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LED Modules


LED lighting has the potential to be more energy efficient than any other known lighting technology. But, two aspects of energy efficiency are important to consider: the efficiency of the LED device itself (source efficacy) and how well the device and fixture work together in providing the necessary lighting (luminaire efficacy). How much electricity is consumed depends not only on the LED device, but also on the lighting fixture design. Because they are sensitive to thermal and electrical conditions, LEDs must be carefully integrated into lighting fixtures. The efficiency of a poorly designed fixture that uses even the best LEDs will be only a fraction of what it would be if the fixture were well-designed, and the design can also affect lumen maintenance.
Key aspects of high-quality light are the color appearance of the light itself, which is described by its color coordinates but is often condensed (with significant loss of information) to correlated color temperature (CCT), and how the light affects the color appearance of objects, which is referred to as color fidelity. Color fidelity can be quantified using the color rendering index (CRI), or with one of several other recently developed metrics. LED light sources have demonstrated that they can achieve a wide range of color qualities, depending on the demands of the lighting application.
However, to achieve high levels of color quality, there are typically cost and efficiency tradeoffs. In general, a minimum CRI of 80 is recommended for interior lighting, and LED products can readily achieve this performance. CRI of 90 or higher indicates excellent color fidelity; LEDs can also meet this threshold. 

WHAT IS LM-80?

The LM-80 is one such standard. LM-80 refers to a method for measuring the lumen depreciation of solid-state lighting sources, such as LED packages, modules and arrays. Before the advent of LM-80, LED component manufacturers each reported lumen maintenance data using their own disparate and varied systems. To avoid customer confusion, members of the Illuminating Engineering Society (IES), including members from Philips Lumileds, came together to create a standard methodology that would allow customers to evaluate and compare the lumen maintenance of LED components from different companies. LM-80 was born.
LM-80 can be a useful tool for lighting professionals who are looking to analyze LED products; however, it is not a measure of LED system performance or reliability. It only describes how to measure how one part of an LED luminaire—the LED light source—performs over a period of time and under certain set conditions. Other components, including the LED optical system, heat sink, LED drivers and luminaire housing, should also be taken into consideration to form a full picture of an LED luminaire’s projected useable life. LM-80 is merely one critical part of a larger puzzle. LM-80 is also not a measure of the “lifetime” of a component or the LED lamps and luminaires that use that component. Unfortunately, LED component, lamp and luminaire manufacturers, among others, often use the data found in an LM-80 report to substantiate the “lifetime” claims of an LED product, even though that data alone cannot be used to predict the useful life of an LED product or system.

WHAT LM-80 CAN DO FOR YOU

While LM-80 doesn’t provide a full picture of a LED component’s long-term performance, it is an important part of the equation. Luminaire and lamp manufacturers, lighting designers and researchers should know how quickly the light output of an LED will depreciate to help them determine the useful lifetime of the product in which the LED will be used. They should also look at how the LED’s light output has degraded under the various temperature and current conditions, as well as how the color point has shifted at those same conditions.

What is the LM-79 test methodology?

LM-79 prescribes the testing procedures and precautions including lab considerations, ambient conditions, electrical equipment and measurement equipment used for carrying out LED products testing. It specifies three test methods to perform the measurements as well as proper treatment and operating orientation of the luminaires being measured.

Why do we need it?

Due to the variety of LED products available in the market, there is a need to assess the quality and various parameters associated with lighting products. LM-79 data enables objective product comparisons and allows for evaluation relative to performance requirements. How is LM-79 different from other test methods used for conventional lighting products? Due to the unique thermal and electrical characteristics of LEDs, standard test methods using relative photometry, cannot measure the lumen output of LED light sources. The LM-79 test remedies this problem by using absolute photometry.

What is relative photometry?

Relative photometry is used for testing standard filament or fluorescent lamps. Lamps and ballasts are tested separately from luminaires. The final output is the luminaire efficiency, calculated by dividing the total lumen output of the luminaire by the product of the rated output of the lamps and the ballast factor.
Relative photometry reduces the volume of luminaire tests, as they specifies can mimic lamp data from existing tests.

What is absolute photometry?

Absolute photometry is used to directly measure the total lumen output of complete lighting systems including lamp, ballast, driver, thermal management and all other fixture components. The efficiency of an integrated LED luminaire cannot be calculated in a standard manner. Instead luminous efficacy is calculated by dividing the total light output produced by total input electrical power.

What are the LM-79 test outcomes?

IESNA prescribes the following uniform parameters to present the data obtained during LM-79 testing.


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