US3519881A

US3519881A - Starting and operating circuit for any of a plurality of different discharge lamps

Info

Publication number: US3519881A
Application number: US807710A
Authority: US
Inventors: Joseph C Engel; Robert T Elms; George A Kappenhagen
Original assignee: Westinghouse Electric Corp
Current assignee: Cooper Industries LLC
Priority date: 1969-03-17
Filing date: 1969-03-17
Publication date: 1970-07-07
Anticipated expiration: 1987-07-07
Also published as: DE2011663A1; ES377416A1

Description

y 7, 7 J. c. ENGEL EIAL 3,519,881

STARTING AND OPERATING CIRCUIT FOR ANY OF T A PLURALITY OF DIFFERENT DISCHARGE LAMPS Filed March 17, 1969 FEEDBACK CONTROL I FIG. I.

FEEDBACK CONTROL FIG. 2.

' HIGH VOLTAGE LOW ENERGY PULSE :2 X LINE VOLTAGE HIGH ENERGY PULSE NORMAL LAMP OPERATING VOLTAGE FIG. 3.

United States Patent US. Cl. 315-236 Claims ABSTRACT OF THE DISCLOSURE Apparatus for starting and operating any of a plurality of gaseous discharge lamps which have starting requirements varying from a high voltage pulse to an intermediate voltage, high energy pulse. The apparatus utilizes an AC switching means and ballasting inductor which are in series with the lamp to be operated. A control means is responsive to a lamp operating condition in order to actuate the AC switching means to limit the period of time during half cycles of AC energizing potential that the lamp is operatively connected to the energizing source. In the operation of the apparatus, when the energizing potential is initially applied to the apparatus, a transformer generates a high voltage pulse to initiate operation of those lamps which require such a starting pulse. A saturable electrical magnetic element, which forms a part of the apparatus, becomes saturated in a time period of from about 2 microseconds to about 100 microseconds after the energizing potential is initially applied to the apparatus. After the saturable electrical magnetic element becomes saturated, the lamp ballasting inductor and a capacitor form a series resonant circuit in order to apply across the lamp an intermediate voltage, high energy pulse, to initiate operation of those lamps which require such intermediate voltages for starting.

CROSS REFERENCE TOO RELATED APPLICATIONS In copending application Ser. No. 807,659, filed concurrently herewith by Joseph C. Engel and Robert T. Elms, and owned by the present assignee, is disclosed a ballasting apparatus which will operate any of a plurality of discharge devices having varying voltage and current operating characteristics in order to operate a discharge device at about a predetermined wattage rating. The apparatus disclosed in the present application is particularly useful in conjunction with a ballasting apparatus as disclosed in this copending application.

BACKGROUND OF THE INVENTION The usual discharge device operates with a negative voltampere characteristic and some form of current limiting ballasting is required to prevent a runaway discharge. In recent years there have been developed several new types of discharge devices which have achieved some limited commercial success for applications such as outdoor flood lighting and similar uses, and these discharge devices have promise for use in interior lighting. Such devices are commercially marketed under various trade designations and broadly can be categorized as mercury-metal halide, highpressure, discharge devices and sodium or sodium-mercury discharge devices which utilize a light-transmitting refractory envelope formed of polycrystalline alumina or similar material. Various combinations of such devices are also known. These recently developed devices, together with the well-known high-pressure mercury-vapor discharge devices, are used for high-bay factory lighting, highway and floodlighting, and stadium lighting to name a few of the applications.

One of the problems with the use of such discharge devices is that each type has different voltage and current operating characteristics, even though the wattage ratings might be the same. The effect of this is that each lamp type requires a different ballast which is specially tailored to start and operate the lamp. The problem is further complicated by the fact that in the field of mercury-metal halide lamps, a myriad of different metal halide additives can be used to achieve different illumination effects and each different combination of metal halide additives often changes the lamp starting and operating characteristics sufficiently to require a different lamp starting and operating ballast. Since the ballast represents a substantial portion of cost of the fixture, once the user is committed to one specific type of lamp, he normally cannot readily change lamp types without incurring substantial expense in changing the lamp starting and operating ballast.

It is known in the art to ballast discharge devices by actuating a bilateral switch to vary the input to the lamp so that the average energy input is maintained at about a predetermined value. Such an apparatus is disclosed in US. Pat. No. 3,222,572, dated Dec. 7, 1965. A circuit which functions in a generally similar fashion is also disclosed in US. Pat. No. 3,265,930, dated Aug. 9, 1966.

SUMMARY OF THE INVENTION It is the general object of the present invention to pro Vide an improved apparatus for starting and operating any of a plurality of gaseous discharge devices having starting requirements which vary from a high voltage pulse to an intermediate voltage, high energy pulse.

