US2864973A - Control circuit - Google Patents

Description

CONTROL CRQUIT Charles L. Scott, Perms, Ohio, assignor to Westinghouse Electric Corporation, East liittsburgh, Pa, a corporation of Pennsylvania Application September 29, 1955, Serial No. 537,329

2 Claims. (Cl. 315116) My invention relates to a circuit for controlling the operation of a gaseous discharge device and, more particularly, to a circuit for automatically controlling the operation of a gaseous discharge device of the type requiring a number of operations to be performed to properly place the device in operation.

As is well known in operating certain discharge devices, such as a short-arc mercury lamp, it is desirable to heat the lamp prior to applying the starting voltage to the lamp in order to decrease the voltage which is required to start the lamp. It is also well known that the voltage required for starting such devices is considerably higher than the voltage required for maintaining the discharge device in operation once the discharge is established. Heretofo-re, in applications of such devices it has been necessary to supply a manual control station having a line switch and other switches, such as a heater switch and a starting switch, which switches were required to be operated in a particular time sequence in order to insure proper starting'of the discharge device. With suchmanual control, the discharge devices frequently did not receive the proper heating prior to the application of the starting voltage which, in many instances, resulted in a shortened life of the device. As devices, such as mercury lamps are fairly expensive, such manual control circuits have been unsatisfactory.

Accordingly, one object of my invention is to provide a new and improved control circuit for a gaseous discharge device which automatically preheats the device and applies a'starting voltage to the discharge device in a predetermined timed sequence.

Anotherobject of my invention is to provide a new and improved control circuit for a gaseous discharge device comprising a heater for heating the discharge device and an'automatically energized means for applying a starting voltage to the discharge device after the discharge device has been heated for a definite time interval.

Still another object of my invention is to provide a new and improved control circuit for a gaseous discharge device which utilizes a heater for heating the discharge device, an automatically energized circuit for applying a starting voltage to the discharge device after the discharge device has been heated for a definite time interval, and another automatically energized circuit for deenergi-zing the heater circuit a definite time interval after the starting voltage'has been applied to the discharge device.

Another object of my invention is to provide a new and improved control circuit for a gaseous discharge device which utilizes a heater for heating the'discharge device, an azuomatically energized circuit for applying a starting voltage to the discharge device after the discharge device has been heated, and another automatically energized circuit for deenergizing the starting circuit a definite time interval after the "starting voltage is first applied in the event the-lamp does-not start.

A more specific object of my invention isto' provide a 2,364,973 Patented Dec. 16, 1958 ice new and improved control-circuit for a gaseous discharge device comprising a heater for heating the discharge device, an automatically energized circuit for applying a starting voltage to the discharge device after the discharge device has been heated, another automatically energized circuit for deenergizing the heater circuit a definite time interval after the starting voltage has been applied to the discharge device, and still another automatically energized circuit for deenergizing the starting circuit a definite time interval after the starting voltage has been applied in the event the lamp does not start.

These and other objects of my invention will become more apparent upon consideration of the following detailed description of a preferred embodiment thereof when taken in conjunction with the attached drawing, in which a schematic representation of a control circuit constructed in accordance with the principles of my invention is shown.

Referring to the drawing, it will be noted that a control circuit embodying the principles of my invention comprises a pair of spaced electrical supply conductors 2 and 4 which are adapted to be connected to a suitable source of electrical energy (not shown), and each of which is provided with suitable line contacts 6 of a line switch which may be operated manually or by a time clock or photoelectric device so that the energization of the conductors 2 and 4 may be automatically or manually controlled as desired. The supply source is preferably an alternating current source for reasons which will become more apparent as this description proceeds; however, if desired, my invention could equally well be utilized with other sources of electrical energy. Conductors 2 and 4 are electrically connected together by means of a suitable electrical conductor 8 having a pair of spaced contacts A-1 and a suitable heater iii electrically connected in series therein. Heater i0 is of any well known resistance type which is utilized to heat a short-arc mercury lamp 12.

