Patent Application
20080258629
This invention relates in general to fluorescent lamps, and more particularly, to an apparatus, lamp assembly and method for facilitating power extraction from a fluorescent lamp, independent of or in combination with controlling and modulating the temperature of a portion of the fluorescent lamp to maintain efficiency thereof.
Fluorescent lamps are sensitive to ambient temperature. Depending on lamp type, the optimal ambient temperature at which light output of different lamp types is maximized varies. For example, T8 fluorescent lamps are optimized at a temperature of 25° C., while T5 fluorescent lamps have an optimal ambient temperature of 35° C. If the ambient temperature is higher or lower than these optimal temperatures, the light output and efficacy of the lamps are significantly reduced.
Thus, to maintain optimal light output and efficacy of a fluorescent lamp, it is advantageous to maintain ambient temperature at its optimum. However, it is difficult to maintain the ambient temperature surrounding a fluorescent lamp at a given temperature since such ambient temperature controls usually require more electric energy than needed to power the lamp itself.
A fluorescent lamp contains a larger quantity of liquid mercury than will become vaporized during operation. This excess liquid mercury condenses at the coldest point, or so-called “cold spot” of the lamp. This condensation of liquid mercury is the primary cause of light output efficacy degradation under colder than optimal operating conditions. However, by directly controlling the lamp's cold spot temperature, it is possible to control the quantity of vaporized mercury, thereby controlling the light output and lamp efficacy. While the cold spot temperature is optimum, the light output is maintained at its peak, regardless of ambient temperature. Location of the cold spot varies with lamp type. For example, the cold spot of a T8 fluorescent lamp is located near the center of the lamp bulb, while the cold spot of a T2 or T5 fluorescent lamp is located at the end cap of the lamp bulb.
Although numerous attempts have been made in the art to control the cold spot temperature of a fluorescent lamp, and thereby enhance efficiency of the fluorescent lamp, existing control mechanisms typically require redesign of the fluorescent lamp itself, or may only be applied to fluorescent lamp facilities wherein the ambient temperature is within a relatively narrow range. Therefore, alternative solutions are still needed to maintain a lamp's optimal cold spot temperature, particularly for certain facilities such as outdoor facilities, refrigerated and/or unconditioned warehouses. Additionally, a more efficient mechanism for powering a temperature regulation device is deemed advantageous, particularly when retrofitting a temperature control mechanism into an installed fluorescent lamp assembly.
The shortcomings of the prior art are overcome and additional advantages are provided through the provision, in one embodiment, of an apparatus which includes a magnetic structure comprising a magnetic core and a power extraction winding disposed at least partially around the magnetic core. The magnetic core is sized and configured to surround at least a portion of a fluorescent lamp having plasma current passing therethrough when the fluorescent lamp is powered ON. When the fluorescent lamp is powered ON, with the magnetic core surrounding at least the portion of the fluorescent lamp, plasma current of the fluorescent lamp forms a primary winding of a transformer defined by the magnetic structure and plasma current of the fluorescent lamp passing therethrough, and power is magnetically coupled from the plasma current of the fluorescent lamp to the power extraction winding of the magnetic structure, e.g., for use in powering a device to be coupled thereto.
In another aspect, a lamp assembly is provided which includes a fluorescent lamp and a magnetic structure. The magnetic structure surrounds a portion of the fluorescent lamp, and includes a magnetic core and a power extraction winding disposed at least partially around the magnetic core. The magnetic core surrounds at least a portion of the fluorescent lamp having plasma current passing therethrough when the fluorescent lamp is powered ON. When the fluorescent lamp is powered ON, plasma current of the fluorescent lamp forms a primary winding of a transformer defined by the magnetic structure and plasma current of the fluorescent lamp passing therethrough, and power is magnetically coupled from the plasma current of the fluorescent lamp to the power extraction winding of the magnetic structure for use in powering a device when coupled thereto.
In a further aspect, a method is provided which includes: providing a magnetic structure including a magnetic core and a power extraction winding disposed at least partially around the magnetic core, the magnetic core being sized and configured to surround at least a portion of a fluorescent lamp having plasma current passing therethrough when the fluorescent lamp is powered ON; disposing the magnetic core at least around the portion of the fluorescent lamp; and wherein when the fluorescent lamp is powered ON, plasma current of the fluorescent lamp forms a primary winding of a transformer defined by the magnetic structure and plasma current of the fluorescent lamp passing therethrough, and power is magnetically coupled from the plasma current of the fluorescent lamp to the power extraction winding of the magnetic structure for use in powering a device when coupled thereto.
