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2) Gear
a) Ballasts
The main ballast temperature parameters t
w
(maximum permissible
coil temperature) and ∆t (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 ∆t 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.).
5
135
3.12 Ambient and operating temperatures