Mercury lamp 12 is of well know-n construction and comprises an outer glass envelope in which are supported a pair of cathodes '14 and 15 in spaced relationship. Electrical connections to lamp 12 are made in any suitable manner such as by supporting lamp 12 in a pair of spaced lampholders 60. Lampholders 60 are of well known construction and are obviously designed for the particular lamp, such as the lamp 12, with which they are to be used. As shown, each lampholder 60 is provided with a contact62 for engaging a lamp terminal for eitherthe cathode 1 or 15, depending upon which end of lamp 12 the lampholder is placed. Lampholders 60 are also provided with terminals 64 to which the conductors 16 and 18 are secured in any suitable well known manner. The terminal 64 and the contact 62 of each lampholder 60 are electrically connected by any suitable means such as a conductor 66, so that the cathodes 14 and 15 of lamp 12 are energized when the conductors 16 and 18 areenergized. It will be noted that each of the conductors 16 and 18 is provided with a suitable ballast coil T-l connected in series therewith. As more fully described hereinafter, the secondary of a pulse transformer T-3 is also electrically connected in series in the conductor 18, be-

' tween the ballast coil T-ll therein and the cathode 15.

member engageable with the contacts A-i in order'to- 3 control the energization of heater 10. As shown contacts A-1 are normally open so that the heater is normally deenergized. In order to provide electrical energy for operating the relay A, the oppositeends of the operating coil of relay-A are connected to the supply conductors 2 and 4 by means of suitable electrical conductors and 22, respectively. Conductor 22 is also provided with a pair of spaced contacts B-l connected in series therewith. Contacts B-1 are normally bridged by the bridging member of a relay B so that the operating coil of relay A is normally connected across the supply conductors 2 and 4. The opposite ends of the operating coil of a time delay relay E are electrically connected to t conductors 20 and 4 by means of suitable electrical condoctors 24 and 26, respectively, so that the operating coil of relay E is energized at the same time the operating coil of relay A, that is, when contacts 6 of the line switch are closed.

Relay E has a pair of spaced normally open contacts E-l, which are electrically connected in series in an electrical conductor'28. Conductor 28 is electrically connected to the supply conductor 4 and one end of the operating coil of a pair of time delay relays C and D. The other end of each of the operating coils of the time delay relays C and D is connected by means of a suitable electrical conductor 30 to the supply conductor 2, Thus, it will be noted that when contacts 6 of the line switches are closed, the operating coil of relay A is energized so that the contacts A-1 are closed and the heater 10 is immediately energized. Such energization of heater 10 causes the atmosphere within lamp 12, in juxtaposition therewith, to be heated so that a lower starting voltage can be utilized to start a discharge across the cathodes 14 and 15 of the lamp 12. Simultaneously with the energization of relay A the operating coil of relay E is also energized, but, as relay E is a time delay relay, contacts E-l will not close until the prescribed time interval for operation of the relay E has elapsed. In actual practice, a time delay of about two minutes for the relay E has been found desirable so that the lamp 12 is heated for at least two minutes before any further control will occur. Upon the lapse of the two-minute interval, contacts E-1 of relay B will close and the operating coils of relays C and D are connected across the supply conductors so as to be energized.

As relays C and D are also time delay relays and have normally open spaced contacts C-1 and D4, respectively, which will not close until the prescribed time interval has elapsed, the control functions of C and D will not occur until the total time lapse of the relay E and the relays C and D have occurred. As before, a time interval of about two minutes delay for the relays C and D has been found satisfactory. As the time increments for relays C and D are the same, their contacts C-1 and D-l, respectively, will close simultaneously and, accordingly, after approximately a four-minute interval separate control functions will be initiated simultaneously which are, however, described hereinafter independently.

Referring to relay D, it will be noted that its contacts D I are electrically connected in series with a suitable electrical conductor 32, one end of which is electrically connected to the supply conductor 4, and the other end of which is electrically connected to one end of the operating coil of a time delay relay F. The other end of the operating coil of time delay relay F is electrically connected to the supply conductor 2 by means of a suitable electrical conductor 34 so that when contacts D-l close, the operating coil of relay F is energized.

