the number of adjustments to be made for adjusting the time intervals of the switches is minimized. Moreover, changes in the time intervals of the switches caused by variations in the line voltages are also minimized.

Accordingly, it is one object to provide a control for the generator of a motor-generator drive for an elevator.

It is another object to provide an accelerating timing control for the generator of a motor-generator drive for an elevator.

Other objects will become apparent upon reading the following description and accompanying drawings, where- FIG. 1 is a schematic diagram of an elevator system; and

FIGS. 2 and 3 are schematic wiring diagrams of a control for an elevator system embodying features of the present invention.

Referring to FIG. 1, there is shown an elevator car having a motor 11 with a generator 12 of a motorgenerator set. Elevator car 10 is rated and lowered by one or more hoist ropes 13, which pass over a traction sheave 14 and which are fastened at one end to the car 10 and at the other end to a suitable counterweight 15.

Motor 11, which is a direct current hoisting motor, is mechanically connected to sheave 14. The motor field winding MP is connected to a source of direct current, while the armature is connected to he armature of the generator 12. Generator 12, which is a direct current generator, is driven by a suitable prime mover (not shown) and is provided with a shunt field winding GF.

Referring now to FIGS. 2 and 3, the electromagnetic switches employed in the circuits are illustrated in a deenergized condition. As shown in FIG. 2, manual switch 16 is a simplified representation of the major portion of a conventional elevator car operating system. The coil of an up direction relay U is connected between one terminal of manual switch 16 and the conductor HL1. The coil of a down direction relay D is connected between the other terminal of manual switch 16 and the direction current conductor HL1, and manual switch 16 is connected between the direct current conductor L1 and the coils of relays U and D.

As shown in FIG. 2, a resistor GFR is connected to conductor L1, and a plurality of making contacts 1E3, 2E3, 3E3, 4E3 are connected in parallel with respective portions of resistor GFR. A pair of making contacts U1 and D1 are connected in series with each other and are connected between resistor GFR and conductor HL1 and a second pair of making contacts D2 and U2 are also connected in series with each other and are together connected in parallel with making contacts U1 and D1. The generator field-winding GF is connected to a terminal between contacts U1 and D1, and a terminal between contacts D2 and U2.

Referring to FIG. 3, there is shown in a plurality of coils of accelerating

switches

1E, 2E, 3E, 4E. These switches have a numerical designation indicating the sequence of operation of the switches. A plurality of making contacts 1E1, 2E1, 3E1, 4E1, are respectively connected in series between the coils of their

respective switches

1B, 2B, 3E, 4E and conductor HL1. As explained hereafter, each switch becomes self-held by operation of its respective making contacts.

A plurality of mechanically operated decelerating switches SLS4, SLS3, SLS2, SLS1, are respectively connected in series with the coils of

switches

1E, 2E, 3E, 4E, and each decelerating switch is connected to direct current conductor L2 and in series with its switch. The decelerating switches are actuated in sequence by well known conventional mechanical apparatus (not shown), as the car approaches each landing at which it is to stop.

In the circuit of the coil of switch 1E, a pair of mak ing contacts U3 and D3 of the up and down direction relays U and D respectively are connected in parallel with each other, and each of said contacts U3 and D3 is connected between decelerating switch SLS4 and the coil of timing switch 1E. Making contacts 1E2 are connected between decelerating switch SLS3 and the coil of accelerating switch 2E, and making contacts 2E2 are connected between decelerating switch SLS2 and the coil of accelerating switch 3E. Making contacts 3E2 are connected between decelerating switch SLS1 and the coil of accelerating switch 4B.

As shown at the bottom of FIG. 3, the coils of the odd-numbered accelerating switches, i.e. the first and third accelerating switches 1E and 313 are connected in series with a resistor R7, which is connected to the anode A1 of a silicon controlled rectifier SCR1. A pair of diodes D4, D5 are respectively connected between the coils of the first and third accelerating switches 1E and 3E and resistor R7, with each diode being connected in series between the coil of its respective accelerating switch and resistor R7. The cathode K1 of the silicon controlled rectifier SCR1 is connected to conductor HL1; and the gate G1 of the silicon controlled 3 rectifier SCR1 is connected in series with a resistor R5. A diode D1 is connected in series between resistor R and the base B1 of a unijunction transistor T1. A resistor R11 and a condenserC4 are connected in parallel between the gate G1 and the cathod K1 of the silicon controlled rectifier SCR1.

