US2482894A - Operating system for vapor arc lamps - Google Patents

Description

Sept. 27, 1949. L. F. BIRD OPERATING SYSTEM FOR VAPOR ARC LAMPS 4 Shee'tS-Sheei 1 Filed Oct. 7, 1947 LAMP UQRENT 5 mKNOL L/NE VOLTAGE I INVENTOR. LESTER F. 5/20 BY M A 7' TORNEY Sept. 27, 1949. F. BIRD 2,482,894

OPERATING SYSTEM FOR VAPOR ARC LAMPS Filed Oct. 7, 1947 4 Sheets-Sheet 2' 2 l/NE lNPUT q CURRENT Q =1 MP VOLTA E LAMP CURRENT L w VOL TA 65' INVENTDR. [5750 F- aver) A TTORNEY Sept. 27, 1949.

Filed 00%.. 7,;1947

FEAST/V5 OHMS 1.. F. BIRD 2,482,894

OPERATING SYSTEM FOR VAPOR ARC LAMPS 4 Sheets-Sheet 5 THEORET/CAL REACTANCE REQU/QED AC ANCE MASUE D [AGTANCE )QfQU/RED IN SEE/ES W/TH LAMP 7'0 PRODUCE CONST WATTAGE IN LAMP.

LINE VOLTAGE INVENTOR. A 5 TEE F. 5/20 Sept. 27, 1949. F. BIRD 2,432,894

OPERATING SYSTEM FOR VAPOR ARC LAMPS Filed Oct. '7, 1947 4 Sheets$heet '4 v LAMP CURRENT IRCU/T PERFORMANCE THOUT 04 'WITH AND WITHOUT CAPACI T012 MP WATT/46E LAMP CURRENT WITH CA PA c/rcm 4501a WA TTA 65 WITH CA PA C/TOR VOLTS AND AMPERES MP VOLT/4 WITH CAPA C/TOR WI TH DU 7' L/NE VOLTAGE v INVENTOR. 1 ES TEE F. BIRD flaw A TTORNEY Patented Sept. 27, 1949 Lester F. Bird, Newark, N. J assignor to Hanovia Chemical'& Manufacturing Company, Newark, N. J., a corporation of New Jersey AppIication October 7, 1947, Serial No. 778,503 2 Claims. (01. 31s 235) This invention deals with an operating system for vapor arc lampsand more particularly 1200p erating circuits for metal vapor arc lamps and discharge tubes.

Metal vapor arc lamps and discharge usuall operated from high reactance transformers whereby the' secondary reactance limits the current that will flow from the transformer secondary to any resistance load between a short circuit condition and the maximum input o f'the arc lamp. In the high pressure low voltage are lamp the voltage drop across the lamp is always low at the time of starting, for instance as low as about 5%12% of the final operating value, and the effect on the transformer is almost equivalent to a short circuit. It is common practice to design the transformerso that the starting currents are about 1.45 times the usual operating currents and so that during operation the voltage drop across the transformer secondary is the voltage drop across thelamp itself. The reactance of the transformer secondary serves to stabilize the arc lamp and keep it lighted. Such reactance is inductive in character and the current in the lamp circuitlags behind the induced secondary voltage causing a lagging power factor for the supply, currents. With such a transformer, the wattage consumed by the lamp varies approximately as the square of the percentage change of line voltage supply, Le. a 10% change in line voltage results in a 21% change in lamp wattage. Fluctuations in line supply voltages therefore result in wide variations in the light output of the lamp and continuous readjustment of the input connections is required on the transformer if the lamp wattage is to be maintained at or near a constant value. 'Such variations in light and the consequent adjustments necessary to compensate for these variations are very cumbersome in the.

operation of such devices.

It is one object of this invention to provide an operating system for vapor arc lamps and discharge tubes, "being supplied from alternating current sources, whereby the input to said lamps and discharge tubes, and also the light generated thereby, are rendered less affected by the voltage of the operating supply circuits and are substantially freed from variations resulting from fluctuations in the supply voltage; It is another object of this invention to provide an operating circuit for metal vapor arc lamps and discharge tubes capable of automatically eliminating Wide variations in the light .output charge tubes.

Further objects and advantages .of this inventubes are of said lamps and dis-' tion will become apparent from the following description and claimsin connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic representation of an operating circuit for metal'vapor arc lamps and discharge tubes according to the invention, and I Figures 2, 3, 4 and 5 are graphic representatisns supplementing the descriptive portion of this invention as indicated therein.

