US1694249A - Electric regulator - Google Patents

Description

Dec. 4, 1928.

F. A. BYLES ELECTRIC REGULATOR Filed June 17, 1926 Fig. i.

Fig. 2.

VOLTS AMPERES lnvencpr 1 Frank A. Byles,

His Attorneg.

Patented Dec. 4, 1928.

UNITED STATES PATENT owl- FRANK A. BYLES, 0F SCHENEC'TADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, CORPORATION OF NEW YORK.

"nmc'rmc REGULATOR.

Application filed June 17', 1926. Serial No. 116,762. I

My invention relates to electric regulators and more particularly to current regulators of the vibratory type for use in electrical 'sys-- tems in which a constant current is desired.

The invention finds particular application in the motion picture industry where are lamps, and especially. direct current are lamps, are used as the source of screen illumination. As is well known, it is particularly desirable to maintain constant current in the arc lamp circuit, since a small chan e in current causes a material change in t 'e illumination on the screen. Many motion picture houses find .it desirable to provide two projection machines so arranged that the second machine may be operated simultaneously with a machine'in operation for a short period of time in order to change from one reel of film to another without delay. .This ms'ce'ssitates operating two are lamps either in parallel or in 'series. Arrangements in which thetwo lamps are; operated in par allel during the change-over have. the disadvantage of overloading thege'nerator, if a motor generator set is used, and the newly' started arc has a tendency to draw an unequal share of current during the initial periodof adjustment. Hence, it has been found desirable to operate the arc lamps in series during the change-over.

If two projector arc ated simultaneously in series, the source of supply must be capable of furnishing a constant current over a wide range of voltage in order to operate successfully a-single arc or a plurality of series connected arcs. The well known series are generator, designed with a drooping voltage-current characteristic, approximates some of the characteristics desired, but does'not in itself secure constancy of current, in the arc lamp. circuit. Even if this drooping characteristic is exaggerated and the usual type of current regulator is used, the result .obtained is only an approximately constant current. The results heretofore obtained may be sufiiciently accurate for general illumination purposes butwhere a more rigorous current regulation is demanded, as in motion picture projectors, an absolute constancy of illumination is desired. It has been foundthat the known regulators are not sufliciently sensitive or rapid in operation to accomplish entirely satisfactor results. 4 1

- t, therefore, isan object of my invention lamps are-to be operto provide an improved current regulator capable of operating with a generator having a. wide voltage range, which is. sensitive and sulficiently rapid in operation to maintain a substantially constant currentin a series are circuit during any operating condition imposed when arcs are used alternately or when a single or a plurality of arcs are operated continuously;

.The' novel featureswhich I believe to be characteristieofmy invention are set forth with particularity in the appended claims.

The invention itself,however, both as to organization and method of operation, together with further objects and advantages thereof,

will be better understood by-reference to the following description taken in connection with the accompanying drawing in which Fig. Us a diagrammatic illustration of a system in which my invention has been embodied, and Fig. 2 is an explanatory diagram showing a suitable voltage current characteristic for the supply-generator.

In Fig. 1 a dynamo-electric machine 1 is shown diagrammatically as a direct currentgenerator. and may be driven in any conven-' ient manner, as, for example, by an alternating current motor (not shown) connected to commercial supply mains. This dy-.

thereof is. controlled by the current regulator to be described presently. Arc lamps 5 and 6 provided with suitable electrodes, are shown diagrammatically in a. series circuit with the generator 1 and are provided respectively with shortcircuiting switches 7 and 8, which provide a means for putting any desired lamp' or lamps into operation.

As shown in the. drawing, a regulator 9 is arranged to control the shunt field excitation of generator 1 so as to maintain the current constant in the arc lamp circuit. Regulator 9 comprises cooperating-contacts 10 and 11, a-core 112, and windings 13,14. and 15.

The contact 11 is arranged to be stationary and is screw-threaded to provide a means for adjusting the contact gap so that the regulator may be arranged to hold difi'erent current values. The contact 10 is arranged to be movable and is resiliently mounted in order to permit a higher contact speed than is possible with a moving contact mechanism having appreciable iinertia. Contact 10, as shown, is supported by means of a spring 16 formed of a light, thin, fiat ribbon of steel, rigidly attached at its ends to a fixed support 17 which-is secured to the core 12. Adjacent the contact 10, and approximately at the middle of the supporting spring 16, is secured a magnetic armature 18, which is arranged to cooperate with the core 12 and its operating windings 13, 14 and 15. Winding 13 is connected in series relation with the load circuit andis of low resistance and commonly constructed of a few turns of relatively large wire. lVith normal changes in current, the action of winding 18 would be entirely too sluggish to efiect the rapid correction desired. To provide a rapid vibratory movement of contact 10, winding 14 is connected in series with a resistor 19 across the shunt field winding 2 and is arranged to act accumulatively with winding13. The action of this winding, however, has a tendency to cause the regulator to hold a lower current, as the operating voltage of the generator increases. To

compensate for this tendency, I provide a winding arranged to act differentially with respect to windings 13 and let. Windlng 15 is arranged to be responsive to the voltage impressed upon the load circuit and is connected in series with a resistor 20 across the terminals of generator 1.

