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Mid-1970s Philips SN/T 250W BU
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The SN/T 250W BU is an experimental lamp that was developed during the 1970s for professional lighting applications that require a good light color quality, such as in shop and retail settings. A tin halide fill chemistry was chosen because of its broadband molecular spectrum which covers the whole visible domain, resulting in a high CRI of at least 80 Ra8. The lamp’s chemistry is balanced for the production of warm-white light light with a CCT around 3000 K, adjusted with lithium and indium additives.
The nature of the thermal molecular plasma operating in tin halide vapor results in a very constricted arc that can be subjected to convection instabilities. In order to ensure a stable lamp operation, Philips opted for a compact burner design featuring a relatively short electrode gap length of 12 mm only. Moreover, because the lamp was intended for a use in downlighting applications, the burner is shaped with an asymmetric isothermal profile which ensures a high cold spot temperature and stable (vertical) convection currents.
The SN/T 250W BU was designed for an operation on 250 W mercury lamp ballasts provided with an ignitor. Because of its constricted arc the lamp’s power factor is 0.64 only, which limits the dissipated power to 190 W although the rms current and voltage are very close to those of 250 W mercury lamps. This, combined with the high infrared output of the tin halide discharge, result in a light output flux of around 11 klm, which is actually lower than that of fluorescent mercury lamps.
Although Philips was very active in the development of tin halide lamps during the 1960s and 70s, it never released the SN/T on the market. Reasons for that are the low efficacy intrinsic to the tin halide fill chemistry, and limitations related to the lamp's electrical properties (i.e., too high re-ignition voltage peak). The Dutch eventually chose to concentrate their efforts on the NTI salt system (i.e., sodium-thallium-indium) which enables significantly higher lamp efficacies (70–80 vs. 60 lm/W) at the cost of a lower light color quality (65 vs. ~80 Ra8).
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The SN/T 250W BU is an experimental lamp that was developed during the 1970s for professional lighting applications that require a good light color quality, such as in shop and retail settings. A tin halide fill chemistry was chosen because of its broadband molecular spectrum which covers the whole visible domain, resulting in a high CRI of at least 80 Ra8. The lamp’s chemistry is balanced for the production of warm-white light light with a CCT around 3000 K, adjusted with lithium and indium additives.
The nature of the thermal molecular plasma operating in tin halide vapor results in a very constricted arc that can be subjected to convection instabilities. In order to ensure a stable lamp operation, Philips opted for a compact burner design featuring a relatively short electrode gap length of 12 mm only. Moreover, because the lamp was intended for a use in downlighting applications, the burner is shaped with an asymmetric isothermal profile which ensures a high cold spot temperature and stable (vertical) convection currents.
[img]https://i.ibb.co/CPnRDQF/Philips-SN-T-250-W-BU-NL-m1970s-b.jpg[/img]
The SN/T 250W BU was designed for an operation on 250 W mercury lamp ballasts provided with an ignitor. Because of its constricted arc the lamp’s power factor is 0.64 only, which limits the dissipated power to 190 W although the rms current and voltage are very close to those of 250 W mercury lamps. This, combined with the high infrared output of the tin halide discharge, result in a light output flux of around 11 klm, which is actually lower than that of fluorescent mercury lamps.
Although Philips was very active in the development of tin halide lamps during the 1960s and 70s, it never released the SN/T on the market. Reasons for that are the low efficacy intrinsic to the tin halide fill chemistry, and limitations related to the lamp's electrical properties (i.e., too high re-ignition voltage peak). The Dutch eventually chose to concentrate their efforts on the NTI salt system (i.e., sodium-thallium-indium) which enables significantly higher lamp efficacies (70–80 vs. 60 lm/W) at the cost of a lower light color quality (65 vs. ~80 Ra8).
Keywords: Lamps](images/image.gif?id=1399909797460 "Click to view full size image
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Mid-1970s Philips SN/T 250W BU
The SN/T 250W BU is an experimental lamp that was developed during the 1970s for professional lighting applications that require a good light color quality, such as in shop and retail settings. A tin halide fill chemistry was chosen because of its broadband molecular spectrum which covers the whole visible domain, resulting in a high CRI of at least 80 Ra8. The lamp’s chemistry is balanced for the production of warm-white light light with a CCT around 3000 K, adjusted with lithium and indium additives.
The nature of the thermal molecular plasma operating in tin halide vapor results in a very constricted arc that can be subjected to convection instabilities. In order to ensure a stable lamp operation, Philips opted for a compact burner design featuring a relatively short electrode gap length of 12 mm only. Moreover, because the lamp was intended for a use in downlighting applications, the burner is shaped with an asymmetric isothermal profile which ensures a high cold spot temperature and stable (vertical) convection currents.
[img]https://i.ibb.co/CPnRDQF/Philips-SN-T-250-W-BU-NL-m1970s-b.jpg[/img]
The SN/T 250W BU was designed for an operation on 250 W mercury lamp ballasts provided with an ignitor. Because of its constricted arc the lamp’s power factor is 0.64 only, which limits the dissipated power to 190 W although the rms current and voltage are very close to those of 250 W mercury lamps. This, combined with the high infrared output of the tin halide discharge, result in a light output flux of around 11 klm, which is actually lower than that of fluorescent mercury lamps.
Although Philips was very active in the development of tin halide lamps during the 1960s and 70s, it never released the SN/T on the market. Reasons for that are the low efficacy intrinsic to the tin halide fill chemistry, and limitations related to the lamp's electrical properties (i.e., too high re-ignition voltage peak). The Dutch eventually chose to concentrate their efforts on the NTI salt system (i.e., sodium-thallium-indium) which enables significantly higher lamp efficacies (70–80 vs. 60 lm/W) at the cost of a lower light color quality (65 vs. ~80 Ra8).
Keywords: Lamps")
