CA1234863A - Power distribution system - Google Patents

Abstract

Abstract of the Disclosure A limited power, gaseous discharge lighting system particularly suitable for use with suspended ceilings and for safe installation without shock or fire hazard and for rearrangement by non-electricians without special tools or experience. The system uses flexible cables to supply individual relocatable gaseous discharge lighting fixtures, and the flexible cables are individually plugged into receptacles which furnish power strictly limited to permit the safe use of the flexible cables, plugs and receptacles. High frequency operation permits two lamp operation with rated light output despite the power limitation which permits less power than normally is available to such fixtures.

Description

3~363 POWER DISTRIBUTION SYSTEM

Summary of the Invention This invention deals generally with systems for electric lamp and discharge devices and more specifically with a power distribution system for gaseous discharge lamps which operate at low voltage and with limited power.
One need only walk into a typical large office building to appreciate the great amount of power consumed by lighting.
In most buildings virtually the entire ceiling of each floor is covered by row upon row of fluorescent light fixtures.
Unlike residential lighting where specific work areas are lit by individual, moveable, lamps, most usable commercial space is usually lit to full work level light intensity required by the most demanding task.
This is necessary because when the building is first con-structed the lighting designer cannot anticipate the exact loca-tions where light is needed, and yet in commercial and in~ustrial areas only trained electricians are permitted to install standard ceiling lighting fixtures operating at rated electrical power.
The designer, therefore, fully lights the entire area r rather than force the later occupant to become involved with formal restructuring of the lighting systems. Such procedures lead to energy wasted by using excess lighting.
One approach to saving more of this energy has been to circulate the heat generated by the lighting system to use it for building heat, but such solutions gain nothing in those localities and seasons when cooling rather than heating is required.
The present invention approaches the problem from a different aspect, that of using a distribution system which can easily and safely be rearranged by non-electricians. Such a system brings to lighting systems what has existed in wall structures for many years. Most large office complexes use moveable room dividers to permit flexibility of office arrangements.
However, prior to the present invention, no rearrange-ment of lighting was possible without using the services of a trained electrician for revising the lighting--the equivalent of moving permanently fixed walls.
The present invention is a unigue distribution system which permits changes of lighting arrangements in a much more casual manner, and is particularly advantageous for use with suspended ceilings. In such installations, the lighting fixtures themselves are typically supported by the ceiling grid and can be removed and relocated easily. In the prior art, however, the fixtures are wired with permanently attached armored cables connecting the fixtures to electrical power, so that the simple mechanical installation is completely negated by the semirigid electrical hook-up.
The present invention uses flexible cable and plug-in electrical connections, but does so in a safe manner, which protects against fire and shock hazards.
This new system of power distribution is such that it would prevent shock and fire hazards even in the familiar :