Further, additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Generally stated, provided herein are an apparatus and method for extracting power from a fluorescent lamp, for example, for controlling temperature of a portion of the fluorescent lamp to maintain efficiency thereof. The apparatus includes a magnetic structure having a magnetic core and a power extraction winding disposed at least partially around the magnetic core. The magnetic core is sized and configured to surround at least a portion of the fluorescent lamp having plasma current passing therethrough (i.e., when the fluorescent lamp is powered ON). When the fluorescent lamp is powered ON, with the magnetic core surrounding at least the portion thereof, plasma current of the fluorescent lamp forms a primary winding of a transformer defined by the magnetic structure and plasma current of the fluorescent lamp passing therethrough, and power is magnetically coupled from the plasma current to the power extraction winding of the magnetic structure for powering a device electrically coupled thereto. In one embodiment, the device is a temperature modulation component which varies temperature of at least a portion of the fluorescent lamp, for example, to facilitate maintaining a cold spot temperature of the fluorescent lamp within a desired range of an optimum temperature.
In certain embodiments, the magnetic core is a ferromagnetic material with a composition chosen to have a Curie point which functions as a switch mechanism for discontinuing power extraction from the plasma current of the fluorescent lamp when the magnetic core surrounding the portion of the fluorescent lamp reaches its Curie point. In this embodiment, the temperature modulation component includes a resistive heating element which is disposed adjacent to the cold spot of the fluorescent lamp, for example, on an inner surface of the magnetic core, with the magnetic core at least partially encircling the cold spot of the fluorescent lamp. Although various aspects of the present invention are described herein below with reference to a T5 fluorescent lamp, the concepts presented are applicable to other sizes and types of fluorescent lamps. Advantageously, it is easier to control the cold spot temperature of certain fluorescent lamps, such as a T5 fluorescent lamp, due to the accessibility of the cold spot location (i.e., near one end thereof). Further, T5 fluorescent lamps are generally more sensitive to colder ambient temperatures since they are optimized at a higher temperature than other typical fluorescent lamps, and therefore experience a greater degradation of light output at colder temperatures.
Field demonstrations have indicated that the use of T5 fluorescent lamp technology in high ceiling applications can reduce energy use by 30% to 50% over a typical metal-halide lighting system. Fluorescent lamps have also been shown to be effective in outdoor applications, saving 30% over high-pressure sodium lamps in a streetlight application, due to their ability to provide lighting spectrally tuned to the human nighttime visual system. However, end users have been apprehensive about using T5 lamps in spaces such as unconditioned or refrigerated warehouses, colder areas of grocery stores or other buildings, or in outdoor applications because of the lamp's sensitivity to temperature. Thus, presented herein is a simple, inexpensive apparatus that can be easily installed on a fluorescent lamp (such as a T5 fluorescent lamp) to maintain its cold spot temperature, light output, and efficacy, making these lamps appropriate for use in a much wider range of applications than currently available, thus increasing their market penetration, and reducing lighting energy use dramatically.
The solution presented herein is a magnetic apparatus that couples to the plasma current of the fluorescent lamp, and employs a magnetic structure, which together with the plasma current, defines a transformer to extract power from this lamp current. As used herein, “plasma current” refers to the current passing through the plasma within an active fluorescent lamp, and “fluorescent lamp” refers to any fluorescent light, including fluorescent tubes such as T2, T5 and T8 fluorescent lamps.
The mercury 220, which exists at a stable vapor pressure equilibrium point of about 1 part per 1,000 inside of the fluorescent tube, is likewise ionized, causing it to emit light in the ultraviolet (UV) region of the spectrum predominantly at wavelengths of 253.7 nm and 185 nm. The efficiency of fluorescent lighting owes much to the fact that low pressure mercury discharges emit about 65% of their total light at the 254 nm line (and about 10%-20% of the light emitted in UV is at the 185 nm line). The UV light is absorbed by the bulb's fluorescent coating, which re-radiates the energy wavelengths: two intense lines of 440 nm and 546 nm wavelength appear on commercial fluorescent tubes to emit visible light. The blend of phosphors controls the color of the light, and along with bulb's glass, prevents the harmful UV light from escaping.
