Technical
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Lighting Council Australia Official News
No. 11
11
No.
Power Factor - Reducing power bills with
informed luminaire selection
The cost of lighting a space does not end once installation is complete and the switch has been 'flicked on'. The ongoing costs
of electrical supply for lighting can be substantial, particularly in complex buildings that require numerous luminaires or open
spaces with high power floodlights. Fluorescent and high intensity discharge (HID) lamp circuits have an inherently low power
factor (usually around 0.4 to 0.5) due to control gear inductance. Uncorrected or low power factor (LPF) light fittings result in
higher currents consumed by the luminaire and a reduced numer of fittings able to be installed on the lighting circuit. As a result
of low power factor the kVA is increased more than it needs to be. Reducing the kVA usage and bringing the power factor closer
to unitity (1) lowers the energy bills as well as allowing better utilisation of luminaires installed on the lighting circuit. Low power
factor and unexpected increased current can cause problems. Choosing lighting with a good 'power factor' will help reduce energy
costs and improve the quality of lighting.
What is Power Factor?
Power factor is essentially a measure of how effectively electrical
power is being used by a light circuit. Power factor is represented
by a number between 0 and 1. The higher the number, the more
efficiently the circuit uses electricity.
The common wire wound ballast is a
ferro-magnetic component that alters the
phase relationship between voltage and
current. This altered relationship is known as
'power factor' and can cause wasted power
and increased running costs.
"HPF lighting
should be used
in areas where a
high number of
Can low power factor be corrected?
luminaires are
Specification, purchase and use of high power factor products is
required." Yes.
the best route to power factor improvement. Capacitors or electronic
Power factor is calculated as the ratio of real
power (that which makes the light operate)
divided by apparent power (Volts x Amps).
The two types of power are often represented
by a right-angle triangle. The apparent power
is the combination of active and reactive (that
which energises the electromagnetic field and does no
operational work) power that is needed for a circuit to operate.
VA (apparent power)
In extreme circumstances, this can cause circuit breakers to trip or
perhaps worse. This mistake can also cause low voltage conditions,
resulting in the dimming of lights, which can lead to subsequent
quality and safety concerns. Low power factor light fittings require
more current to perform the same operation as
high power factor fittings. Some energy suppliers
in NSW, Victoria, Tasmania and WA charge
commercial customers on the basis of kilovolt
amps (kVa) as well as kilowatt hours (kWh). This
means low power factor lighting will cost more to
run as the same light equipped with high power
factor correction capacitators or electronic ballasts.
VARs
(reactive
power)
ballasts can improve individual luminaires. If capacitors are to be
added to an existing luminaire the manufacturer should be consulted.
Incorrect installation near hot components such as lamps or ballasts
may quickly jeopardise the expected improvement or cause a hazard.
There may also be a need to add blocking inductors in areas where
ripple frequency load control is used. Large installations may require
automatic correction capacitor banks to meet supply utility
requirements (usually a power factor of 0.9). These utilities often
insist on high power factor lighting especially where a large number
of luminaires are installed.
0
Labelling Requirements
Watts (real or active power)
What problems can low power factor cause?
Lower power factor fluorescent HID lamp circuits require more
current than is necessary to do required work than with improved or
high power factor (HPF) fittings. While low power factor (LPF)
operation is not usually a problem in residential homes with a few
fluorescent luminaires, it can create significant problems where large
numbers of luminaires are in use. If the installation designers have
not allowed for the higher current required with LPF operation,
excess cable losses and heating results, which can damage or
shorten the life of installation.
AS/NZS60598.1 'Luminaires' - Section 3: 'Marking' outlines the
marking requirements for power factor. While the standard does not
indicate a requirement to have the power factor labelled on light
fittings, it is common industry practice to include this or LPF/HPF to
reduce the likelihood of design mistakes.
For more information on power factor and reducing energy
consumption, please contact your power supplier or qualified energy
consultant.
The information in this newsletter has been prepared in good faith by Lighting Council Australia. However:
- The information is not intended to constitute advice and persons should seek professional advice before relying on the information.
- Lighting Council Australia does not warrant the accuracy of the information, and to the extent permitted by law, disclaims responsibility for
any loss or damage of any nature whatsoever which may be suffered by any person directly or indirectly through relying upon it, whether
that loss or damage is caused by any fault or negligence of Lighting Council Australia or otherwise.
For more details please contact:
Lighting Council Australia
Tel
+61 2 6247 8011
Fax +61 2 6247 9840
email info@lightingcouncil.com
Web www.lightingcouncil.com