g ~3~ 3 ~ 3 --context of a typical residence. For instance, one embodiment is designed so that even if a child were to insert a metal object into the power receptacle and touch it, no harm would likely result.
Moreover, all embodiments of the present invention furnish fire protection from a short circuit.
Again, in the context of a typical residence, if the flexible cable of the present invention were used as an extension cord, but, contrary to all safety considerations, placed under a high traffic area of carpet where damage to the cable insulation was likely to occur, nevertheless, there would be little risk of fire even if a short circuit did occur.
These results are supported by information from the National Electrical Code which permits the use of certain limited voltage and limited power systems which are considered to be free of shock ha~ard and free of fire hazard according to Articles 725 and other of the National Electrical Code published by National Fire Protection Association, Quincy, Massachusetts~ Typical familiar applications which fall into this category are door bell circuits, ringing circuits in telephone systems, and fire alarm systems.
The present invention therefore furnishes a safe, versatile lighting system for use in commercial and industrial locations. This is accomplished by limiting the lighting system power to specific predetermined values which have been generally accepted for other low power circuits by the National Electrical Code, and thereby enabling the use of a flexible cable in systems which are fire and/or shock hazard free. A plug-in connecting system is also used for the cabIes.
In the National Electrical Code, Class 2 power limited circuits, which are considered shock and fire hazard free, include circuits in which the open circuit voltage does not exceed 30 volts and having load currents inherently limited to 8.0 amperes, or, if not inherently limited to that ~23~63 value but including overcurrent protection, such protection must interrupt the curxent at 100 divided by the maximum voltage.
Such Class 2 circuits are premitted by the Code -to 5 use flexible cable wiring on the load side o the circuit.
The flexible cable assembly used in the present invention meets the National Electrical Code standards, and is generally conventional plastic covered multi-conductor cable. Class 2 circuits require only that the conductors and 10 insulation be "suitable for thé particular application," while r Class 3 specifies certain material (copper) and insulation sizes, which are not very stringent by industry standards.
Class 3 circuits, which are considered only fire hazard free, also permit flexible cables, and are defined to 15 include voltages up to 150 volts, providing the overcurrent protection interrupts the circuit current at one ampere.
Below 100 volts, Class 3 circuits which are inherently current limited to 1000 divided by the maximum voltage must also have overcurrent protection set at 1/10 this value. Class 3 20 circuits with inherent current limitation of 150 divided by the maximum voltage need no overcurrent protection.
Both classes limit the volt-amperes (VA) of the load to 100.
The present invention, although not specifically 25 covered by the Code, operates within the limits set by Class 2 and Class 3 operation to yield a system which permits relocation of suspended ceiling light fixtures safely without special tools or experience and with little danger of shock or fire.
As will be apparent from the following and detailed description-s, the specific limits for voltage and current parameters can be adjusted by the seLection of specific component values. Thus, reduced fire hazard can be accomp-lished by the use of components which limit the voltage and power to certain values, and reduced fire and reduced shock hazard can be accomplished by selecting components to further .q c - 5 - ~Z34~63 :
-~ limit the voltage and power.
In both situations, the basis of the presen-t invention remains the same, to limit the voltage and -the power to levels which will prevent fire and shock hazard while still assuring sufficient voltage and powar to opera-te the light fixtures.
The invention uses a power limited source -to operate gaseous discharge lamps with sufficient light output for commercial and industrial installations. One of the means of accomplishing this is raising the frequency above power line frequencies.
In the invention herein, "power limiting means"
defines an element or elements which will limit power to no more than a predetermined output, herein 100VA. A fuse is not a power limiting means because it will deliver in excess of its rating for a finite period before it interrupts.
Such above definition is in conformity with the National Electric Code.
All embodiments of the invention use power 10 from rated voltage electrical lines, 120 volts, 240 volts, 277 volts, etc. In one embodiment, these sources are connected to a number of rated voltage operated inverter power supplies, each such power supply providing for a plurality of outputs, with each such output being of limited power and of relatively high frequency. This goal is aided by a sub-stantial inductive internal impedance, which is operative to limit the output current from each individual output to a maximum not exceeding a predetermined valueO The invention will limit power output regardless of the electrical power source capacity. The invention will limit output power to not exceed a predetermined value regardless of the load conditions including short circuit.
The outputs of the inverter power supply, supplying high frequency~ but voltage and current limited power, are connected ~o a plurality of paris of ~23~

- flexible conductor wires which are pr~vided With easy plug-in connection at each of the several outputs of the individual inverter power supplies.
The flexible conductor wires connect to and feed the high frequency, limited voltage and current power to a plurality of fluorescent lighting units, each such unit comprising one or more fluorescent lamps and a matching network operative to derive the requisite lamp operating voltages and currents from one of the inductively current limited, high frequency, limited voltage outputs of one of the inverter power supplies.
The power provided to each lighting unit is provided at a high power factor, thereby permitting a power level of nearly 100 Watts to be provided to each lighting unit, which, with the indicated high frequency operation and with presently available high-effici~llcy fluorescent lamps, can provide nominal light O~ltpUt.
The invention therefore furnishes a versatile lighting system in which several permanently wired and located inverter power supplies can supply power to a multitude of relocatable fluorescent light fixtures, each connected to an inverter by flexible cable and plug-receptacle combinations, but safely detachable and relocatable without experienced electricians.
The present invention, then, in one aspect, resides in a lighting system adapted to be powered from an ordinary electric utility power line and comprising:
a central power conditioner adapted to ~onnect with said power line and comprising a plurality of se~arate output means, each such output means having current limiting means and being operative to provid~ an e~sctrical output that is individually and manifestly limited in terms of continuously available electric power to a leveI that is substantially lower than the electric power available directly from said power line~ said level being low enough to be considered to be reasonably safe from a fire initiati~n viewFoint;~