The foregoing object of the invention, and other objects which will become apparent as the description proceeds, are achieved by providing an apparatus which comprises input terminals adapted to be connected across a source of AC potential of predetermined value. An AC switching means and a ballasting inductor means and the lamp to be operated are connected in series across the input terminals. A control means which is responsive to a lamp operating condition actuates the AC Switching means in order to limit the period of time during half cycles of AC energizing potential that the lamp is operatively connected by the AC switching means to the source of AC energizing potential. A transformer has a primary winding connected in series with a first capacitor, and this primary winding and first capacitor are connected in parallel with the series-connected ballasting inductor and the lamp to be operated. A second capacitor and seriesconnected saturable electrical magnetic element, which can comprise a transformer secondary or an inductor, are connected in parallel with the lamp to be operated. The saturable electrical magnetic means is adapted to saturate in a time period of from about 2 microseconds to about microseconds after the AC switch is closed. Immediately upon closing of the AC switch, the transformer generates the very high voltage pulse across the lamp to be operated. Thereafter the saturable electrical magnetic means becomes electrically saturated and this causes the transformer effectively to be removed from the circuit and the ballasting inductor and the second capacitor form a series resonant circuit to develop an intermediate voltage across the second capacitor, which voltage in turn is applied across the lamp to be operated. If the lamp operation has not already been initiated by the high voltage pulse previously delivered by the transformer, the lamp operation is initiated by the intermediate voltage, high energy pulse which is thereafter developed.

3 BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, reference should be had to the accompanying drawings, wherein:

FIG. 1 is a circuit diagram of the preferred embodiment of the present apparatus;

FIG. 2 is a circuit diagram of an alternative embodiment of an apparatus constructed in accordance with the present invention;

FIG. 3 is a graph of voltage vs. time generally illustrating the starting and operating voltages which are developed by the present apparatus in each half cycle of energizing potential; and

FIG. 4 illustrates one embodiment of a network which can be used to parallel the AC switch in order to prevent excess voltage transients from being developed thereacross.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The standard mercury lamp which is designed to operate with the power input of about 400 watts operates with a voltage of from about 130 to 140 volts and an operating current of from 3.1 to 2.9 amperes. Such a lamp is relatively easy to start and a pulse of about 250 volts will normally start such a lamp. The mercury-metal halide lamps which are designed to operate with the power input of about 400 watts will normally have an operating voltage varying from 125 to 145 volts and an operating current of from about 3.1 to 2.8 amperes. Such lamps are somewhat more difiicult to start and normally require a high energy pulse of about 450 volts. This will vary somewhat depending upon the type of metal halide which is utilized. Lamps using a polycrystalline alumina envelope and a mercury-sodium fill, when operated with the power input of about 400 watts, have an operating voltage which can vary from 70 to 160 volts and an operating current which can vary from 5.6 to 2.5 amperes. Such lamps for starting require a voltage pulse of low energy of at least 2000 volts, and preferably about 4000 volts. Summarizing the starting characteristics for the three basic lamp types enumerated above, the mercury-sodium lamps require an extremely high voltage pulse in order to initiate operation. The mercurymetal halide lamps, in contrast, require an intermediate voltage, high energy pulse to initiate their operation. With respect to the straight mercury lamps, any starting voltage which Will initiate the operation of the mercury-metal halide lamps will also start the straight mercury lamps.

The foregoing specific starting and operating characteristics have been considered for lamps which have a rating of 400 watts. Lamps which have higher or lower wattage ratings will normally have slightly modified starting characteristics, although a starting circuit which will provide the aforementioned high voltage pulse, followed by the intermediate voltage, high energy pulse, will normally start any of these lamps.

The lamp operating apparatus as disclosed in the aforementioned copending application Ser. No. 807,659, filed concurrently herewith, essentially comprises apparatus which is responsive to a lamp operating condition to actuate the AC switching means in order to limit the period of time during half cycles of AC energizing potential that the lamp is operatively connected by the AC switch to the source of AC energizing potential. In this aforementioned copending application, the control means actually measures the voltage drop across the lamp and the current therethrough, in order to develop a control signal which is proportional to the wattage consumed by the lamp. Such a wattage indicative control signal is required to operate any of a plurality of different lamps where the voltage and current operating characteristics can vary over such a wide range. It should be understood, however, that the present apparatus can operate with a control means which is responsive to any type of lamp operating condition, examples being the current through the lamp or the measured brightness of the lamp, and such current or brightness responsive control means are generally known.

