US1976614A

US1976614A - Plugging and accelerating control

Info

Publication number: US1976614A
Application number: US629645A
Authority: US
Inventors: Henry D James
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1932-08-20
Filing date: 1932-08-20
Publication date: 1934-10-09
Anticipated expiration: 1951-10-09

Description

Oct. 9, 1934. H. D. JAMES 1,976,614

PLUGGING AND ACCELERATING CONTROL Filed Aug. 20, 1952 2 Sheets-Sheet 1 Fig.1.

2.3v 1/5 r q: a:

WITNESSES: INVENTOR Henry D. James.

' BY fwm ATTORNEY Oct. 9, 1934. H. D. JAMES 1,976,614

PLUGGING AND'A CCELERATING CONTROL Filed Aug. 20, 1952 2 Sheets-Sheet 2 Fig. 2.

WITNESSES: INVENTOR 7 v Henry D. James.

ATTORNEY Patented Oct. 9, I934 UNITED STATES PATENT OFFICE PLUGGING 4ND ACCELERATING CONTROL vania Application August 20, 1932, Serial No. 629,645

7 Claims.

This invention relates to control systems for electric motors which systems utilize electronic discharge devices to control the operation of the motors.

One object of this invention is to provide for controlling the reversing and acceleration of a motor by electronic discharge devices.

Another object of this invention is to provide an electronic discharge device responsive to selected changes in the operating characteristics of an electric motor to control the starting and reversing of the motor.

A still further object of this invention is to control the discharge of a cold-cathode discharge tube in response to variations in characteristics of the armature current of a motor to control the acceleration and reversal of the motor.

Other objects and advantages will become more apparent from a study of the following specification, when considered in conjunction with the accompanying drawings, in which:

Figure 1 designates a system of control particularly useful as a plugging control system controlling the operation of a reciprocating motor;

and

Fig. 2 represents a system of control for accelerating a direct current motor in a substantially predetermined interval of time by the use of a cold-cathode tube.

Referring more particularly to Fig. 1, reference character 1 represents a direct current motor, the operations of which are to be controlled, whereas reference characters 2 and 3 designate the buses for supplying the direct current energy to the motor 1. The motor is provided with a plurality of reversing switches-4 and 5, and 6 and 7,

respectively. To prevent damage to the motor during starting, the accelerating resistor 8 is provided. This resistor has one section 9 thereof, designated the plugging resistor, of a relatively high resistance value.

A cold-cathode tube 10 is provided for controlling the shunting operation of the plugging contactor 11 in such manner that thiscontactor is never closed during the plugging operation before the motor has substantially come, to. rest after having operated in a given direction. 1

One of the chief advantages of a cold-cathode tube is that the starting operation or the reversing operation, as the case may be, is not impaired by the delay caused by the belated operation of electromagnetic devices or the time delay of a thermionic device-requiring the heating of a.

filament. A cold-cathode tube properly adjusted breaks down at exactly the time desired and thus does not function after an undetermined relatively long time constant as do hot-cathode devices.

To accomplish this novel and advantageous feature, the cold-cathode tube 10 is provided with a resistor 12 which resistor is interconnected with the accelerating resistor sections 13 and 14' of the armature resistor 8 by the

conductors

15 and 16. The grid 17 of the cold-cathode tube 10 is so positioned with reference to the

connecting points

18 and 19 of the

conductors

15 and 16, respectively, that a variation of current in the

conductors

15 and 16 of a predetermined amount will cause the cathode tube 10 to be deenergized, i. e., cease its discharging operation from the plate 20 to the cathode 21.

A more complete understanding of the novel features of this invention can best be had from a study of the sequence of. operation of the elements constituting the plugging controller.

Assuming that conductors or buses 2 and 3 are suitably energized and it is desired to start the operation of the motor 1 to operate the machine connected thereto, which, for this particular ap-'- plication, usually constitutes a reciprocating device. To start the operation, the attendant opcrates the push button starting switch 22 thereby establishing a circuit from the conductor 2 through stop switch 23, starting switch 22, and actuating coil 24 of the line contactor 25 to the energized conductor 3. The operation of the line contactor 25 closes the upper auxiliary contact members 26 to establish a holding circuit for the actuating coil 24, and causes a closing of the lower auxiliary contact members 27 to eifect the energization-of the control relay 28. The circuit for the control relay may be traced from the battery 29 through the lower auxiliary contact members 2'7 of contactor 25, actuating coil 30 of the control relay 28, resistor 12, and resistor 31, back to the battery.