123~63 -6a-a plurality of lighting units, each lighting unit comprising an electric lamp and having electric input means operable to receive the electrical output from one of said output means; and a flexible cord and connect means for each lighting unit, said cord and connect means being operative to provide aisconnectable connection between one of said output means and the input means of one of said lightiny units whereby each individual lighting unit is connectable directly with the central power conditioner;
thereby permitting a lighting unit to be moved and re-located relative to, as well as to be removed and/or disconnected from, said power conditioner.
In another aspect, the present invention resides in a lighting system adapted to be powered from an ordinary electric utility power line and comprising:
a number of power conditioners connected with said power line at different spaced-apart points therealong, each of said power conditioners having a

2~ plurality of separate power-limited outputs, each such output being limited in terms of maximum power extractable therefrom on a continuous basis to about 100 Watt or less;
a set of lighting fixtures for each power conditioner, each lighting fixture having: (i) an electric lamp, ii) matching means operative to match the input characteristics of said lamp to the output characteristics of one of said outpu~s, and iii) terminal means connected with said matching means and operative to receive the output from one of said outputs; and connect cords operative to provide connection between said lighting fixtures and said power-limited outputs, with each one of these connect cords being used ! for connecting between one of said outputs and said terminal means of one of said lighting fixtures wher by each said individual lighting fixture is connected directly with one of the central.power conditioners.

~3~ 3 -6b-The present invention urther provides a lighting system for a suspended ceiling, said suspended ceiling having a grid structure and being suspended below a permanent ceiling, said system comprising:
a numher of central power conditioners mounted some distance apart on said permanent ceiling, each of these power conditioners being connected with an ordinary electric utility power line and having a plurality of separate Volt-Amp-limited power outputs, with each such power output current limiting means and being operative to supply an AC
output current that is manifestly limited in magnitude to a degree such that the maximum energy flow extractable from each such power output stays below a level that is considered hazardous from a fire initiation viewpoint;
a set of lighting fi~tures for each central power conditioner, each of said lighting fixtures being mounted in said grid structure and having: i) an electric lamp, ii) matching means operative to match the electrical input characteristics of said lamp with the electrical output characteristics of said power outputs, and iii) electrical terminal means connected in circuit with said matching means and operable to receive power from one of said power outputs; and for each lighting fixture, a connect cord by which to connect that lighting fixture to one of said Volt-Amp-limited power outputs whereby each said individual lighting fixture is connected directly with one of the central power conditioners.
Bri~f Description of the Draw~ngs FIG. 1 schematically illustrates, from an overall systems viewpoint, the preferred embodiment of the invention; and shows a plurality of rated voltage operated inverter power supplies, each providing powerline isolated, current limited, high frequency AC
voltage for operation of a number of individual gaseous -discharge lighting units.

~23~863 -6c-FIG. 2 schematically illustrates the first embodiment of one of said plurality of rated voltage operated power supplies and its multiple current limited outputs and corresponding individual connections with a number of gaseous discharge lighting units.
FIG, 3 schematically illustrates electrical - 7 ~ ~234~63 circuit details of a first embodiment of a fluorescent lighting unit usable within the system shown in PIGS. 1 and 2.
FIG. 4 is a simplified schematic diagram of an alternate embodiment of a resonant circuit system for use in the described system.
FIG. 5 is a simplified schematic diagram of a third alternate embodiment of a resonant circuit system for use in the described system.
FIG. 6 is a simplified schematic diagram of a system of power limitation operable directly at rated power line frequencies.
Detailed Description of the Invention The preferred embodiment for the invention is shown in simplified block diagram form in FIG. 1.
In FIG. 1, a source 12 of rated voltage is applied to a pair of power line conductors 14 and 16.
Connected at various points along this pair of power line conductors are a number of power line operated inverter power supplies 18, 20 and 22.
To each such rated voltage operated power supply are connected a number of gaseous discharge lighting units 24, 26 and 28. The number may be different for different power supplies at different system arran~ements.
FIG. 2 illustrates in further detail one of the typical power supplies of FIG~ 1 and its associated li~hting units.
This typical power supply 18 is powered from power line conductors 14 and 16.
Inside 18, power line conductors 14 and 16 are directly connected with a rectifier-filter combination 30, the substantially constant DC output voltage of which is applied to an inverter 32.
The output from inverter 32 is a 30 kHz AC
voltage, which AC voltage is applied to the primary winding 38 of an isolation transformer 34.