I The coils of the even-numbered accelerating switches, i.e. the second and fourth accelerating switches 2E and 4B are connected in series with a resistor R10, which is connected'to the anode A2 of a second silicon controlled rectifier SCR2. A pair of diodes D6, D7 are respectively connected between the coils of the second and

fourth accelerating switches

2E and 4E and resistor R10, with each diode being connected in series between the coil of its respective accelerating switch and resistor R10. The cathode K2 of the silicon controlled rectifier SCR2 is connected to conductor HL1; and the gate G2 of the silicon controlled rectifier SCR2 is connected in series with a condenser C2. A diode D2 is connected in series between condenser C2 and base B1 of unijunction transistor T1; and a resistor R6 is connected between anode A1 of the silicon controlled rectifier SCR1 and the terminal of condenser C2, which is connected to diode D2. A resistor R12 and a condenser C5 are connected in parallel between gate G2 and cathode K2 of silicon controlled rectifier SCR2.

A coupling condenser C3 is connected between anode A1 of silicon controlled rectifier SCR1 and anode A2 of silicon controlled rectifier SCR2. Each of the resistors R8, R9 is connected from the anode of its respective rectifier SCR1, SCR2, to conductor L2. A diode D3 is connected to terminal between resistors R8 and R9 and is connected by way of breaking contacts 4E2, contacts U3 or D3 and switch SLS4 to conductor L2.

A resistor R1, a potentiometer IEP, a potentiometer S, a protective resistor R2 and a condenser C1 are connected in that order in series between conductors L2 and HL1 through contacts 4E2, contacts U3 or D3 and switch SLS4. A Zener diode Z1 is connected between conductor HL1 and the junction point of resistor R1 and potentiometer lEP. A resistor R3 is connected to base B2 of the unijunction transistor T1 from the junction point of resistor R1 and potentiometer lEP. Making contacts 1E4 are connected between the terminals of potentiometer 1EP. An output resistor R4 is connected between base B1 of the unijunction transistor T1 and conductor HL1. Emitter E of the unijunction transistor T1 is connected to the terminal of condenser C1, which is connected to protective resistor R2.

The circuits at the bottom of FIG. 3 comprise two electronic switches, which control the accelerating switches 1B, 2B, 3B and 4E. While only four accelerating switches are shown in FIG. 3 for convenience of illustration, it is apparent that a larger number of accelerating switches can be similarly controlled by the two electronic switches. The accelerating switches are alternately connected to the electronic switches with the oddnumbered accelerating switches (1B, 3B) being connected to the first electronic switch and the even-numbered accelerating switches (2E, 4E) being connected to the second electronic switch as explained hereafter.

For operation, a power supply of a suitable direct current voltage is supplied between conductor L2 and conductor HL1. Resistor R1 and Zener diode Z1 provide a regulated voltage supply of a suitable direct current voltage to a relaxation oscillator circuit, which includes potentiometer lEP, potentiometer S, protective resistor R2, condenser C1, resistor R3, unijunction transistor T1 and output resistor R4. The regulated voltage arrangement allows the timing intervals for switches 1B, 2B, 3B and 4E to be independent of the power supply voltage fluctuations and insures the stability of the oscillator frequency. The purpose of said relaxation oscillator circult is to furnish the proper time spaces between the triggering signals to the gates of the silicon controlled rectifiers SCR1 and SCR2.

In operation, assuming the distance-controlling switches SLS1-4 are closed and up direction has been established to close contacts U3, the regulatedvoltage appears at the terminal of resistor R1, and charges condenser C1 through otentiometers IE1 and S and protective resistor R2. As the voltage across condenser C1 rises and reaches a predetermined level, unijunction transistor T1 switches to its conductive state providing a low resistance path between its emitter E and its base B1. This permits condenser C1 to dischargerapidly through output resistor R4 and a positive pulse appearsacross this resistor. When condenser C1 discharges below a predetermined value, unijunction transistor T1 turns off. Condenser C1 thereby starts to charge again and the process repeats as long'as power is applied to the resistor R1 and Zener diode Z1. The frequency of the repeat cycle is determined by the resistance and capacitance values of potentiom e ters IEP and S and condenser C1. Making contacts 1E4 are provided to short out potentiometer lEP before the second time interval, which is after the first pulse so that the first time interval is measured by potentiometers 1E? and S and the second and succeeding time intervals are measured by potentiometer S only. This makes, the first time interval slightly longer than succeeding ones.