Relay F is provided with a pair of spaced normally engaged contacts F-1, one of which is connected to the conductor 32 by means of a suitable electrical conductor 35, and the other of which is connected by means of a suitable electrical conductor 36 to the conductor 16 between the lamp 12 and the ballast coil T-1 therein. As shown, the primary of a starting transformer T-2 is electrically connected in series with the conductor 36. Thus, when the contacts D-1 close, line voltage is applied across the operating coil of the relay P so that relay F is energized; however, as relay F is a time delay relay, the contacts F-1 of relay F will not open until the prescribed lapse of time has occurred. During the time interval that contacts F1 and D-l are closed, a current will flow through the primary of the starting transformer T-2 which, when the conductors 2 and 4 are connected to an alternating current source of power will be an alternating current wave. It will be noted that during the period contacts F-l and D-1 are closed the primary of transformer T-2 is directly connected across the conductors 2 and 4 by means of conductors 16, 36, closed contacts F-l, conductor 35 and conductor 32 having closed cont. cts D-i. therein.

As shown, a resistance 38 and a condenser 40 are connected in series across the secondary of the transformer T-2 so that such current flow through the primary of the transformer T2 will cause the condenser 40 to become charged. Inasmuch as resistor 38 is connected in series with condenser 40, it will function to limit the current flow in the secondary of the transformer T-2. Condenser 4G, in turn, is connected by means of conductors 42 and 44 to one side of the spark gap 46 and one end of the primary of the pulse transformer T-3, respectively. The other side of the primary of pulse transformer T-3 is connected to the other side of the spark gap 46 by means of a suitable electrical conductor 48. When the charged condenser 40 reaches a voltage value equal to or slightly greater than the breakdown voltage of the spark gap 46, the spark gap 46 will break down so that the condenser 40 will discharge and cause a pulse current to flow from one side of condenser 40 through conductor 42, across spark gap 46, conductor 48, the primary of pulse transformer T-3, and conductor 44 to the other side of condenser 40. Such pulse current flow through the primary of the transformer T-3 will cause a voltage pulse to appear in the secondary of the transformer T-3 which will be superimposed upon the supply voltage to the lamp 12 as the secondary of the pulse transformer T-3 is connected in the conductor 18. In order that the phase relationship between the superimposed voltage and the supply voltage are the same, tightly coupled low reactance transformers T-2 and T-3 are utilized.

When the applied voltage across the cathodes 14 and 15 of lamp 12 is equal to or slightly greater than the breakdown voltage of the heated lamp 12, a conducting arc is struck between the cathodes 14 and 15 of the lamp 12 and the lamp 12 emits light. It will be obvious that my invention is applicable to circuits in which the normal supply voltage is insufiicient to cause break down of the lamp. As has been indicated pre-heating of the lamp decreases the voltage required for starting, and according- 1y I have provided a circuit which automatically preheats the lamp so that the voltage pulse need not be as of great a magnitude as with cold starting of the lamp. Due to the resistance characteristics of lamp 12 at the instant the lamp 12 conducts, the voltage across the starting circuit, including the primary T-2 of the starting transformor as previously described, drops below the voltage across the conductors 2 and 4, and accordingly, the spark gap 46 stops conducting as it is no longer supplied with sufficient voltage by the primary of the transformer T-2. Thus, no further high voltage pulses will be applied to the lamp 12 after it starts to conduct. However, as relay F is of the time delay type, the contacts F-l will open after the requisite time has elapsed regardless of Whether lamp 12 starts or not, so that the primary T-2 is automatically disconnected from the supply circuit. Thus, if the voltage pulses are insufiicient to cause the lamp 12 to start, the voltage pulses will automatically be discontinued so that the starting circuit will not be damaged due to continuous operation. In actual practice, a time interval of about 45 seconds has been found to be satisfactory for opening the contacts F-l.