As is well known, a fluorescent lamp typically employs a ballast 210 which is powered by an alternating voltage 212. Ballast 210 regulates current flow through the fluorescent lamp, and depending on the lamp implementation, could be a resistive ballast, magnetic ballast or electronic ballast.
On a T5 fluorescent lamp, the cold spot (where the mercury 220 accumulates), is located at one end of the lamp, for example, at the metallic end cap about 2 mm from the glass envelope on the surface where the lamp label is printed. The cold spot temperature is usually optimally approximately 10° C. degrees higher than the optimal ambient temperature under a normal operation condition. To maintain optimal output of a T5 fluorescent lamp, therefore, it is advantageous to maintain the cold spot temperature at, for example, approximately 45° C., which is 10° C. higher than its optimal ambient temperature of 35° C.
As briefly noted above, presented herein is a relatively simple, inexpensive apparatus which can be employed to extract power from a fluorescent lamp, and modulate temperature of the fluorescent lamp, for example, to increase temperature at a cold spot of the fluorescent lamp.
In
In operation, magnetic structure L1240 of the power extraction apparatus magnetically couples to the fluorescent lamp's plasma current to extract power from the plasma current. In one embodiment, the magnetic core of the transformer is one of a ring-shaped structure or a cylindrical-shaped structure sized and configured to slip over and encircle a portion of the fluorescent lamp. When so positioned, the lamp's plasma current forms a one-turn primary winding for the transformer, and the power extraction winding encircling a portion of the magnetic core is a secondary winding of the transformer. Power extracted to the power extraction winding is used to drive, for example, a heating circuit such as switch mechanism SW1250 and resistive heating element R1230. In one embodiment, switch mechanism SW1250 comprises a temperature sensor which closes to heat the cold spot of the fluorescent lamp when needed, and opens once the cold spot reaches or exceeds a preset temperature to remove power from the resistive heating element.
Those skilled in the art should note that the power extraction apparatus presented herein (e.g., comprising magnetic structure L1240) could be employed to power a non-temperature-related device(s) as well (e.g., any low power electronic device). For example, the magnetic structure could be used to signal failure of the fluorescent lamp or fluorescent lamp luminaire, for example, through a failure to generate a signal indicative of the proper operation of the fluorescent lamp. These signals could be accumulated at a central location of a facility, and allow a failure message to be generated upon detection of the absence of a signal.
Advantageously, opening 420 of magnetic core 400 is sized and shaped for positioning of the apparatus of
Operationally, plasma current established within the fluorescent lamp between electrodes 202, 203 (
The device's switching mechanism opens when the cold spot, or more particularly in this embodiment, the magnetic core, has reached the predefined shut-off temperature (i.e., the selected Curie point). It is desirable not to continue heating the lamp after it has reached the desired cold spot operating temperature because excessive heating wastes power. The temperature-based switching mechanism stops the heating effect once the desired temperature is reached. In the embodiment of
Low Curie temperature ferromagnetic, and more particularly, ferrite materials, are known in the art. For example, reference an IEEE article entitled “The Characteristics of Ferrite Cores with Low Curie Temperature in their Application”, IEEE Transactions on Magnetics (June 1965), the entirety of which is hereby incorporated herein by reference. As is well known, the Curie point or temperature is a temperature above which a ferromagnetic substance looses its ferromagnetism and becomes paramagnetic. In typical transformer applications, the Curie point is as high as possible, to ensure continued operation of the transformer. However, in the
An apparatus such as described above can be installed on or integrated with a fluorescent lamp in a number of ways. For example, as a ring-shaped structure or cylindrical-shaped structure, the apparatus could be separately fabricated from the fluorescent lamp, and retrofitted thereon by easily slipping around the lamp bulb in an existing lighting installation by a lamp installer, such as an end user or maintenance person. Advantageously, no wiring is required in the installation. Alternatively, the apparatus could be integrated as part of the luminaire structure, for example, as part of a lamp socket structure in a luminaire. The apparatus could be a ring or cylinder structure attached to a socket that the lamp tube is inserted through to reach the socket contacts. Luminaire manufacturers could apply such an apparatus to their luminaire products. Still further, the apparatus could be attached as a structure surrounding the metal sleeve (e.g., ferrule) at the end of a fluorescent lamp tube. Fluorescent lamp manufacturers could implement such a device on their lamp products. Still further, the apparatus could be integrated with the lamp (e.g., lamp bulb) itself. This would allow lamp manufacturers to develop fluorescent lamps appropriate for lower temperatures.
