LLE LED Downlight 3x10W WW

Posted by Marcel van der Steen in Led lights, Light measurements No Comments»

presents a measurement set of one big downlighter, equipped with three high power leds each of them consuming 10 W. Behind each led a big heatsink is mounted. In this article the measurement data can be found as well as in Eulumdat format.
See this overview for a comparison with other light bulbs.

Summary measurement data

parameter meas. result remark
Color temperature 2634 K Warm white
Luminous intensity Iv 291 Cd
Beam angle 120 deg A wide beam.
Power P 30.4 W
Power Factor 0.59 For every 1 kWh net power consumed, there has been 1.4 kVAhr for reactive power.
Luminous flux 875 lm
Luminous efficacy 29 lm/W
CRI_Ra 73 Color Rendering Index.
Coordinates chromaticity diagram x=0.4598 and y=0.4017
Fitting 230V
D x H external dimensions 240 x 100 mm External dimensions of the downlighter.
D dimension luminous area 90 mm Dimensions of the luminous area (used in Eulumdat file). Here the matte part of the glass is used.
General remarks The ambient temperature during the whole set of measurements was 20.0 deg C.

Warm up effect: the illuminance decreases with < 10 % during the warm up, which is a small effect.

Voltage dependency: consumed power and illuminance are independent from the light bulb voltage

For the eulumdat file follow this link.

Eulumdat lichtdiagram

With this article an eulumdat file is added. This is a file that a.o. indicates the radiation pattern around the light bulb. There are more parameters in the file, and these all can be read with help of the free open source program Qlumedit.

An interesting graph is the light diagram, indicating the intensity in the C0-C180 and the C90-C270 plane.

The light diagram giving the radiation pattern in the C0-C180 and C90-C270 planes.
As the light is symmetrical over z-axis, there is no difference between the lightdiagram for the two planes C0-C180 and the C90-C270.

Illuminance Ev at 1 m distance, or luminous intensity Iv

Herewith the plot of the averaged luminous intensity Iv as a function of the inclination angle with the light bulb.

The radiation pattern of the light bulb.

This radiation pattern shows a wide beam.

These averaged values are used (later) to compute the lumen output.

The intensity measurements (of each turn angle) as function of inclination angle.

This plot shows per inclination angle the intensity measurement results for each turn angle at that inclination angle.

When using the average values per inclination angle, the beam angle can be computed, being 120 degrees.

Luminous flux

With the averaged illuminance data at 1 m distance, taken from the graph showing the averaged radiation pattern,it is possible to compute the luminous flux.

The result of this computation for this lamp is a luminous flux of 875 lm.

Luminous efficacy

The luminous flux being 875 lm, and the power of the lightbulb being 30.4 W, yields a luminous efficacy of 29 lm/W.

A power factor of 0.59 means that for every 1 kWh net power consumed, a reactive component of 1.4 kVAr was needed.

Light bulb voltage 230 V
Light bulb current 225 mA
Power P 30.4 W
Apparent power S 51.8 VA
Power factor 0.59

Color temperature and Spectral power distribution

The spectral power distribution of this light bulb.

The measured color temperature is about 2650 K, being warm white.

Chromaticity diagram

The chromaticity space and the position of the lamp’s color coordinates in it.

The light coming from this lamp is close to the Planckian Locus (the black path in the graph).

Its coordinates are x=0.4598 and y=0.4017.

Color Rendering Index (CRI) or also Ra

Herewith the image showing the CRI as well as how well different colors are represented (rendered). The higher the number, the better the resemblance with the color when a black body radiator would have been used (the sun, or an incandescent lamp).

Each color has an index Rx, and the first 8 indexes (R1 .. R8) are averaged to compute the Ra which is equivalent to the CRI.

CRI of the light of this lightbulb.

The value of 73 is lower than 80 which is considered a minimum value for indoor usage.

Note: the chromaticity difference is 0.0033 indicates the distance to the Planckian Locus. Its value is lower than 0.0054, which means that the calculated CRI result is meaningful.

Voltage dependency

The dependency of a number of lamp parameters on the lamp voltage is determined. For this, the lamp voltage has been varied and its effect on the following lamp parameters measured: illuminance E_v [lx], color temperature CT or correlated color temperature CCT [K], the lamppower P [W] and the luminous efficacy [lm/W].


Lamp voltage dependencies of certain light bulb parameters, where the value at 230 V is taken as 100 %.

The power consumed and the illuminance measurements do not depend on the light bulb voltage applied.

To check whether this dependency can lead to visible changes in illuminance for possible grid voltage changes, it is noted what variations occur when the lamp voltage varies around 230 V + and – 5 V. Then the illuminance varies 0 % so no differences seen.

Warm up effects

After switch on of a cold lamp, the effect of heating up of the lamp is measured on illuminance E_v [lx], color temperature CT or correlated color temperature CCT [K], the lamppower P [W] and the luminous efficacy [lm/W].

Effect of warming up on different light bulb parameters. At top the 100 % level is put at begin, and at bottom at the end.

No noticeable effects seen. The illuminance decreases about 7 % during the warm up period that takes 1 hour. This effect is small and hence there is no meaningful warm up period.

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