Referring to Figure 1, I and 2 are supply lines of variable alternating current voltage from which an enclosed vapor arc lamp is tobe operated. A high reactance transformer 3 having a primary 4, a secondary 5 and a leakage reactance 6, such that the secondary short circuit current lies betweenll and 1.7 times the normal lamp operating current, a is diagrammatically illustrated. The series capacitor"! has between 1 and a 6 times the kva. rating of the arc lamp 8. Since conditions of operation and during all parts of the current cycle have anadequate reactance in series with it to maintain stability. It is inherently impossible to operate with only a series capacitor for the stabilizing means in the circuit of my invention because of an oscillating condition which follows the use of only series capacitative reactance for the stabilization of the arc lamp. I actually utilize a resultant capacitative reactance for stabilization because the capacitor employed is in an effective series connection with an inductive reactance, leaving the sum total, for both, capacitive. The reactance of the series capacitor 1 is chosen to be approximately twice the value of theinductive reactance '6, leaving a resultant capacitative reactance in the circuit essentially equal in value to 6 since in this combination the inductive reactance and the capacitative reactance substract from each other. Since the resultant reactance is the one which provides stabilization for the'lamp, and in this case is capacitative; the lamp'is actually operating from a capacitative reactance andso the currents flowing in the secondary or lamp circuit are l of leading power factor. g V

The characteristics of this circuit are radically and essentially different in this combination than,

would be expected'from a simple study of the electrical componentsand it has been found that there is not a condition of resonance existing in the secondary circuit since the lamp will not operate if the inductive reactance of 6 and the capacitative reactance of 1 are adjusted to be nearly equal. Such a neutralization results in too low a series stabilizing reactance to permit operation of the arc lamp, as previously stated, and there must always be adequate residual reactance in the circuit. This requirement eliminates any condition of resonance which could exist. However, it has been found that with .this circuit, the fluctuations in power consumption of the lamp which occur where the capacitor is omitted, are greatly reduced when the series capacitor of the proper size is added. The value of this capacitor has been found to be about 1 /2 to 6 times the kva. rating of the lamp. For example, if the wattage of the lamp is 500 watts, the va. of the capacitor is about 1500 or 3 times that of the lamp. Since the same current flows through the capacitor that flows through the lamp, the voltage drop across the capacitor becomes about 3 to 5 times the voltage existing across the lamp.

Since the inductive reactance 6 is most commonly built into the structure of the transformer, and is an electrical rather than a physical entity, it is not possible to show by actual voltage measurements the voltage existing across reactance 6. However, the voltage coming out of the secondary of the reactive transformer, which is a measure of the voltage existing across the series system composed of the capacitance and the lamp, can be measured and is usually found to be approximately equal to the voltage across the capacitor. It has been found that by properly proportioning the coils of the transformer 4 and the ratio of the windings 3 tothe winding 5, the secondary circuit is reflected through the transformer to the primary circuit, in such a manner, that the energy in the secondary circuit assumes a condition of high stability, similar to a condition of resonance, and is merely excited by the primary input. The variations in the primary input voltage then no longer appear in equal or greater value in the secondary circuit. Actually, it has been found possible to reduce the fluctuations in the secondary circuit so that they are less than 5% of those in the primary circuit. Moreover, it has been found that the transformer can be so proportioned that the overall reactance existing between the secondary circuit and the primary can be greatly reduced or neutralized by the condensive reactance reflected back through the transformer from the secondary circuit. This substantial neutralization of reactance causes the power factor of the primary current to approach unity although it is always on the leading side.

Therefore, referring to Figure 2, it is found that as the primary voltage is varied from a relatively low value, Say 15% of normal, through normal, to possibly 125% of normal, that the input currents to the operating lamp circuit can be made to fall with rising voltage, go through a minimum and again rise. Under other conditions, referringto Figure 3, there is a fall from the start at the 75% of normal value, continuously, up to 125% of normal. Under proper conditions, the input power factor throughout this range can remain substantially constant and relatively high, approximately 80 to 90%. Thus the condition exists where the primary voltage and primary current can be changing rapidly and radically while the secondary currents are remaining substantially constant and unaffected.

. open circuit secondary volts and adapted to run a 3100 ohm discharge tube at about 110-120 milliamps, I add a capacitor in series with the lamps having a reactance of about 5280 ohms at the input frequency and having a voltage drop at about 600 volts, to give a va. rating of about 66 voltamperes with a lamp rating of about 36. I have found that with this combination of circuit elements, the wattage in the discharge tube varied less than plusor minus 5% while the line voltages varied between about of normal and about of normal. The normal variations in wattage were reduced by the application of my invention to about 8% of those normally to be expected with the usual operating transformers.