The
The implementation depicted in
To summarize, provided herein is an apparatus which includes a magnetic structure comprising a magnetic core and a power extraction winding disposed at least partially around the magnetic core. The magnetic core is sized and configured to surround at least a portion of the fluorescent lamp, for example, having plasma current passing therethrough when the fluorescent lamp is powered ON. When the fluorescent lamp is powered ON, with the magnetic core surrounding at least the portion of the fluorescent lamp, plasma current of the fluorescent lamp forms a primary winding of a transformer defined by the magnetic structure and plasma current of the fluorescent lamp passing therethrough. Power is magnetically coupled from the plasma current of the fluorescent lamp to the power extraction winding of the magnetic structure, for example, for use in powering a device to be coupled thereto.
In one implementation, the device is a temperature modulation component, such as a resistive heating element. Power magnetically coupled into the power extraction winding powers the temperature modulation component to vary temperature of at least a portion of the fluorescent lamp. A temperature dependent switch mechanism may also be provided for controlling powering of the temperature modulation component. In one implementation, the magnetic core includes a ferromagnetic material with a composition chosen to have a Curie point which functions as the temperature dependent switch mechanism for discontinuing temperature modulation of at least a portion of the fluorescent lamp by discontinuing power extraction from the plasma current of the fluorescent lamp when the magnetic core surrounding the portion of the fluorescent lamp reaches its Curie point.
In further aspects, the temperature modulation component is a resistive heating element configured for disposition adjacent to a cold spot of the fluorescent lamp when the apparatus is in use with the fluorescent lamp powered ON. The magnetic structure may include an inner surface defining an opening sized and configured to receive a portion of the fluorescent lamp therein. In this implementation, the resistive heating element may be disposed at least partially along the inner surface of the magnetic core, and when in use, the magnetic core surrounds at least a portion of the cold spot of the fluorescent lamp. In one implementation, the magnetic core is a ring-shaped structure or a cylindrical-shaped structure sized to encircle the fluorescent lamp. Although applicable to any fluorescent lamp, the concepts presented are particularly advantageous for one of a T5, T4, T3, T2 or T1 fluorescent lamp, with the cold spot disposed at one end of the fluorescent lamp.
The apparatus can be separately fabricated from the fluorescent lamp, or integrated with the fluorescent lamp or a fluorescent lamp luminaire, such as a socket thereof.
In another aspect, a method is provided which includes: providing a magnetic structure including a magnetic core and a power extraction winding disposed at least partially around the magnetic core, the magnetic core being sized and configured to surround at least a portion of a fluorescent lamp having plasma current passing therethrough when the fluorescent lamp is powered ON; disposing the magnetic core at least around the portion of the fluorescent lamp; and wherein when the fluorescent lamp is powered ON, plasma current of the fluorescent lamp forms a primary winding of a transformer defined by the magnetic structure and plasma current of the fluorescent lamp passing therethrough, and power is magnetically coupled from the plasma current of the fluorescent lamp to the power extraction winding of the magnetic structure for use in powering a device to be coupled thereto.
Advantageously, those skilled in the art will note from the above description that provided herein is an apparatus, lamp assembly and method that allow direct powering of a device, such as a temperature modulation component, employing at least in part plasma current of a powered fluorescent lamp. Advantageously, any powering required by the apparatus is small relative to the light output gained by the apparatus. As a further enhancement, the magnetic core of the apparatus is a ferromagnetic material chosen to have a Curie point which functions as a switching mechanism to discontinue powering of a temperature modulation component, such as a resistive heating element, at or near the optimum cold spot temperature of the fluorescent lamp. Additionally, the magnetic core can be used to generate a signal that the fluorescent lamp or ballast has failed, e.g., based on whether or not there is plasma current passing through the core. The apparatus presented can effectively facilitate maintaining a cold spot temperature, efficacy, and light output of a fluorescent lamp, such as a T5 fluorescent lamp, over a broader range of ambient temperature conditions than currently possible. The apparatus presented can be employed with any manufacturer's luminaire, and is applicable to a wide range of fluorescent lamp applications, including warehouses and other interior applications, as well as outdoor applications.
Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims.
