LED heat management
High-power LEDs generate heat just as all other light sources, resulting from the resistance to the flow of current in the semiconductor. To ensure that the nominal luminous flux and functional life are attained, the identified maximum temperature of the LEDs depletion layer must not ever be exceeded even in continuous operation. ERCO therefore places particular importance on heat management in the luminaire, ensuring that the LED modules operate below the critical temperature range in order that they produce full power output throughout their entire functional life. ERCO uses passive heat sinks, which are maintenance-free and reliable, and unlike active systems do not consume any additional energy. Their thermally optimised design minimises the drop in luminous flux, which occurs with LEDs whenever they heat up.
Heat dissipation through the housing With spotlights, the heat can be efficiently dissipated away from the LED module via the housing. The cast-aluminium material gives the luminaire good thermal conductivity and a high thermal capacity. The large-area connections between the rear of the housing and the LED´s PCB ensure good heat conduction.
Heat dissipation via cooling fins The correct design of cooling fins ensures that the recessed luminaires have an ideal thermal balance. The position, length and thickness of the cooling fins are thermally simulated in the development process to determine the optimum design for efficient heat dissipation.
Dissipation through heat sink plate In certain housing shapes, such as with Cylinder surface-mounted luminaires for the outdoor area, it can be necessary to fit an additional heat sink plate between the LED module and the luminaire housing to improve thermal coupling. Here too, the construction and dimensioning are based on thermal simulations which are part of the design process.
Thermal simulations
Thermal coupling The LED module is permanently bonded to the spotlight housing, creating ideal conditions for heat dissipation. This is one fundamental advantage of such integrated LED solutions over all other types of retrofitted designs.
Ribbed housings The cooling fins on the rear of the Powercast housing increase the surface area and enable the LED´s heat to be optimally discharged through radiation and convection.
Thermal radiation
Thermal simulations Beginning with the development phase of LED luminaires, the ERCO engineers produce thermal simulations to optimise the heat management. Tests in the measurement laboratory take place to confirm the accuracy of the detailed simulations and guarantee excellent light output when the finished product is in use.
Thermal radiation from LED luminaires In high-power LEDs, as with other lamps, heat is generated because of the flow of current. This heat is largely dissipated to the rear of the luminaire via the PCB and via the coupling to heat sinks or the luminaire housing. On the positive side, the light of white LEDs is free of infrared radiation, which means that the beam does not warm up the target object. This aspect is particularly relevant for museums as, for conservational reasons, placing a thermal load on the exhibits is undesirable. The same applies to the lighting of heat sensitive foodstuffs.
Thermal radiation from luminaires with low-voltage halogen lamps As thermal radiators, low-voltage halogen lamps generate light via a glowing filament, causing heat emission in all directions. Compared with LEDs, the electromagnetic spectrum of low-voltage halogen lamps has a higher proportion of infrared. This means that infrared filters are usually necessary for the illumination of artworks, which reduces the efficiency.
Functional life of LEDsGood heat management allows the potential of LEDs to be used at full power over their entire functional life. The depletion layer temperature, which is measured between the LED´s two conductive layers, is the critical parameter for the heat management. If this temperature rises above a critical value, the first thing to be reduced is the functional life. If the maximum value is exceeded, the LED will be completely destroyed. The possible reduction of the luminous flux to 70% and the perfect function of 50% of the LEDs are entered into the equation to calculate the nominal functional life. ERCO designs the heat management of its LED luminaires such that a functional life of 50,000 hours can be expected.
By using dedicated PCB layouts equipped with carefully selected LED binnings, ERCO ensures that optimum luminous flux and colour rendition is obtained for each specific lighting task.
The optical systems for LED lighting tools are vastly different from those of conventional luminaires. ERCO designs and builds these systems in-house to ensure a perfect match, thereby allowing their full potential to be exploited in terms of efficiency and lighting quality.
ERCO places particular importance on heat management. This ensures that LED modules operate within their safe temperature range, achieving rated life and output for the specified power throughout their operational life.
LEDs require perfectly matching electronic control gear. The development of electronic modules in-house gives ERCO freedom in designing the form and function of innovative lighting tools.
LEDs and digital lighting controls such as Light System DALI are truly made for each other. No other light source can be controlled as flexibly and efficiently as an LED. The user-friendly operation through lighting control allows great scope to design scenographic lighting in the sense of "tune the light", this enables the potential energy saving to be fully realised.