12~ 3 The output o transformer 34 is provided from its secondary winding 36 and is a 30 kHz AC voltage of approximately 30 Volt RMS magnitude. Secondary winding 36 is electrically isolated from primary winding 38.
By way of a number of inductor means 40, 42 and 44, this transformer output voltage is supplied to a number of power output receptacles 46, 48 and 50, respectively.
By way of male plugs 52, 54 and 56 conduction wire-pairs 58, 60 and 62 and female plugs 64, 66 and 68, the output receptacles 46, 48 and 50 are connected with input receptacles 70, 72 and 74 on lighting units 76, 78 and 80, all respectively.
The assembly consisting of rectifier and filter means 30, inverter 32, transformer 34 and the output receptacles 46, 48 and 50 is referred to as power supply 18.
FIG. 3 illustrates one of the typical lighting units referred to in FIG. 2 as 76, 78 and 80. This 20 typical lighting unit is referred to as 76 and has a power input receptacle 70.
Inside lighting unit 76 is a voltage step-up auto-transformer 82, the input side of which is directly connected with input receptacle 70 and the output side . 25 of which is directly connected across a series combination of two f~uorescent lamps 84 and 86.
Fluorescent lamp 84 has two cathodes 88 and 90;
and fluorescent lamp 86 has two cathodes 92 and 94.
Auto-transformer 82 has three secondary windings 30 96, 98 and lOO, all of which are electrically isolated r from one another as well as from the input side of auto-transformer 82.
Secondary winding 96 is directly connected with cathode 88; secondary winding 98 is directly connected 35 with a parallel-connection of cathodes 90 and 92, and secondary winding 100 is directly connected with cathode 94.
, .

- 9 - ~3L23~363 Capacitor 102 is connected directly across the output side of auto-transformer 82.
Operation of the First Embodiment The operation of the system and circuits illustrated in FIGS. 1 to 3 may be explained as ollows:
In FIG. 1, the pair of powerline conductors 1 and 16 provides rated voltage power to each and every inverter power supply: 18, 20 and 22.
Each inverter power supply converts its raked input voltage to a plurality of powerline isolated power limited, high frequency, limited magnitude AC voltage outputs. Each such AC voltage output is directly connected with a lighting unit, powering this lighting unit by way of said power limited, high frequency, limited magnitude AC voltage.
FIG. 2 shows how said powerline isolated, power limited, high frequency, limited magnitude AC voltage outputs are obtained.
The powerline voltage is applied to a rectifier-filter combination of a conventional construction; and theoutput from this rectifier-filter combination is a sub-stantially constant DC voltage. This DC voltage is inverted by conventional inverter 32, as described in U. S. Patent No. ~,184,128, to a 30 kHz AC voltage of essentially squarewave shape.
This 30 kHz squarewave inverter output voltage is applied to the primary winding of voltage step-down, high frequency transformer 34; which transformer is of conventional construction.
This transformer also pxovides for electrical isolation between its primary and secondary windings, thereby providing for the extra safety of powerline isolation of the AC voltage outputs from power supply 18.
The output of the secondary winding 36 of transformer 34 is a 30 kHz unlimited power, essentially squarewave shaped AC voltage with a substant~ially constant ~23~3 RMS magnitude of about 30 Volts; which AC voltage is provided to the power output receptacles 46, 48 and 50 of power supply 18 by way of inductors 40, 42 and 44.
Thus, the magnitude of the current avallable at any one of these power output receptacles is limited by the reactance of the inductor connected in series circuit with that receptacle. .The magnitude of the reactance of this inductor is chosen such that the current resultiny when a given output receptacle is short circuited is no higher than 8 Amp RMS.
. The high frequency AC voltage output from each of the power output receptacles is applied to a fluorescent lighting unit by way of a conduction wire pair and its associated male plug and female receptacle.
FIG. 3 shows how the individual lighting units work and more particularly, how the ballasting of the fluorescent lamps is accomplished in conjunction with series inductances 40, 42 and 44.
The output from one of the output receptacles of power supply 18 is applied by way of a conduction wire pair to p3~er input receptacle 70 of lighting unit 76, from where it is applied directly to a voltage step-up transformer 82, the output of which is applied directly across two series connected fluorescent lamps 84 and 86.
The actual ballasting of the two fluorescent lamps is accomplished by way of resonant interaction between capacitor 102 which is connected in parallel across the two series connected fluorescent lamps 84 and 86 and the particular inductor 40 located in the power supply 18 feeding power to the lighting unit 76.
In other words, part of the ballasting function for the two fluorescent lamps 84 and 86 of lighting unit 76 is accomplshed by way of inductor 40 within the power supply 18.
The rest of the circuit functions within lighting unit 76, such as the provision of cathode heating .... .