If desired, in order to prevent the high frequency currents which are created by thestarting circuit from afiecting the source, acapacitor Cit may be connected between conductor 16 and conductor 18 by-means of a suitable electrical conductor 31. As shown, conductor 3 1 is connected to conductor 16 between the ballast coil T-l connected therein and the lamp 12, and is connected to conductor 13 between the ballast 'coil T-l therein and the secondary of transformer T3. Also, if desired, a condenser C2 may be connected in. parallel with condenser C1 to prevent condenser Cl from having any inductive effect at high frequencies. H

As has been previously indicated, the relay C is energized simultaneously with relay D. As shown, relay C is provided with a pairof spaced contacts 'C-l, one of which is electrically connected to the supply conductor 2 by means of a suitable electrical conductor 50, and the other of which is electrically connected by means of a suitable electrical conduct'or 52 to one end of the operating coil of a time delay relay B. The otherend of the operating coil of relay B is electrically connected by means of a suitable electrical conductor 54 to the other supply conductor 4. The contacts C-1 of relayC are normally open so that after the appropriate lapse of time has occurred, the contacts 0-! will close thereby energizing the operating coil of the relay B. Relay B is provided with a pair of normally closed,'spaced contacts "B-l inthe electrical conductor 22 previously described. Thus, it will be noted that after the appropriate time lapse of relay B, the contacts 3-3. will open so that the operating coil of the relay A is disconnected from the source. Upon such energization of relay B and deenergization of relay A, the contacts A-It will separate whereby the heater 10 is disconnected from the supply conductors 2 and 4. In actual practice a time delay of about two minutes for relay C and about 45 seconds for relay B is found to be satisfactory so that the operation of relays C and D will occur simultaneously after about a two minute interval, and operation of relays B and P will occur simultaneously after about a 45 second interval.

Thus, it will be noted that the heater-10 is deenergized regardless of whether the lamp 12 strikes or not. Further, although relays C and D, have the same time delay period, such equality is not necessary and may be varied as desired. It is necessary, however, that relay D have a time period so as to remain deenergized until a sufficient time has lapsed to permit the lamp 12 to become heated by heater 10. Also the same time delay periods of relays B and F are not necessary and may be varied somewhat as desired, although preferably they are the same so that all components are deenergized at thesame time.

It is to be realized that the various time delay relays B, C, D, E and F are all of well known construction and may be of any suitable type such as a thermostatic delay relay which is connectable to a 115 volt 60 cycle supply. Accordingly, it is not believed that such relays need be more particularly described. Similarly, relay A is provided with a standard 115 volt operating coil type of well known construction and need not be more particularly described. The relays, which are utilized, are obviously selected with relation to the particular source of electrical energy which is utilized; however, it should be noted that my invention can be used with a source of energy over a wide range of supply voltages and need not be restricted to the illustrative example of 115 volts, 60-cycle source.

In a similar manner, the ballast coils T-l and the trans- I formers T2 and T-3 are Well known in the art and their construction need not be further described. Spark gap as, condenser 40, resistance 38, and heater 10 are also well known components and need not be further described. In actual practice it has been found desirable to provide a spark gap having a gap setting of about .036 inch, a condenser 40 having a rating of about .01 microfarad, 8000 volts, and a resistance 38 having a rating of about 200 watts, 7500 ohms, while the heater 10 has a value of about 900 watts. Lamp 12 may be a well known standbefore impressing the starting voltage.

farad, 2000 volt and a 500 micro-microfarad 20,000 volt condenser has been-satisfactory for condensers -C-'-1 and C2 respectively. Obviously, 'relaysA, B, C, -D,-E and F will be deenergized when line switch contacts 6 are opened so that all their respective contacts return to their normalv position whereby a circuit can onceagain be utilized-as described.

