US2444408A

US2444408A - Electric gaseous discharge lamp circuit

Info

Publication number: US2444408A
Application number: US688745A
Authority: US
Inventors: Carl M Larime
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1946-08-06
Filing date: 1946-08-06
Publication date: 1948-06-29
Anticipated expiration: 1965-06-29

Description

June 29, 1948. c. M. LARIME ELECTRIC GASEOUS DISCHARGE LAMP CIRCUIT Filed Aug. 6, 1946 IN VHV TOR.

BMW,

ATTORN ET Patented June 29, 1948 ELECTRIC GASEOUS DISCHARGE LAMP CIRCUIT Carl M. Larime, Marblehead, Mass, assignor to Sylvania Electric Products Inc., Salem, Mass, a corporation of Massachusetts Application August 6, 1946, Serial No. 688,745

2 Claims.

This invention relates to electric gaseous discharge devices and more particularly to apparatus and circuits therefor.

Electric gaseous discharge devices, particularly those having filamentary electrodes. are usually operated with relays to allow pre-heatin of the electrodes to electron-emitting temperatures, or directly from high voltage transformers without any pre-heating of the electrodes. The first method necessitates an undesirable delay in starting after the initial application of voltage to the circuit and the second method places considerable electrical stress on the electrodes and in many cases. shortens their life considerably.

An object f my invention is to provide a circuit for electric gaseous discharge devices, such as fluorescent lamps in which a relay is not requlred.

Another object is to provide a fluorescent lamp circuit which does not require a relay but which is designed so as to provide for heating the electrodes to electron-emitting temperatures before a discharge is initiated across the lamp.

A further object is to provide a fluorescent lamp circuit in which a counter-voltage is supplied to cancel out a substantial amount of the electrode pre-heatlng voltage once the lamp starts.

Further objects, advantages and features will be apparent from the following specification when read in conjunction with the accompanying drawing in which:

Figure l is a schematic diagram of the circuit of my invention.

Many of the conventional fluorescent lamp circuits designed to operate from a low voltage source such as 110-120 volts usually include a relay or starter to provide for pre-heating of the electrodes to electron-emitting temperatures and a reactance coil to provide an inductive voltage surge at starting and to ballast the lamp during operation. The circuit of my invention is designed to eliminate the necessity for a relay or starter and at the same time provide an electrode pre-heating interval.

I have illustrated the circuit of my invention as it may be used with tWo 40 watt fluorescent lamps. However it will be apparent, to those skilled in the art, from the following specification that the principles on which m circuit is based may be readily applied to fluorescent lamps of other wattages and to other types of electric gaseous discharge devices without departing from the spirit of this invention. The lamps I and 2 are provided with filamentary electrodes 3 and Q and 5 and 6 respectively. These electrodes are preferably of coiled tungsten wire coated with one or more of the alkaline earth oxides.

in the circuit of my invention a transformer uch as the auto-transformer l, is connected to a 110-120 volt line 8. Two electrode heating windings B and ID are wound on the core of the transformer l and connected to electrodes 5 and 3 respectively of lamps 2 and I respectively. One end of each of these windings is connected directly to one end of each of these electrodes. The other end of each of these windings is connected to the other end of each of these electrodes through auxiliary windings H and I2 on reactance coils l3 and I4 respectively, the purpose of which will be described more fully below.

The transformer l is tapped at I5 and the windlng l6, defined by the end ll of the main transformer winding and the tapped point I5, is connected in parallel to electrodes 4 and 6 of lamps I and 2 respectively One end of winding I5 is connected to one end of electrode 4 and electrode 6. The other end of electrode 4 is connected back to the winding l6 through auxiliar winding 18 on reactance coil l4 and the other end of electrode 6 is connected back to the winding l6 through auxiliary winding l9 on reactance coil l3.

End 20 of the main transformer winding is connected through the reactance coil M to one end of the filamentary electrode 3 in lamp I, and through a condenser 2| and reactance coil II! to one end of the filamentar electrode 5 of lamp 2. A bleeder resistance 22 may be placed across condenser 2|. Thus lamp I is inductively ballasted and lamp 2 is capacitively ballasted. The condenser is preferably of such a size that it places the two lamps sufiiciently out of phase to correct the power factor and reduce the stroboscopic effect from the pair of lamps. The capacitive reactance of condenser Zl should predominate over the inductive reactance of inductance l3 at line frequency so that net reactance in series with lamp 2 at line frequency is capacitive. in the preferred case.