With U3 closed in this way, the circuit of L2, SLS4, U3, 4E2, R1, Z1, to HL1 is closed. In addition, the circuit of L2, SLS4, U3, 4E2, R1, lEP, S,- R2, C1 to HL1 is closed. Furthermore, the circuits of L2, SLS4, U3, 4E2, R1, R3, B2, B1, R4 to HL1 is closed. Because these circuits are closed, the unijunction oscillator is operative to send pulses at spaced time intervals to the SCR units.

When the first pulse appears from condenser C1, it is directed through diode D1 and resistor R5 to gate G1 of silicon controlled rectifier SCR1. This causes silicon controlled rectifier SCR1 to become conductive. When the first pulse appears from condenser C1, diode D2 cannot con duct against the high potential at the junction point between diode D2 and condenser C2 so that the pulse is directed only to gate G1 of rectifier SCR1 by way of diode D1 and resistor R5. When rectifier SCR1 goes into conduction, the high potential at the junction point of diode D2 and condenser C2 drops and its blocking action ceases so that the second pulse triggers rectifier SCR2.

Capacitor C2 is initially charged in the manner as indicated hereafter. With U3 closed, the circuit of L2, SL'S4, U3, 4E2, D3, R8, R6, C2, R12 to HL1 is closed. This circuit through C2 has a time constant which is much smaller than the time interval of the circuit through T1, D1 and SCR1 so that capacitor C2 is initially charged before the first pulse occurs. When C2 is charged, the R6 side of C2 has about the same voltage as the supply voltage at L2, such as volts. Thus, after the first time interval, the first pulse passes from C1 through D1 and R5 to the gate G1 of SCR1, but the first pulse does not go to SCR2 be cause it is blocked by C2 which is charged, so that the first pulse actuates SCR1.

The gating action of D2, R6 and C2 control the alternate triggering of SCR1 and SCR2. If SCR1 is off, it will be turned on by the first trigger pulse, but SCR2 will not be turned on since D2 is reverse biased by a high voltage equal to the supply voltage, such as about 120 volts, and hence blocks the trigger pulse so that it cannot reach the gate of SCR2. If SCR1 is on, however, then D2 will be foward biased by a low voltage, such as by less than one volt, so that the trigger pulse will be able to trigger SCR2, which then turns off SCR1 through the action of commutating capacitor C3. Thus, at start-up, when both SCR1 and SCR2 are off, the pulse starts SCR1. Later, when only SCR1 is on, the second pulse starts SCR2, which shuts off SCR1. Thereafter, when only SCR2 is on, the third pulse SCR1, which shuts off SCR2. In this way, SCR1 and are triggered alternatel b the s aced l the UJT oscillator. y y p p 868 from The circuit, which includes silicon controlled rectifiers SCR1 and SCR2, coupling condenser C3, resistors R7,

R10, R11, R12, condensers C4, C5, forms a solid state multivibrator, which provides an alternate switching action for the coils of accelerating

switches

1E, 2E, 3E and 4E. When either of the silicon controlled rectifiers SCR1 .or SCR2 is not conducting, the rectifier acts as an open circuit. When either of the silicon controlled rectifiers SCR1 or SCR2 is triggered by a signal to its gate, it switches into conduction and continues to conduct until the voltage of its anode is decreased below a predetermined level. Assuming the distance-controlling switches SL-S1-4 are closed and up direction has been established to close contacts U3, when the first pulse appears from condenser C1, the silicon controlled rectifier SCR1 is triggered into conduction and the potential of its anode A1 drops to a low level whereby a circuit is completed to conductor HL1 from conductor L2 through switch SLS4, contacts U3, the coil of acceleration switch 1E, diode D4, resistor R7 and the anode cathode circuit of silicon controlled rectifier SCR1. This energizes the coil of switch 1E and the switch closes contacts 1E1 to complete the self-holding circuit for its coil. Although the closing of contacts 1E1 short circuits the connection from the coil of switch 1E through rectifier SCR1, the rectifier continues to conduct current through the circuit including L2, SLS4, U3, 4E2, D3, R8, SCR1, HL1 and the circuit including resistor R9 and condenser C3. This causes coupling condenser C3 to become fully charged through the circuit including contacts 4E2, diode D3, resistor R9, and the anode cathode of rectifier SCR1.