The cooperating contacts 10 and 11 are arranged to actuate'a relay 21, which is provided to periodically shortcircuit or insert the resistance 4; in the circuit of field winding 2. Relay 21 comprises an operating coil 22 and contacts 23 which are connected in a parallel circuit to resistance 1. A condenser 21 is connected across contacts 23 in order to prevent excessive sparking. 22 is'arranged to be responsive to the voltage impressed upon the load circuit and is connected in series with a resistor 25 across the terminals of generator 1. The main control contacts 10 and 11 of regulator 9 are so connected as to shortcircuit the relay n'iagnet winding 22 when they close. This sequence of operation means that the relay contacts and main control contacts will open and close together when in operation.

- Similarly to the conditions existent with the usual type of vibratory regulator, the resistance a is of such a magnitude that it has considerable eilect on the voltage of generator 1 and, when included in a circuit with the shunt field winding 2, reduces the voltage of the generator considerably below the de- The operating coil sired value and, when removed therefrom, allows said voltage to increase considerably above the desired value. It, therefore, the contacts 10 and 11 berapidly opened and closed, the contacts 23 will be opened and closed andthevoltage of the generator will be repeatedly varied and its valueavill depend upon the relative length of the periods during which the contacts are opened and closed. The length of these periods will depend upon the distance by which the fixed and moving contacts are separated at each vibration, and this distance will be determined by the attracting flux in the core 12..

Let it be assumed that the dynamo-electric machine is in operation with the electrodes of the respective arc lamps ant separated. For purposes of explanation, let it beassumed that the dynamo-electricmachine 1 is designed to have an open circuit voltage of say, 180 volts, which drops to approximatelyvolts, when one lam) is burning and automatically increases its voltage to approximately 120 volts, when the second are is struck. fissulne, now, thatshortcircuiting switch 8 is closed and that are lamp 5 has been put into operation and is burning with an impressed voltage of aproximately volts and a current of approximately amperes'flowing in the circuit. This point of operation may, for convenience, be considered to be atp'oint A on the voltage-ampere characteristic shown in Fig. 2. Now assume that the arc conditions change and that regulator 9has'bcen adj usted to hold 80 amperes.

If contacts 10 and 11 are in the position shown, contacts 23 will be open and the Yul.

age impressed upon the field winding 2 will be a minimum. The winding 14 of the regulator 9 will, at this instant, have a minimum energization, and, hence, the spring 16 will move contacts 10 and 11 into engagement. Upon the engagement of contacts 10 and 11, the winding 22 of relay 21 is shortcircuited so that contacts 23 will be closed to shortcircuit the resistance-4, and the voltage impressed upon the field winding 2 will there upon increase to a maximum. Upon an increase in the voltage across the shunt field winding 2, the energization ofwinding 14 will increase, whereupon the contacts 10 and 11 will be disengaged. Contacts 28 will again be opened so that the voltage impressed upon field winding 2 is reduced to a minimum. This cycle of operation is rapidly repeated and the contact 10 is rapidly vibrated by the operating winding 14. If the current in the load circuit varies, the energization of the current winding 13 will be changed to vary the mean position of the vibrating contact 10 so that the voltage of generator 1 will be varied to maintain substantially constant current in' the load circuit.

If the load circuit resistance increases, it will be necessary to increase the generator voltage in order to maintain the current constant; This means that contacts. and 11 must remain. in engagement more of the time.

However, with an increase in voltage, the

voltage impressed across the operating winding 14 will tend to maintain contacts 10 and 11 out of engagement for a longer period of time, and this would tend to 'cause a lower voltage to be generated, and hence a lower current to be held than would correspondingly be held at lower voltages. In order to compensate for thiseflect, windin 15 is ar-- ranged to operate difierentially with respect to winding 14. Since winding 15 is energized in response to the terminal voltage of generator 1, it will tend to maintain contacts 10 and 11 in engagement for a longer period of time .as the voltage increases, and hence will coun-' teract the tendency of winding 14 to regulate for. a lower current as the voltage increases. Now, if it is desirable to start the second lamp 6, its electrodes are brought together and the. shortcircuiting switch 8 is opened.

This permits the current through the first lamp to flow through the tips of the electrodes of the second lamp. The are is then struck andthe two lamps are now operating inseries and may, for convenience of explanation, be considered as operating at thepomt .B -on thevoltage-ampere characteristic shown in Fig. 2. The operation of the regulator under these conditions will be evident from the description previously given in con- .nection with the operation of one lam since the current in the load circult 1s stil maintained at the same value and coils 14 and 15 are subjectedto an increase in voltage of the sameproportion.

1 If it is now desired to change over from one lampto the other, the electrodes of the first lamp are brought together and the shortcircuiting switch closed so that the (projec- 'tion may be continued with the secon lamp.

While I have shown and described a particular embodiment of my invention and a particularly, useful application thereof, it

will'be apparent to those skilled in the art that the invention may be applied in other relations of utility and changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true splrit and scope of my invention.

' What I claim as new and desireto secure by Letters Patent of the United States, is,-

1. In combination with a enerator having ed to operate with a drooping voltage-current characteristic, of a regulator. for maintaining constant current in said load circuit comprising a wlndmg responsive to the current in said load circuit, a .winding responsive to.

the voltage of said field-1 winding and arranged to operate -accumulatively with respectto said current winding, a vibrating contact. comprising a resiliently supported contact member actuated by said windings,.

and a winding responsive to the voltage of said generator and arranged to operatedif ated by said windings, and a winding responsive totheiwoltage of said generator for Inodifying the action of said vibrating contact throughout the voltage range of said generator.

In witness whereof, I have hereunto set my hand this 16th day of June, 1926.

. FRANK A. BYLES.

a field winding and a load c1rcuit and adapt-

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