In operation. when the transformer l is connected to the line 8. a voltage is applied directly to the primary and is induced in windings 9. l0. and I6. As mentioned above, these three windings are connected to the filamentary electrodes 3. 4. 5 and B of the lamps l and 2. Thus these electrode are supplied with pro-heating current as soon as the transformer l is connected to the line 8. At this time there is no current through the lamp itself. 1. e. across the discharge space helween electrodes 3 and l. and 5 and B, and hence no current through the coils l3 and I4. Thus there is no voltage induced in the auxiliary windings l and IS on coil l3 and I2 and '8 on coil l4. and hence the flow of current in the electrodes 3. 4. 5 and 6 is not greatly reduced. al.- though the auxiliary windings will have a small impedance.

When the electrodes 3. 4, 5 and B have become suitable electrical source such as a conventional no heated to electron-emltting temperatures. current will flow in the reactance coils I3 and I4, producing a counter-voltage in the auxiliary windings II and I9. and I2 and I8 respectively, thereon. The circuit of my invention has been designed so that the voltage induced in the several auxiliary windings II, I9, I2 and I8 counteracts to a large extent the voltage in the electrode heatin windings 9, I and I6, thus insuring a relatlvely low current through the electrodes. 3, 4,16 and 5 during lamp operation. This may be accomplished by connecting the auxiliary windings II, i9, I2 and I8 with their polarities such that the voltages of the reactance coils pass in a direction opposite to that of the transformer voltage,

Another advantage of the circuit of my invention over many of the conventional fluorescent lamp circuits is the manner in which the condenser 2! is connected in the circuit. In many of the conventional circuits the condenser is usually connected in series in the electrode pie-heating circuit. In the circuit of my invention the condenser is not connected in the electrode pro-heating circuit. The condenser 2| is connected in series with the reactance coil 13 while the electrode pro-heating circuit is a separate one through the windings 9. Ill and I6. This feature is a very important one from a practical point of view.

When a capacitive lamp or a capacitive lamp starter in a conventional fluorescent lamp circuit becomes defective and fails to operate normally, a voltage considerably higher than normal operating voltages will be across the condenser. Since the condensers normally employed are usually rated at about 330 volts, the higher voltages of the order of about 580 volts Whichwould be across the condenser when one of the conditions mentioned above existed would cause the condenser to break down. This result is not normally obved however at this time. Usually the fixture serviced by replacing the lamp or the starter the case may be. However, when this is done, both lamps will operate inductively and-cause excessively high currents in the transformer. By the time one notices that the transformer is "burning up, considerable damage has been done,

This condition. which is not at all uncommon, obviated in the circuit of my invention because, due to the arrangement of separate electrode preheating windings, the pre-heating current doesn't flow in the condenser and therefore when this type of situation arises the condenser will not be affected.

I have found that the circuit of my invention gives very satisfactory performance when the several elements thereof are characterized by values substantially of the following order:

Electrode preheating windings 9, ill and IB about 18 volts.

Auxiliary windings I2 and I8about volts.

Lil

It is to be understood however that, of course, these values necessarily will not be the same when the CilCUll of my invention is employed with fluorescent lamps or other electric gaseous discharge devices other than the conventional 40 watt fluorescent lamps with which my circuit has been illustrated and described.

Not only does the circuit of my invention permit the elimination of a starter and provide fast starting of the lamps but it also permits the lamps to be dimmed if desired. This is particu lorly advantageous in certain installations such as theatres for example where it is desired to turn the lamps out by gradually cutting down the amount of light emitted rather than out the light olf instai'itnneously. This is made possible by reason of the fact that there is always some current in the lamp electrodes and therefore the line voltage can be cut down gradually from -120 volts to about 60 or 65 volts, in the case of 40 watt lamps. before the discharge across the lamps ceases.

What I claim is:

1. A circuit for two electric gaseous discharge devices, each having a filamentary electrode disposed at each end thereof, said circuit comprising a transformer having a primary winding, a pair of windings separate from the primary winding. and a winding defined by a tapped portion of the primary Winding; two reactance coils, each having two auxiliary windings thereon, each coil being connected to the primary of said transformer and in series with one end of an electrode in each of said devices; one end of each of said pair of windings separate from the primary winding being connected through one of the auxiliary windings on each of the reactance coils to the same end of the electrodes to which the reactance coils are connected, and the other end of these windings being connected directly to the other end of these electrodes; the winding defined by the tapped portion of the primary windlng being connected in parallel to the other electrodes in said devices, one end of said winding being connected directly to one end of each of said electrodes, and the other end of said winding being connected to the other end of said electrodes through the other auxiliary Winding on each of said reactance coils.

2. The combination of claim 1, in which one of said reactance coils is connected to the primary of said transformer through a capacitive reactance in series.

CARL M. LARIME.

REFERENCES CITED The following referen't'ss are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,406,328 Atherton s Feb. 14, 1922 l,980,534 Kirsten Nov. 13, 1934 2298.589 Reitherman et al. Oct. 13, 1942 2332.455 Maurer Oct. 19, 1943 2,340,348 Sleplan s-.. Feb. 1, 1944