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Ballasts
What is a Ballast?
A ballast is a coil of copper wire wound around a laminated iron
former. A coil wound in this way has an electrical property called
inductance. An inductance creates a resistance to the flow of alternating
current and is used in a fluorescent fitting to control the current
flowing through the lamp. Therefore each lamp must be operated with
the appropriate ballast.
The ballast also (in conjunction with the starter)
creates a voltage spike at start-up, to get the lamp going.
Why do Ballasts Hum?
Most ballasts make a slight noise when operating. This noise is
created by the laminations of the coil former vibrating slightly
in sympathy with the 50 Hz mains. If a ballast is not constructed
properly the laminations may be loose and the noise will be louder.
Ballast noise can be aggravated by mounting the
fitting on a surface that acts as a sounding board, and by higher
than normal mains voltage.
Low Loss Ballasts
A standard ballast consumes 9 Watts of power when operating a 36
Watt lamp. This is wasted energy as it just creates heat. A low
loss ballast (available as an option on all ndLIGHT fittings)
consumes 5 Watts per 36 Watt lamp and therefore produces less heat.
In a large installation over a long period of time, the additional
cost of low loss ballasts will be more than paid for by reduced
electricity bills (from less power consumed by the fluorescent fitting
and lower running costs of the air conditioning system). Most fittings
in the ndLIGHT range can be fitted with low loss ballasts to special
order.
Electronic Ballasts
These are available as an option on most ndLIGHT fluorescent fittings.
Electronic ballasts have three main features that
make them very desirable.
1 - High Frequency Operation
Standard and low loss ballasts operate the lamp at the mains frequency
of 50Hz. This means that the lamp produces light as the voltage
goes positive, and again as it goes negative. However there is no
light produced by the lamp as the mains voltage goes through the
zero crossing region. This short cut-off time at 100Hz can be noticed
by the eye and is called 50Hz flicker. Flicker is one of the reasons
that people find fluorescent lighting uncomfortable. An electronic
ballast operates at above 20,000Hz which puts the flicker rate at
over 40,000Hz, which is far beyond the perception of the eye.
2 - Lower Energy Losses in the Ballast
The wasted energy in an electronic ballast operating with a 36 Watt
lamp is 4 Watts compared to 9 Watts for a standard ballast.
3 - Some electronic ballasts can be dimmed from
100% light output down to 1%.
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