. ~L23~363 by way of the three secondary windings on transformer 82, is accomplished in manners well understood by those skilled in the art.
It should be noted that any one of the lighting units, such as lighting unit 76, may consist of any number or types of lamps; and that these lamps might.even be mounted in different locations or located in diferent lighting structures or fixtures. However, within the context of the present invention, it is important that all the lamps powered from a single output from any of the inverter power supplies, be ballasted as a single entity and that the aggregate Volt-Ampere product drawn from this output not exceed 100 VA.
It should also be noted that, due to the resonant matching of the fluorescent lamp loads to the source of high frequency power, the current drawn from the inverter power supplies by the different lighting units will be nearly sinusoidal in waveshape; and it will be substantially in phase with the fundamental component of the .squarewave AC voltage outputs provided by these power supplies. As a result, the power drawn by the lighting units is drawn with a high power factor, which implies a maximization of the power available within a set limit of Volt-Amperes. Moreover, resulting electro-magnetic interference by radiation from lamps andconductor wires is minimized.
Yet another thing that should be noted is the fac~ that capacitor 102, which is shown in FIG. 3 as being connected across the primary side of transformer 82, may just as well be connected across the secondary side of transormer 82. In fact, to provide for the desired power factor correction, capacitor 102 may even be connected in series with the output or input side of transformer 82.
FIG. 4 depicts an alternate embodiment of a resonant circuit ballast in simplified schematic form.
This ballast circuit, like that shown in FIG. 3, is used - 12 _ 1234~3 with inverter 3~, series inductor 40, output receptacle 46, male plug 52, wire-pair 58, female plug 64 and input receptacle 70, in a system as previously described in regard to FIGS. 1 and 2.
Fixture 104 of FIG. 4 however diff~rs from fixture 76 depicted in FIG. 3 in that, in addition to the direct wire connection between the primary windiny of transformer 82 and secondary winding 96, the direct wire connection is supplemented by capacitor 106 connected between thP primary winding and secondary winding 100.
; The circuits of ~IG. 3 and FIG. ~ both operate in the following manner. Before lamps 84 and 86 ignite the voltage supplied by inverter 32 across input receptacle 70 is near-resonant because of the combination of inductor 40 and capaci or 102. As a result, because of Q-multiplica~
tion, the voltage developed across capacitor 102, and therefore across lamps 84 and 86 as well, is ver~ high causing ignition of the discharge in lamps 84 and 86.
Upon ignition, the resonant circuit of inductor 40 and capacitor 102 will become loaded which reduces the Q-multiplication, which causes the voltage across receptacle 70 to be reduced.
It should be n~ted that the safety goals of the circuits are met in all conditions since detaching any of the plug-receptacle combinations, or even breaking the flexible cable, terminates the resonant condition and leaves the open circuit condition as one with low voltage and power limitation through inductor 40.
The difference in operation of the circuit of FIG. 4 caused by the addition of capacitor 106 is that capacitor 106 adds phase correction and power factor improvement. Without capacitor 106, if the unloaded inductor 40 and capacitor 102 combination is substantiaIly resonant, then the loaded combination, with the load in parallel with capacitor 102 is necessarily inductive rather than resonant. The addition of capacitor 106 - 13 ~3~3 neutralizes this inductive factor and greatly improves the power factor. Moreover, it should be noted that capacitor 106 is only effective when the lamps are operative and therefore does not affect the resonant starting.
In both FIG. 3 and FIG. 4, however, the cathode heating circuits have a decided ef~ect in the starting operation. Initially, before cathodes 88, 90, 92 and 94 have reached their normal operatlng temperature, and are therefore relatively low in resistance, they create a heavier current load on the circuit. Through transformer 82 they therefore load the resonant circuit of inductor 40 and capacitor 102, similar to the action described above during lamp operation; and the voltage a~ross the lamp is momentarily limited on start-up untll the cathodes have reached operating temperature. As the cathode temperatures increase, their resistances increase, the currents decrease, and the loading action on transformer 82 diminishes, thereby permitting the Q-multiplication to increase. The voltage across capacitor 102 therefore does not instantaneously jump on start-up and, more importantly, it does not subject the lamps to a higher voltage until the cathodes are properly heated. This action, which may be called "soft"
starting, increases the life and reliability of lamps 84 and 86.
FIG. 5 depicts another embodiment which is a highly simplified version of the present invention. This embodiment, which can also be used in the system shown in FIGS. 1 and 2, includes ballast circuit 108 as shown in U. S. Patent 3,710,177 which, operating in conjunction with source limiting inductor 40 of the present lnvention, operates single lamp 110, but as described previously assures that voltage and power levels are always within the limits for shock and fire safety. In FIG. 5, when voltage is applied to lamp 110 by inverter 32 through limiting inductor 40, capacitor 112, in series combination with limiting inductor 40, causes the circuit to resonate ~" . ~