When the second pulse comes from condenser C1, it triggers rectifier SCR2, and the potential of anode A2 decreases to the value of the low voltage drop of rectifier SCR2. Since the anode A1 of rectifier SCR1 must instantaneously remain at a much lower voltage than the anode A2 of rectifier SCR2 owing to the charge on condenser C3, rectifier SCRI switches back to its non-conductive state. Condenser C3 then charges to an opposite polarity through the circuit including contacts 4E2, diode D3, resistor R8 and the anode cathode of rectifier SCR2.

On the third pulse, rectifier SCR1 again triggers, and the charge on condenser C3 drives rectifier SCR2 into non-conduction. In this Way, rectifier SCR1 triggers on the odd-numbered pulses and rectifier SCR2 triggers on the even-numbered pulses.

Diodes D4, D and diodes D6, D7, each is operative to isolate the remaining coil in its group when one coil in its group is energized. For example, when coil 1B is energized, diode D4 isolates the circuit of coil 3E from the circuit of coil 1B. In addition, resistor R7 coacts with diodes D4, D5, and resistor R10 coacts with diodes D6, D7, to allow a voltage change at its associated anode portion A1 or A2 while the terminal of the coil of its associated accelerating switch is at ground voltage.

The circuit through condenser C4 and resistor R11 and the circuit through condenser C5 and resistor R12 act to dampen stray pulses and to minimize accidental triggering of rectifiers SCR1 and SCR2.

Thus, the manner in which the lower portion of the circuit of FIG. 3 operates after relay 1E holding contacts 1E1 are closed can be briefly stated in the following. Because U3 is closed, the oscillator circuit, including L2, SLS4, U3, 4E2, R1, Z1 and HL1 remains closed, and also the circuit including L2, SLS4, U3, 4E2, R1, 1EP, S, R2, C1 and HL1 remains closed, and also the circuit including L2, SLS4, U3, 4E2, R1, R3, B2, B1, R4 and HL1 remains closed, so that capacitor C1 of the unijunction oscillator continues to alternately trigger SCR1 and SCR2 until either U3 or 4E2 or SLSl-SLS4 is opened. After relay 1E holding contacts 1E1 are closed by SCR1, the circuit of L2, SLS4, U3, 4E2, D3, R8, SCR1 to HL1 remains closed until SCR1 is shut off by SCR2. After relay 2E holding contacts 2E1 are closed by SCR2, the circuit of L2, SLS4, U3, 4E2, D3, R9, SCR2 to HL1 remains closed until SCR2 is shut off by SCR1. Thereafter, holding contacts 3E1 and 4E1 are closed in sequence by a repeat cycle in the operation of SCR1 and SCR2.

The operation of the elevator motor control is now considered. The portion of car operating system represented by manual switch 16 selects the direction of travel of elevator car 10. If up direction is selected, a circuit is completed from conductor L1 through the coil of relay U to conductor HL1. Energization of the coil of relay closes contacts U1 and U2 thereby completing a circuit from conductor L1 through resistor GFR and generator field winding GF. Energization of winding GF causes current to fiow through motor 11 so that upward movement of elevator 10 is initiated. If down direction were selected instead of up direction, a circuit would instead be completed through the coil of relay D, which would close contacts D1 and D2 thereby completing a circuit through winding GF. This causes current to flow through motor 11 in the opposite direction so that drownward movement of elevator car 10 would be initiated. The control of the speed and acceleration of motor 11 is accomplished by shorting out portions of resistor GFR by engaging respective contacts 1E3, 2E3, 3E3 and 4E3.

Through the operation of the foregoing multivibrator, when the first pulse triggers rectifier SCR1, the coil of switch IE is energized, closing self-holding contacts 1E1, contacts 1E2 in preparation for the next pulse and contacts 1E3 to short out the first portion of resistor GFR. When the second pulse triggers rectifier SCR2, the coil of switch 2B is energized, closing self-holding contacts 2E1, contacts 2E2 in preparation for the next pulse and contacts 2E3 to short out the second portion of resistor GFR.

Switches

3E and 4E act in a similar fashion on the third and fourth pulses. When switch 4E operates, it opens contacts 4E2 and disconnects the multivibrator circuit from conductor L2.

