Philips Electromagnetic Lamp Ambient and operating temperatures, Gear, a Ballasts, b Starters

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3.12 Ambient and operating temperatures

2) Gear

a) Ballasts

The main ballast temperature parameters tw (maximum permissible coil temperature) and Δt (coil temperature rise in standard test) are described in section 5.1.6. Ballasts are normally mounted directly inside a luminaire.The actual ballast coil temperature in practice depends on the cooling properties of the ballast surroundings, e.g. material of mounting surface, type of fixing, standing air or ventilation. For that reason it is impossible to predict the actual ballast coil temperature without doing a temperature test in practical circumstances. Of course a ballast normally will be cooler when it has lower losses and/or a lower Δt value and/or larger dimensions.

Connections to a ballast are in many cases made by means of a terminal block.These terminal blocks have their own temperature limits, usually 100 to 120 ºC, which should not be exceeded.

b) Starters

Since they incorporate semi-conductors and capacitors, electronic starters have a maximum permissible temperature.This value is marked on the starter and is usually 80 or 90 ºC. In most applications the starter case temperature will not exceed this limit, as the starters hardly produce heat by themselves.

But if the starter is incorporated in the luminaire or placed near the hot ballast, its temperature can rise considerably. It is advisable to mount the starter on the coolest spot possible.

c) Capacitors

Capacitors have a maximum permissible temperature, which is marked on the case and is usually 85 or 100 ºC.Above this temperature they can break down or lose capacitance.They hardly produce heat by themselves and must be placed away from the hot ballast.Additional temperature measures are advisable when the capacitor case temperature is unknown and can be critical.

3) Luminaires

Professional luminaires are, like ballasts, designed and constructed to have (under standard conditions) an average lifetime of at least 10 years in continuous operation with the appropriate (maximum) lamp type. The volume of the luminaire, the choice of materials, the cooling properties, etc., are chosen in such a way that, at an ambient temperature of 25 ºC in indoor applications, no part of the luminaire exceeds its maximum specified temperature. In practice this ambient temperature limit is sufficient to cope with most applications and non-nominal circumstances, as long as the latter are within the specifications. In cases where the ambient temperature is (temporarily) higher than 30 ºC, the most critical part of the luminaire may exceed its maximum specified temperature.This, of course, shortens lifetime, but to what extent is in general hard to say. It depends on the part in question (e.g. luminaire housing, mirror optics, cabling, lamp tube, lamp base, etc.).

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