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Technical
233
Glossary of terms
Dimmability
The Sylvania lamps range includes dimmable LEDs lamps. Most conventional dimmers
have been designed for incandescent lamps and are therefore rated for higher
minimum loads (W) than LED lamps consume. There may therefore be some restrictions
in terms of functionality of dimmers with individual LEDs – but when more than one
lamp is used to increase the total loading, dimming becomes easier.
Downward Flux Fraction (DFF)
The factor of the total LOR, which is downward, taking the combined ULOR and DLOR
as 100%. Using Cassini as an example, the DLOR is 37% and the ULOR is 15% so the
combined is 52%. If this is taken as 100% LOR, 72% is downward (37% divided by
53%).
Drivers
Electronic devices that transform the high mains voltage into a constant current lower
voltage for operating the LEDs. A miniature electronic driver is contained inside the base
of each Sylvania LED lamp.
Glare
Glare is the discomfort caused by high luminances in the field of vision.
Heat Sink
A device used to conduct heat away from the LED sources and dissipate it to the
surrounding air. The more efficiently an LED is cooled the greater its efficacy, light
output and lifetime. Materials having excellent thermal properties and optimised
cooling fin geometries are engineered into Havells-Sylvania lamps and luminaires to
deliver the pinnacle of performance.
Infrared (IR) Radiation
Comprises electromagnetic waves in the spectral range between visible light and
microwaves, which produce a heating effect when absorbed by materials. All lamps and
luminaires produce infrared radiation, but the quantity emitted by LEDs is far lower than
other technologies and this makes them ideal for reducing air conditioning load, as well
as for the illumination of heat-sensitive goods.
Illuminance
This definition determines the amount of light that covers a surface. If Ø is the luminous
flux and S is the area of the given surface then the illuminance E is determined by
E=Ø/S. The unit of illumination in SI system is lx, and in foot-pound system it is foot-
candle. One lx is the illuminance of 1 m² surface area uniformly lighted by 1 lm of
luminous flux.
Junction Temperature (Tj)
The temperature of the Junction of the LED die inside the LED lamp. Measuring the
LED die temperature by direct mechanical means is difficult and may lead to erroneous
results. It is recommended that the Tj is calculated with manufacturer’s data through
measurement of the temperature at the solder point (Tsp).
LED (Light Emitting Diode)
An electronic semiconductor component which emits light when an electrical current
flows through it. The colour of light emitted depends on the chemical doping of the
semiconductor material.
Lens
An optical component having two refractive surfaces, at least one of which is either
convex or concave. In LED lamps the function of a lens is to focus or disperse the light
rays to achieve the desired beam angle or light distribution pattern.
Lifetime
LED lamps can have extremely long lives, however their light output diminshes as they
age. They can carry on working until they are emitting less than 10% of their initial light
output, but with so little light left they would be practically useless. Sylvania defines the
lifetime of its LED lamps the same way as for other lamps: i.e. the burning hours until
the light output has decreased to 70% of the initial value, or when 50% of a group
of lamps will have failed – whichever is the soonest. The International Electrotechnical
Commission (IEC) is currently preparing an international standard based on similar
threshold values.
Light
Light Electromagnetic radiation with a wavelength between 380-780nm. Ultraviolet
light has a wavelength of less than 380nm whilst infrared light’s is greater than 720nm.
Lighting level
The incidence of light flux on a surface per unit of area, measured in lux. There is a
difference between the vertical and horizontal lighting level.
Light output ratio (LOR)
The ratio of the luminaire light output to lamp light output. The efficiency of the
luminaire.
Lumen (lm)
Unit of luminous flux used to describe a quantity of light emitted by a source or
received by a surface.
Lumen Maintenance
Rated Lumen Maintenance Life (Lxx): The elapsed operating time over which the LED
light source will the percentage, xx, of its initial light output.
•
L80 = Time to 80% lumen maintenance, in hours
•
L70 = Time to 70% lumen maintenance, in hours
For LED lamps and luminaires, lumen maintenance is often shown as curves of relative
lumen output over time for the LED under various operating conditions, such as drive
current and junction temperature.
Luminance
The measure of brightness with which the eye perceives an illuminated surface from
a certain direction. The luminous intensity per unit of visible surface of a light source
(direct) or an illuminated surface (reflection). Luminance is indicated in candelas per
square metre (cd/m2).
Luminous efficacy (lm/w)
Indicates how efficiently a light source converts electrical energy to light.
Luminous flux (lm)
The total light output of a light source measured in lumens.
Luminous intensity (cd)
The power of a source or illuminated surface to emit light in a particular direction,
measured in candelas.
Lux (lux)
The unit of illuminance, equal to one lumen per square metre (lm/m
2
).
700
380
10000
6000
Tc(ºK)
4000
3000 2500
2000 1500
460
470
480
490
0.7
0.6
0.5
Y
X
X
X
Y
0.4
0.3
0.2
0.1
0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
0.30
0.35
0.40
0.45
0.50
0.30
0.35
0.40
2700K
BB Locus
3000K
3500K
4000K
4500K
5000K
5700K
6500K
+ Special Colours = Ra14
General Colours Ra8
+ Special Colours = Ra14
MacAdam ellipses 3
Hours
Relative Light Output at Tj
/ 5 / 7 SDCM
ex. 3000K
L80
L70
0.43
0.41
0.42
0.40
0.39
0.38
100%
90%
80%
70%
60%
50%
0
10K 20K
3.2
3.25
18.5
22
XX
XX
11
17.5
1.6
30K 40K 50K 60K 70K
0.41
0.42
0.43
0.44
0.45
0.46
Black Body Locus
2870K
3220K
3045K +/
-
135K
（
5SDCM
）
3045K +/
-
175K
（
7SDCM
）
Chromaticity range of ANSI C78.377 (3000K)
3045K +/
-
70 K
（
3SDCM
）
14 Ø
11 Ø
Anode
Cathode
1A (Ra>90)
1B (90>Ra>80)
2A (80>Ra>70)
2B (70>Ra>60)
3 (60>Ra>40)
4 (40>Ra>20)
Typical application
Accurate
Medical examination, colour
printing inspection, art galleries
Good
Retail, showrooms, restaurants
o ces etc
Mod rate
O ces, classrooms, security lighting
supermarkets, manual areas etc
Poor
Street lighting, parking areas etc
Not important
Street lighting
100
90
80
60
40
20