Thus, it will be noted thatl have provided an operating circuit for short-arc mercury lamps which automatically upon the closing of the contacts 6 energizes the circuit so that thelamp heater 10 is immediately energized and heats 'the lamp 12 a predetermined time before any further control takes place. Thereafter the heater continues to heat the-lamp l2 and a high voltage pulse is applied which is sufficient to start the lamp. Theheater it is later disconnected regardless of whether the lamp strikes or not after a certaintime interval has lapsed.

Similarly, the high voltage pulse is discontinued immcdiately if the lamp 12 strikes, or after a prescribed time limit if the lamp 12 does not strike. Furthergalthough this description has been withreference to short-arc mercury lamps it-is to be :realized that the described control is only illustrative and that, if desired, it could be employed with other types of gaseous discharge devices of either high or low pressure.

With the time periods for the relays as described above it will be noted that heater 10 is energized for a period of approximately four minutes, that is, the combined periods of relay E and relay C, before the high voltage pulse is applied to the lamp 12. Heater 10 is thereafter heated for an additional forty-five seconds, that is, until the operation of relay B, so that the lamp 12 remains in its heated condition as long as high voltage starting pulses are applied. Similarly, the starting circuit is not energized until four minutes after lamp heating has started, that is, the combined periods of relay E and relay D, to insure that the lamp 5 is properly heated After a fortyfive second period, that is, until the operation of relay F, the starting circuit is deenergized in the event the lamp 12 has not started in order to prevent damage to the starting circuit. Although the various relays have been described as separate relays it is believed obvious that if desired the functions of the various relays could be accomplished by multiple contact relays such as by utilizing a single relay for the relays C and D and a single relay for the relays B and F.

Having described a preferred embodiment of my invention in accordance with the patent statutes, it is desired that the invention be not limited to the particular structure described herein, as it will be readily apparent to persons skilled in the art that various changes and modifications may be made in this particular construction without departing from the broad spirit and scope of this invention. Accordingly, it is desired that the invention be given a broad scope, and that it be limited only as required by the prior art.

I claim as my invention:

1. A starting arrangement for electric discharge devices comprising, supporting means for a discharge device and having terminals, supply conductors connected to switch means for connecting said supply conductors to a source of electrical energy, means connecting said terminals to the supply conductors, heating means adjacent said supporting means for heating a discharge device supported thereby, circuit means connecting said heating means to said supply conductors, a quick acting heater energizing relay having normally open contacts in the circuit means for the heating means and having operating means connected to said supply conductors, means for producing a high voltage pulse connected to said means connecting said terminals to said supply conductors, time delay relay means having operating means also connected to said supply conductors and having contacts in a circuit connecting said pulse producing means to said supply conductors, and additional time delay relay means having operating means connected to said supply conductors by the contacts of the first-mentioned time delay relay means and having normally closed contacts in the connection of the operating means for said heater energizing relay to said supply conductors, and in the connection of said pulse producing means to said supply conductors so that when said supply conductors are energized said heating means will be energized for a predetermined time and then said pulse producing means will he energized for a predetermined time at the end of which the heating and pulse producing means will be deenergized.

2. A starting arrangement for electric discharge devices comprising supporting means for a discharge device and having terminals, supply conductors connected to switch means for connecting said supply conductors to a source of electrical energy, means connecting said terminals to the supply conductors, heating means adjacent said supporting means for heating a discharge device supported thereby, circuit means connecting said heating means to said supply conductors, a quick acting heater energizing relay having normally open contacts in the circuit means for the heating means and having 8 operating means connected to said supply conductors, means for producing a high voltage pulse connected to saidmeans connecting said terminals to said supply conductors, time delay relay means having operating means also connected to said supply conductors and connection of the operating means for said heater energizing relay to said supply conductors, and in the connection of said pulse producing means to said supply conductors so that when said supply conductors are energized said heating means will be energized for a predetermined time and then said pulse producing means 'will be energized for a predetermined time at the end of which the heating and pulse producing means will be deenergized.

References Cited in the file of this patent UNITED STATES PATENTS 721,387 Potter Feb. 24, 1903 2,043,023 Westendorp June 2, 1936 Francis Dec. 21, 1948

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