Referring to the drawings, the preferred apparatus of the present invention is shown in FIG. 1 and generally comprises input terminals 10 which are adapted to be connected to a source 12 of AC potential of a predetermined magnitude. Usually, the apparatus will be adapted to be connected across a 210-270 volt line or a 242-312 volt line. An AC solid-state switching means 14', ballasting inductor 16 and the lamp 18 to be operated are connected in series across the input terminals 10. A capacitor 19 connects across the input terminals 10 to correct the power factor, as is conventional. As an example, for a 2l0-270 volt line, the rating of capacitor 19 is 2933 ,uf. A control means 20 which is responsive to a lamp operating condition actuates the AC solid-state. switching means 14 to limit the period of time during half cycles of AC energizing potential that the lamp is operatively connected to the source 12 of AC energizing potential. The control means 20 preferably is responsive to lamp wattage and this circuit is described in complete detail in the aforementioned copending application Ser. No. 807,659, filed concurrently herewith. The control means 20 is connected to the lamp input leads by means of a current transformer 22 to develop a signal which is indicative of lamp current, and the control means is also connected by leads 24 across the lamp 18 to develop a signal which is indicative of lamp voltage.

In the preferred form of the invention, the ballast 16 comprises a part of an autotransformer 26. The transformer 26 has a primary winding 28 connected in series with a first capacitor means 30, with the primary winding 28 and capacitor 30 connected in parallel with the ballasting inductor 16 (the secondary winding in this embodiment) and the lamp 18 to be operated. A saturable inductor 32 and a second capacitor means 34 are connected in series across the lamp 18 to be operated. The saturable inductor 32 is adapted to saturate in a time period of from about 2 microseconds to about microseconds after the AC switch 14 is closed. In this embodiment, prior to saturation of the inductor 32, the voltage applied across the lamp is that which is developed by the autotransformer 26, which as an example is 4000 volts. This voltage is applied directly across the lamp 18 since the saturable inductor 32 substantially blocks any current flow through this electrical path. As an example, the first capacitor 30 has a capacitance of about 0.05 ,uf. and the capacitor 34 has a capacitance of about one microfarad. If the lamp to be started is a mercury-sodium lamp which uses a polycrystalline alumina envelope, this initial high voltage pulse of about 4000 volts will break down the discharge path between the lamp electrodes and initiate lamp operation. If the lamp is of the mercury-metal halide type, however, the initial pulse will not have sufiicient energy to initiate operation of the lamp. A shunt resistor 31 having a value of 30 k9, for example, may be connected across the lamp 18 if the lamp socket does not have a sufiiciently high voltage rating.

In the preferred form of the invention, the inductor 32 saturates in about twenty microseconds although the period required for saturation can vary from about 2 microseconds to about 100 microseconds. Once the inductor 32 is saturated, the ballasting inductor 16 and second capacitor 34 will form a relatively low impedance, series resonant circuit and the potential developed across the capacitor 34 in this condition of series resonance is approximately 450 volts. This is sufficient to initiate the discharge through the mercury-metal halide lamp and once operation is initiated, the energy stored in the one microfarad capacitor 34 will be discharged through the lamp, in order to form the high-energy pulse necessary to initiate operation of such a lamp 18. The ordinary mercury lamp will be initiated by either the high voltage pulse delivered by the transformer or the intermediate voltage, high energy pulse delivered by the series resonant LC circuit. In this starting apparatus, the pulse and line voltages are additive.

An alternative embodiment of the present apparatus is shown in FIG. 2 wherein the autotransformer 26 is replaced by a ballasting inductor 36. Across the line is connected a saturable transformer 38, the primary 40 of which is connected in series with the first capacitor 30, and the series-connected primary 40 and capacitor 30 are connected in parallel with the inductor ballast 36 and the lamp 18 to be operated. When AC switch 14 is initially closed, the transformer 38 generates the high voltage pulse across the lamp 18 and after the transformer 38 is saturated, in a time period of from about 2 microseconds to about 100 microseconds, it is essentially removed from the circuit and the inductor 36 and capacitor 34 form a series resonant LC circuit, with the current flow through the secondary winding 42 of the nowsaturated transformer 38, which thus comprises a saturable electrical magnetic element. Under these conditions of saturation, the intermediate voltage developed across the capacitor 34 is sufficient to start the lamp 18, similar to the embodiment as shown in FIG. 1.

The general operating characteristics for either of the embodiments shown herein'before are set forth in the graph illustrated in FIG. 3. On each succeeding half cycle of AC energizing potential, after the switch 14 is turned on, there is initially developed, in about two microseconds, a high voltage, low energy pulse, followed by an intermediate voltage, high energy pulse which approximates twice the line voltage. This in turn is followed by the application of the normal lamp operating voltage, once the second capacitor has discharged.

This present apparatus also prevents what is known in the art as lamp dropout. This can occur at low line voltages or even at high line voltages when sodiummercury lamps are only energized during a relatively small proportion of a half cycle of energizing potential. Also, during warm-up of some mercury-metal halide lamps, the difierent rates at which the discharge-sustaining materials vaporize can cause such drop out, that is, a cessation of operation. In accordance with the present invention, a high voltage pulse or an intermediate voltage, high energy pulse is applied across the lamp at the start of each half cycle, thereby insuring the continued operation of the lamp.