The exact electrical interpretation of these results has not been worked out and at the present time is not clearly understood. However, this in no wise reduces the usefulness or practicability of the electrical system. It has been determined, however, that the flux density of the magnetic circuit in the transformer mustbe at or near the saturation of the iron. If the flux density in the transformer core is not near the knee of the saturation curve, reactions will exist causing variations in current to occur in thesecondary circuit, with changes in primary input voltage, that will be much greater than is the case when the flux density is, near the saturation point. I, therefore, employ a transformer of such a design that with normal input voltage on the primary, the iron is operating at or near the knee of the saturation curve for the core material. The magnetizing currents flowing in the primary winding vary considerably with changes in the input voltage as does the inductance of the primary as shown in Figure 2. r

In Figure 4 is shown a curve illustrating the variations in reactance which are required in series with the arc lamp to accomplish a condition of constantcurrent during variations of the primary voltage, and-it will be observed from this curve that on the particular transformer and are lamp circuit on which this curve was taken that the reactance in series with the arc lamp varied from a value of about 50 ohms with an input voltage of up to 110 ohms at an input voltage of 200 volts and up to 147 ohms at 225 volts and upto ohms at 250 volts. The second of the curves illustrates the actual measurements taken on a transformer to illustrate how closely the actual electrical circuit corresponds with the theoretical reactance required for such a stabilized system; It can be readily seen, therefore, that the stabilization which results from the application of my invention is excellent, and that the advantages of the use of such a system are satisfactory in practical application.

Therefore, my invention accomplishes desirable results in an entirely automatic manner such that variations in the line supply voltage of 10% will not cause a 21% change in the wattage consumption of the lamp, but less than a 5% change in wattage. In most cases, it is possible to have even less than this change, thereby reducing the fluctuations which normally would exist by more than 75%. Referring to Figure 5, I accomplish this desirable result without requiring any manual adjustment, and the results are secured automatically. Moreover, in addition to limiting the variations of power consumption in the arc lamp, I also have altered the power requirements from the supply lines so that a leading power factor is achieved. Such a result is very desirable because of the fact that most electrical equipment involving transformers draws lagging currents from the lines and, therefore, equipment which draws a leading current is generally helpful in stabilizing such voltage fluctuations as are commonly found. All of these desirable results are achieved by the addition of components in accordance with my invention to the usual electrical circuits normally employed with this type of arc lamp.

Moreover, my invention also limits the starting currents flowing to the arc lamp such that a greatly reduced load can be placed on the electrodes of the lamp during the warm up period and so increases the life expectancy and the service secured from the lamp.

What I claim is:

1. A discharge device operating system for maintaining a substantially constant wattage, comprising in combination a transformer having a magnetic core structure and mounted thereon a primary input coil and a secondary inductive coil in spaced relation to each other with a high reluctance magnetic shunt between said coils, a stabilizing wattage circuit comprising a capacitor connected between one of the terminals of said secondary coil and said discharge device, said stabilizing wattage circuit being operative under 7 Number a series stabilizing reactance provided by-the reactance of a secondary coil wound about a core material operating at the knee of the saturation curve for the core material in combination with the reactance provided by a capacitor having a kva. rating of about 1 to 6 times the kva. rating of said discharge device.

2. An arc lamp operating system for maintaining a substantially constant Wattage, comprising in combination a transformer having a magnetic core structure and mounted thereon a primary input coil and a secondary inductive coil in spaced relation to each other with a high reluctance magnetic shunt between said coils, a stabilizing wattage circuit comprising a capacitor connected between one of the terminals of said secondary coil and said discharge device, said stabilizing wattage circuit being operative under a series stabilizing reactance provided by the reactance of a secondary coil wound about a core material operating at the knee of the saturation curve for the core material, so that the secondary current is limited by leakage reactance under short circuit conditions to a valve between 1.7 and 1.1 times the normal operating current of the lamp, in combination with the reactance provided by a capacitor having a kva. rating of about 1% to 6 times the kva. rating of said lamp.

LESTER F. BIRD.

REFERENCES CITED The following references are of record. in the file of this patent:

UNITED STATES PATENTS Name Date 2,334,567 Lord Nov. 16, 1943 2,346,621 Sola Apr. 11, 1944 2,423,031 Kurtz June 24, 1947

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