It will be noted that the plate 20 of the tube 10 is connected to the positive terminal of the battery and that the grid 17 is connected at point 32, which may be varied, to the resistor 12. A potential-of a given value is therefore impressed across the gap between the plate 20 and the grid 17, and the tube breaks down causing a current to flow through the tube and through the resistor 31. This increased current immediately causes the operation of the control relay 28 to close its contact members.

In the arrangement shown, the coil 30 is sufllciently energized to actuate the control relay 28 by reason of the repeated discharges of the condenser 33. The condenser 33 coacts with the discharge in the tube, causing an oscillatory current to flow inthenetwork including the tube 10 and the condenser 33, and, hence, producing a variation in polarity of the potentials impressed upon the electrodes of the tube. riation in polarity of the potentials, the discharge in the tube is interrupted when the grid 17 is re- 'verted to its-original electrical condition, after current to flow in coil 30 to operate the control relay.

The closing of the contact members of the control relay 28 does not effect the operation of any of the contactors ll, 34, or unless the controller 36 has first been actuated to effect an operation of the motor 1 in the desired direction.

When the

controller segments

37 and 38,v are moved towards the left, the forward direction, circuits are established for the actuating coils of the

directional contactors

4 and 5. These circuits may be traced from the energized conductor 2 through actuating coil 39 of directional contactor 4 to'controller segment 37 and from energized conductor 2 through actuating coil 40 of directional contactor 5 to the controller segment 37 from whence the circuits are completed through conductor 41 to the negatively energized conductor 3.

The operation of the controller as first specified also establishes a circuit from the energized conductor 2through conductor 42, actuating coil 43 of the plugging contactor 11, the contact members of the control relay 28 and conductor 44 to the negatively energized controller segment 37.

The line contactor being closed, as heretofore explained; a circuit is established from the 0011-;

ductor 2 through directional contactor 4, the armature 45 of the motor 1, directional contactor 5,.

conductor 46, series field winding 47 of the motor 1, accelerating

resistor sections

13 and 14 and the pluggingresistor section 9 and contact members of line contactor 25. to the negatively energized conductor 3. During the normal acceleration of the motor, the plugging contactor 11 will, of course, operate immediately so that the resistor 9 remains in the armature circuit but a very short interval of time. However, the operation of the plugging contactor causes the closing of the auxiliary contact members 51 of the plugging contactor 11 thereby establishing a circuit for the first accelerating contactor 34. This'circuit may be traced from .the energized conductor 2 through conductor 49, actuating coil 50.0f the accelerating contactor 34 and auxiliary contact member 51 of the plugging contactor 11 to the negatively energized conductor 3.,

The accelerating

contactors

34 and 35 are provided with suitable time t

devices

53 and 52, re peqtively. which prevent the closing of these immediate closing of the accelerating contactor By reason of the vaadjustment of the time limit device 53.

resistor section 14 is shunted and auxiliary concontact members after being energized for a predetermined interval of time. The closing of contact members 51 therefore does not eifect the 34, but the contactor closes only after the lapse of a definite interval of time determined by the However, when accelerating contactor 34 closes, the

tact members 54 of the accelerating contactor 34 are closed thereby establishing a circuit from conductor 49 through actuating coil 55 of acceleratlng contactor 35, auxiliary contact members 54, and conductor 56 to the negatively energized conductor 3. It will thus be noted that the motor is brought up to full operating speed within a substantially fixed short interval of time.

Assuming that the attendant operates the controller 36 in the reverse direction, 1. e., plugs the motor to close the

directional contactors

6 and 7. A mere inspection will show that this operation connects actuating coils 5'7 and 58 of directional contactors 6 and '7, respectively, to the conductor 2 and by means of controller segment 38 and conductor 41 to the negatively energized conductor 3. Closing of the directional contactors 6 and '7 connects the armature 45 of the motor to theconductors 2 and 3 in such a manner that the counter-electromotive force of the armature 45 is additive to the applied voltage. 115 It is, therefore, obvious that substantially twice the applied voltage will be impressed across

resistor sections

13 and 14, thereby counteracting the effect of the battery 29 between the

points

18 and 19 with the result that the cold-cathode tube is extinguished because the voltage across the tube is very materially reduced.