- 14 - ~ ~3~3 and a high voltage is impressed across lamp 110. Also, the high resonant current passes through cathodes 11~ and 116 to overheat them and encourage fast starting~ When the discharge is establishe~ withln lamp 110, the discharge current acts as a shunt resistance across capacitor 112 shifting the operation point somewhat and reducing both the voltage across the lamp and the current through cathodes 114 and 116. Capacitor 118 is an optional addition to the patented circuit to better adjust it ~or optimum operation.
When the current operates at or near resonance, power factor is optimized, and, because of the sinusoidal current, radio frequency interference is also reduced. An additional advantage of the configuration of FIG. 5 is the self compensation of cathode heating current with lamp output, providing for decreased cathode current when cathode heating is provided by the discharge current. Lamp voltage is characteristically inversely proportional to discharge current. As such, increasing discharge current is accompanied by decreasing lamp and capacitor ~oltage, which results in diminished cathode current and increased lamp efficacy. Conversely, as lamp output and the discharge current decrease, cathode filament heating current will increase, and provide additional cathode heating to compensate for the reduction in heating resulting from the diminished discharge current.
FIG. 6 is a further embodiment of the present invention and is perhaps the simplest of all. Most important, it uses conventional power source 120 operating at rated power line frequency and voltage and also uses conventional fluorescent lamp fixture 126. It differs ~rom conventional plug-in fluorescent lamp circuits, however, in that, because of proper choice of value for inductors 122 and 123,-located within power supply 121, all circuit elements on the load side of inductors 122 and 123 are protected from shock hazard and ~ire hazard.

- 15 _ ~234~3 Capacitor 124 is located in series with limiting inductor 122 and selected so that, considering inductive components in standard lamp fixture 126, it will cause the entire circuit to resonate at the frequency of power supply 120. Thus the series circuit of limiting inductor 122, capacitor 124 and lamp fixture 126, includiny reactances within the fixture and from the system wiring, are designed to be resonant at the power supply frequency, even though that frequency is as low as 60Hz. Inductor 122 is also selected with the criteria that its reactance must be such that, if a short circuit occurs on its load side, the ampere output will be limited to a safe valve. It should be noted that part of the inductance of the resonant circuit can be located other than within power supply 121.
In specific terms, that means that for the fire safety case, the reactive impedance of induc~or 120 must be at least 120 ohms for a 120 volt rated power source, and at 60Hz that requires an inductance of approximately 0.32 Henries. Capacitor 124, to resonate the circuit, assuming no additional inductance in lamp fixture 126, must have a value of approximately 22 microfarads.
The shock safety case requires a lower voltage of 30 volts maximum and therefore requires only a 0.9 ohm inductive reactance. At 60Hz this is available from an approximately .0024 Henries inductance which would require an approximately 2900 microfarad capacitance for resonance.
Such values could therefore ~urnish a safe, versatile lighting system which can be rearranged by virtually anyone.
It is to be understood that the form of this ; invention as shown is merely a preferred embodiment.
Various changes may be made in the function and arrange-ment of parts; equivalent means may be substituted for those illustrated and described; and certain features may be used independently from others without departing from - 16 _ ~23~3 the spirit and scope of the invention as defined in the following claims.
For example, sodium vapor lamps may be used in plaee of conventional fluorescent lamps, and multiple lamps may be located in a single ixture with eaeh lamp separately powered by a circuit sueh as that shown in FIG. 5. Conversely, multiple lamps in a eireuit sueh as that shown in FIG. 3 could each be plaeed in different localities but be interconnected. Moreover, in many of the embodiments, the locations of inductive and capacitive reactances could be interchanged and resonanee and power limitation could be maintained. This is particularly so for the circuit of FIG. 6.

