In the Heat of the Light: LED lights and sustained exposure to extreme conditions
Rico Schulz, Product Manager Lighting Technology at explosion protection expert R. STAHL, discusses about impact of extreme temperature on LED Lighting.
Mr Schulz, LED lights are commonly regarded as particularly vulnerable to high temperatures. How much heat is too much for these devices?
Since LED are semiconductor devices, the various temperature-dependent parameters to consider include forward voltage, wavelength and light output. It is not so much the lifespan of the LEDs themselves that is compromised, but rather the integrated control electronics. However, thanks to optimised control electronics, high-end products like our 6036 series LED tubular light fittings now easily handles temperatures up to +60 °C.
How much of a role does the ambient temperature play?
Depending on the type of application, LED fittings can of course be exposed to relevant environmental temperatures – for instance, in machine and systems engineering when they are installed in generators. Such luminaires therefore require a particularly heat-resistant design. For operation in such locations, the housing materials and gaskets must be designed to permanently withstand intense heat and especially extreme temperature fluctuations.
Are thermal issues taken into account for enclosure construction?
LED Lights require heat to be dissipated on the outside as quickly as possible. However, since air is a poor conductor of heat, the enclosures for these products should be designed as compact as possible to minimise the volume of air. This is the idea behind the development of our LED tubular lights.
How can intelligent power electronics reduce temperature stress?
Fine tuning between LED light sources and electronics is crucial to find the optimal balance between performance, lifespan and thermal stress. Even the most intelligent electronics cannot completely prevent thermal leakage power. Using sensor input, however, they can respond to system temperature and reduce power consumption to ensure the designated lifespan of the system is not compromised.. Our new 6125 and 6525 series LED floodlights are a good example.
Speaking of cooling: do LED lights ever get "cold feet", too?
In principle, LEDs like it cold – moderately cold, that is. At very low temperatures below -50 or -55 °C, which can occur in Arctic regions, the luminaires are exposed to high levels of mechanical stress as they heat up in operation. This is detrimental to frost-sensitive components. EMC protection also suffers. For this reason, luminaires for such operating conditions also require a special design that mitigates the temperature difference, e.g. via intelligent circuitry.
How do you test and rate temperature susceptibility?
Besides consulting temperature resistance calculations, we perform various stress tests together with our partner companies. For instance, in order to determine vulnerabilities and exposure limits as early as possible during product development, we subject our equipment to an accelerated ageing process in accordance with HALT (Highly Accelerated Lifetime Test) provisions. As part of this procedure, the luminaires are exposed to rapid temperature changes and vibrations in a climatic test chamber.
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