Coil 30 is thus deenergized because resistor 12 has a resistance value suflicientiy high to prevent sufllcient current to flow in coil 30 to actuate the control relay 28. Regardless of the fact that the controller is in the reverse position, coil 43 is deenergized and the plugging contactor 11 remains open. Since the

contactors

34 and 35 are interlocked with the plugging contactor,

resistor sections

13 and 14 also remain in the circuit of the armature 45.

, As the motor decelerates the counter-electromotive force decreases and when the resistance drop across resistor sections 13 and l4is substantially zero, 1. e. the motor armature ceases rotating, the bias on the grid 19 will again. be favorable to discharge of the tube 10. Flashes thus occur in rapid succession through the tube causing sufiicient current to flow through coil 30 to openate the control relay 28 which then in turn effects the operation of the plugging contactor 11. From the foregoing explanation it is obviousthat the'plugging resistor 9 remains in the circuit until the plugging operation is completed and thereafter the acceleration of the motor takes place in i the reverse direction in a predetermined manner. Referring to the modification shown in Fig. 2, wherein a cold-cathode tube 88 is utilized to control the acceleration ofthe motor 60. In this 14 modification the rise and fall of the armature current after the closing .of the line contactor and the closing of successive accelerating contactor:

is taken advantage of to accelerate a direct cur- I 86 of the tube 88 is connected at any selected position on the resistor 80 to vary the adjustment of the tube 88. This assembly of circuits may be energized from a source of direct current such as a battery 89 through conductor 82 and resistor 83.

The voltage of the battery 89 and the other constants of the circuits associated with the tube 88 are so chosen that the tube will not break down when only the positive bias provided by the battery is available. To more clearly appreciate the novel and useful features of the modification shown in Fig. 2, a sequence of operation will be given.

Assuming conductors 61 and 66 are energized and the attendant actuates the starting push button switch 63 to energize the line contactor 65 through stop switch 62, the auxiliary contact member '73 of line contactor 65 close and the line contactor 65 closes and a holding circuit for coil 64 is established through auxiliary contact members 65'. Closing of the line contactor establishes the field circuit for the motor from conductor 61 through rheostat 101, field winding 102, conductor 67, and auxiliary contact members of line contactor to the negatively energized conductor 66. An armature circuit is also established from conductor or bus 61 through the armature 103 of the motor 60, primary winding of transformer 100, resistor sections 69, '70 and 71 of accelerating resistor 68 and auxiliary contact members of line contactor 65 to the negatively energized conductor 66.

Since contact members 73 are closed a certain positive bias will be placed on grid 86 but not sufficient to cause a break down of tube 88. The rise of armature current immediately after the closing of the line contactor establishes a variable voltage at the primary 80 and secondary 81 of the respective transformer terminals of a polarity such as indicated by the full line arrows. As soon as the current change in the rising direction has attained a pre-selected value the tube 88 breaks down and thereafter passes current by rapidly recurring impulses, the condenser84 discharging at each impulse.

The motor soon accelerates and the rise in counter-electromotive force soon causes a decay of armature current with the result that the polarities of the voltages at the respective transformer terminals will be such as shown by the broken line arrows shown in Fig. 2. The bias on the grid will thus become less positive and the successive discharges of the condenser 84 through tube 88 will cease.

During the time the tube is rapidly breaking down a considerable current passes through coils '74, 76 and '78, thereby holding the accelerating contactors '75, 7'7 and '79 open. However; as soon as the tube 88 ceases to pass current, coil '74 is not strong enough to prevent coil 90, which is subject to full line voltage, from closing accelerating contactor '75. As soon as resistor 71 is shunted by the accelerating contactor '75 the armature current again rises causing the tube 88 to again break down.

Coils

74, 76 and '78 are thus again energized and coil '76 prevents coil 91, though this coil 91 be energized by full line voltage through conductor 93 and auxiliary contact members of accelerating contactor '75, from closing the accelerating contactor '77. As soon as the armature current has gone through its rise and fall the tube 88 is again extinguished and the accelerating contactor 77 closes shunting the resistor section 70.