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A lighting system adapted to be powered from an ordinary electric utility power line and comprising:
a central power conditioner adapted to connect with said power line and comprising a plurality of separate output means, each such output means having current limiting means and being operative to provide an electrical output that is individually and manifestly limited in terms of continuously available electric power to a level that is substantially lower than the electric power available directly from said power line, said level being low enough to be considered to be reasonably safe from a fire initiation viewpoint;
a plurality of lighting units, each lighting unit comprising an electric lamp and having electric input means operable to receive the electrical output from one of said output means; and a flexible cord and connect means for each lighting unit, said cord and connect means being operative to provide disconnectable connection between one of said output means and the input means of one of said lighting units whereby each individual lighting unit is connectable directly with the central power conditioner;
thereby permitting a lighting unit to be moved and re-located relative to, as well as to be removed and/or disconnected from, said power conditioner.

2. The lighting system of Claim 1 wherein each of said electrical output means is manifestly limited to provide a maximum continuous power output on the order of 100 Watt or less.

3. The lighting system of Claim 1 wherein one of said lighting units comprises a fluorescent lamp and ballasting means therefor.

4. The lighting system of Claim 1 wherein the magnitude of the voltage of said electrical output is substantially constant for as long as the current being drawn therefrom is not so high as to cause the resulting output power to exceed said level.

5. The lighting system of Claim 1 wherein said power conditioner means comprises frequency conversion means, whereby the frequency of the voltages provided at said output means is different from that of the voltage provided by said power line.

6. A lighting system for a suspended ceiling, said suspended ceiling having a grid structure and being suspended below a permanent ceiling, said system comprising:
a number of central power conditioners mounted some distance apart on said permanent ceiling, each of these power conditioners being connected with an ordinary electric utility power line and having a plurality of separate Volt-Amp-limited power outputs, with each such power output having current limiting means and being operative to supply an AC output current that is manifestly limited in magnitude to a degree such that the maximum energy flow extractable from each such power output stays below a level that is considered hazardous from a fire initiation viewpoint;
a set of lighting fixtures for each central power conditioner, each of said lighting fixtures being mounted in said grid structure and having: i) an electric lamp, ii) matching means operative to match the electrical input characteristics of said lamp with the electrical output characteristics of said power outputs, and iii) electrical terminal means connected in circuit with said matching means and operable to receive power from one of said power outputs; and for each lighting fixture, a connect cord by which to connect that lighting fixture to one of said Volt-Amp-limited power outputs whereby each said individual lighting fixture is connected directly with one of the central power conditioners.

7. A lighting system adapted to be powered from an ordinary electric utility power line and comprising:
a number of power conditioners connected with said power line at different spaced-apart points therealong, each of said power conditioners having a plurality of separate power-limited outputs, each such output being limited in terms of maximum power extractable therefrom on a continuous basis to about 100 Watt or less;

a set of lighting fixtures for each power conditioner, each lighting fixture having: i) an electric lamp, ii) matching means operative to match the input characteristics of said lamp to the output characteristics of one of said outputs, and iii) terminal means connected with said matching means and operative to receive the output from one of said outputs; and connect cords operative to provide connection between said lighting fixtures and said power-limited outputs, with each one of these connect cords being used for connecting between one of said outputs and said terminal means of one of said lighting fixtures whereby each said individual lighting fixture is connected directly with one of the central power conditioners.