From the foregoing, it will be understood that this circuit provides stable and constant time intervals, which do not vary with the supply voltage and which accurately control the acceleration switches. There is provided a circuit, which operates on the principle of a solid state multivibrator wherein its conduction is controlled by variable RC networks and its switching is used to energize the accelerating switches.

While the present invention has been described in a preferred embodiment, it will be obvious to those skilled in the art that various modifications can be made therein within the scope of the invention. It is intended that the appended claims cover all such modifications.

What is claimed is:

1. An elevator control comprising:

an elevator car for serving a plurality of floors,

a direct current hoisting motor for said car,

a direct current generator for supplying current to said motor at variable voltage,

said generator having a field winding,

a source of direct current for said field winding,

a circuit connecting said field winding to said source,

a resistor in said circuit connecting said field winding to said source,

a plurality of accelerating switches having contacts connected in parallel with portions of said resistor,

a multivibrator connected across a supply of voltage and in circuit with said accelerating switches causing sequential actuation of said accelerating switches, said multivibrator comprising first and second alternately operable portions, each multivibrator portion adapted to alternately actuate a respective group of said accelerating switches and to selectively actuate each switch in the group according to said sequence, and

timing means in circuit with said multivibrator for regulating the operation of said multivibrator.

2. The control in claim 1, in which said accelerating switches include first and second groups of self-holding switches connected in parallel across said voltage supply, each said accelerating switch having self-holding contacts in series connection therewith, and in which said multivibrator portions respectively have first and second electronic switches respectively in circuit with said groups for alternately actuating said groups, and in which said timing means comprises a single timing portion in circuit with said electronic switches for regulating the operation of both said switches, said timing portion having pulse generating means adapted to alternately actuate said electronic switches at selected time intervals.

3. The control in claim 2, in which said first and second electronic switches are controlled rectifiers having respective anode cathode portions in circuit with said first and second groups of accelerating switches and having respective gate portions for control thereof, said anode portions of the two rectifiers having a capacitive interconnection therebetween, and in which said pulse generating means is in circuit with said gate portions for feeding regulating pulses thereto and is in circuit with voltage regulating means to minimize variations in the pulses caused by fluctuations in said voltage supply.

4. The control in claim 3, in which said pulse regulating means includes a resistance-capacitance timing circuit connected across said voltage supply and connected to said voltage regulating means and includes a unijunction transistor connected across said voltage supply and connected to said timing circuit to be rendered conductive when the output voltage from said timing circuit reaches a predetermined level, and in which the gate element of said first rectifier is connected to said unijunction transistor, the gate element of said second rectifier and the unijunction transistor have a capacitive interconnection therebetween, and the anode portion of said first rectifier is connected to said capacitive interconnection.

5. The control in claim 4, in which each said accelerating switch except the first-to-be-operated switch is connected in series with sequencing contacts, said contacts being actuated by the next previously-actuated switch for controlling the sequential actuation of the accelerating switches.

6. The control in claim 5, in which the coil of each accelerating switch and the anode portion of the associated electronic switch connecting thereto have a unidirectional current-conducting isolating element in series connection therebetween for isolating electrically the remaining coils of its group of accelerating switches from said coil and its self-holding contacts.

7. The control in claim 6, in which the coil of each said accelerating switch and the anode portion of the associated electronic switch connecting thereto have a resistance element in series connection therewith and with said unidirectional current conducting element.

8. The control in claim 4, in which one of said accelerating switches has timing contacts arranged so that its actuation is effective to change the time period of the unijunction transistor and thus the time separating successive impulses from said common unijunction transistor and the conduction periods of said first and second rectifiers.

9. The control in claim 8, in which the last-operated switch of said accelerating switches has breaking contacts arranged so that the actuation of said breaking contacts is effective to disconnect said voltage supply from said timing circuit and unijunction transistor and first and second rectifiers.

References Cited UNITED STATES PATENTS 3,231,809 1/1966 Greer 31842l 3,250,972 5/1966 Morris 318141 3,341,759 9/1967 Torri 323-97 3,390,318 6/1968 Gilbert 32396 OTHER REFERENCES General Electric SCR Manual, third edition, publication dated, Mar. 23, 1964, pp. 114-115.

ORIS L. RADER, Primary Examiner K. L. CROSSON, Assistant Examiner US. Cl. X.R. 31 8-422