The coils '78 and 92 of accelerating contactor 79 are similarly energized and eventually resistor 69 is shunted. The one tube 88 may thus be utilized for any number of accelerating resistors and the motor may thus be accelerated within a substantially predetermined interval of time.

Applicant is of course aware that any one skilled in the art, after having the benefit of the teachings of this invention, can readily devise other circuit arrangements than the particular arrangements herein shown. He, therefore, wishes to be limited only by the appended claims and the pertinent prior art.

I claim as my invention:

1. In a system of control for controlling the acceleration of a motor by the successive actuation of the accelerating contactors, in combination, accelerating contactors, control means for the accelerating contactors including, a battery, a cold-cathode discharge device having principal electrodes and a control electrode, a switch for connecting the principal electrodes to the battery, circuit connections for subjecting the control electrode to a voltage having a definite relation to an operating characteristic of the motor to be'controlled and a capacitor interconnected with the discharge device and adapted to control the discharge device.

2. In a system of control for electric motors, in combination, a motor, a current limiting resistor, having a plurality of sections, for the motor, means for shunting given sections of said resistor, a line contactor, a battery, a cold-cathode discharge tube having main electrodes and a control electrode, means responsive to the operation of the line contactor for connecting the main electrodes to the battery, a condenser and a resistor and transformer secondary connected in series connected in parallel with the main electrodes, circuit connections for connecting the control electrode at any selected point on said last named resistor, a primary of a transformer responsive to electrical characteristics of the motor whereby said tube is caused to start its discharge in response to certain of said electrical characteristics and to stop its discharge at certain other electrical characteristics, and means controlled by said tube to efiect the operation of said resistor shunting means in a predetermined sequence.

3. A control system for electric motors comprising, a motor, a cold-cathode tube, means for effecting the starting of the discharge of the tube in response to certain changes in the armature current of the motor, means responsive to certain other changes of the armature current to stop the discharge of the tube, and means responsive to the operations of said tube to control the starting sequence of the motor.

4. A control system for a reversing motor comprising, a motor, a line contactor, reversing switches, a reversing controller, an accelerating resistor having a plurality of sections, a plugging resistor, a cold-cathode tube having a pair of main electrodes and a control electrode, a. condenser, a control resistor, a battery, means operable by the line contactor for connecting said main electrodes, control resistor, and condenser in parallel circuit relation to said battery, circuit connections including a selected portion of said control resistor connected in parallel to selected sections of said accelerating resistor, circuit connections interconnecting said control electrode to any selected point on the control resistor intermediate the selected portion of the control re- 5. In a system 01 control for electric motors,

in combination, a motor, a current limiting resistor for the motor, means for shunting the reeration of the line contactor for connecting the main electrodes to the battery, a condenser, and

a resistor and transformer secondary connected in series, connected in parallel with the main electrodes, circuit connections for connecting the control electrode at a selected point on said last named resistor, a transformer primary winding responsive to electrical characteristics of the motor whereby said tube is caused to start its discharge in response to certain of said electrical characteristics and to stop its discharge at certain other electrical characteristics, and means controlled by'said discharge device to control the operation of said resistor shunting means.

6. A control system for a reversing. motor comprising, a motor, a line contactor, reversing switches, a reversing controller, a series resistor connected in series with the motor, a plugging resistor, a cold-cathode 'tube having a pair oi. main electrodes and a control electrode, a conresistorfcir cu it connections interconnecting said control electrode to any selected point on the control resistor intermediate the selected portion thereof, and means responsive to certain operations oi the discharge device to control the shunting oi the plugging resistor.

7. A motor control system, comprising in combination, a main source 01' direct current power, a motor, a line contactor for connecting the motor tosaid main source of direct current power, an auxiliary source of direct current power, an electronic discharge device having a pair of principal electrodes and a control electrode, means for connecting the principal electrodes to said auxiliary source of power, said control electrode being disposed to have its voltage bias controlled by an operating characteristic of the motor, means for rapidly eflecting successive discharges oi the discharge device after the closing of the line contactor, means for intermittently I interrupting said successive rapid discharges through variations of said motor operating char-- acteristicspand means responsive to said intermittent operations to eflect the acceleration of the motor in a predetermined manner.

HENRY D. JAMES.