With the starting arrangement of the present invention, there may be a tendency to develop excessive voltage transients across the AC switch 14, particularly when high line voltage conditions are encountered. In FIG. 4 is shown a paralleling network 44 which is designed to display a low impedance upon application thereacross of a voltage which exceeds the voltage rating of the AC solid-state switch 14. In this embodiment, three Zener diodes 46 each having a rating of 160 volts are connected in series with three similar, oppositely connected Zener diodes 48, along with a 330 ohm resistor 50. For use with a 600 volt AC switch, the total Zener voltages desirably are from 450 to 520 volts. This network could be readily replaced by other networks which will achieve the same function, such as opposed avalanche-type diodes which will serve to protect the AC switch 14 from excessive voltage transients.

It will 'be recognized that the objects of this invention have been achieved by providing apparatus for starting and operating any of a plurality of gaseous discharge devices having starting characteristic requirements which vary from a high voltage pulse to an intermediate voltage, high energy pulse.

While preferred embodiments of the invention have illustrated and described in detail, it is tobe particularly understood that the invention is not limited thereto or thereby.

What is claimed is:

1. Apparatus for starting and operating any of a plurality of gaseous discharge devices having starting characteristic requirements which vary from a high voltage pulse to an intermediate voltage high energy pulse, said apparatus comprising:

(a) input terminals adapted to be connected to a source of AC potential of predetermined value;

(b) AC switching means and ballasting inductor means and said lamp to be operated connected in series across said input terminals, and control means responsive to a lamp operating condition to actuate said AC switching means to limit the period of time during half cycles of AC energizing potential that said lamp is operatively connected by said AC switching means to said source of AC energizing potential;

(c) transformer means having a primary winding con nected in series with a first capacitor means, and said primary winding and said first capacitor means con nected in parallel with said series-connected ballasting inductor means and said lamp to be operated; and

(d) series-connected saturablemagnetic electrical means and second capacitor means connected in parallel with said lamp to be operated, said saturable electrical means adapted to saturate in a time period of from about 2 microseconds to about microseconds after said AC switch is closed, and prior to saturation of said saturable electrical magnetic means, said transformer means generating across said lamp to be operated said high voltage pulse, and after said saturable electrical magnetic means is saturated, said second capacitor means and said ballasting inductor means forming a relatively low impedance series resonant circuit to develop across said second capacitor means and thus apply across said lamp tobe operated said intermediate voltage.

2. The apparatus as specified in claim 1, wherein the secondary Winding of said transformer means comprises said saturable electrical magnetic means.

3. The apparatus as specified in claim 1, wherein additional capacitor means is directly connected across said input terminals.

4. The apparatus as specified in claim 3, wherein said AC switching means is protected from excess voltage transients by a paralleling network which displays a low impedance upon application thereacross of a voltage which exceeds the voltage rating of said AC switching means.

5. Apparatus for starting and operating any of a plurality of gaseous discharge devices having starting characteristic requirements which vary from a high voltage pulse to an intermediate voltage high energy pulse, said apparatus comprising:

(0) transformer means having a. primary winding connected in series with a first capacitor means, and said primary winding and said first capacitor means connected in parallel with said series-connected ballasting inductor means and said lamp to be operated; and

(d) seriesconnected saturable inductor means and second capacitor means connected in parallel with said lamp to be operated, said saturable inductor means adapted to saturate in a time period of from about 2 microseconds to about 100 microseconds after said AC switch is closed, said saturable inductor means prior to saturation substantially blocking current flow through said second capacitor means during which time said transformer means generates across said lamp to be operated said high voltage pulse, and after said saturable inductor means is saturated, said second capacitor means and said ballasting inductor means forming a relatively low impedance series resonant circuit to develop across said second capacitor means and thus apply across said lamp to be operated by said intermediate voltage.

6. The apparatus as specified in claim 5, wherein additional capacitor means is connected directly across said input terminals.

7. The apparatus as specified in claim 6, wherein said transformer means constitutes an autotransformer, and the secondary winding of said autotransformer constitutes said ballasting inductor means after said lamp is operating.

8. The apparatus as specified in claim 7, wherein said AC switching means is protected from excess voltage transients by a paralleling network which displays a low impedance upon application thereacross of a voltage References Cited UNITED STATES PATENTS 2,924,749 2/ 1960 Filberich 315146 3,170,085 2/ 1965 Genuit 315227 3,394,689 7/1968 Bell 123148 3,405,316 10/1968 Osial et a1. 315 243 JAMES D. KALLAM, Primary Examiner R. F. POLISSACK, Assistant Examiner U.S. Cl. X.R.