UFC 3 -520-01
June 10, 2002
Table F -5. THD of Various Devices
Device
Typical THD
Standard electronic ballast
20% or less
Low harmonic electronic ballast
10% or less
Magnetic energy saving ballast, 2 -F40
15 20%
Magnetic energ y saving ballast, 2 -F96
25 30%
Screw-in electronic ballast compact
125 175%
fluorescent
Dimming of magnetic ballast
40 >100%
Personal computers and peripherals
100 150%
Adjustable speed drives
>100%
F-17.2
Generally, a facility will have othe r offending sources of harmonic distortion if
lighting-induced harmonic distortion creates problems. If excessive harmonic distortion
is suspected, perform power quality monitoring in accordance with Chapter 12 to
characterize the facility. Based on the results of the monitoring, determine first if the
lighting is the principal cause. For example, a small number of ASDs can easily
produce greater levels of harmonic distortion than the entire lighting system. Ensure
that monitoring also checks the neutral currents of representative circuits.
F-17.3
Harmonic distortion solutions should be addressed at the facility level. If
necessary and after confirming that lighting is the principal cause of problems, select
and install electronic ballasts and other lighting equipment of a style designed to
produce lower levels of harmonic distortion.
F-17.4
Although unrelated to harmonic distortion, the use of electronic ballasts has in
the past interfered with other electronic equipment. For example, consumer grade
remote controls and older professional remotes operate by ultrasonically modulated
modulation, when modulated at a frequency close to the modulation frequency of the
remote control device, can create an unacceptably small signal to noise ratio. The
operating frequency of most consumer remotes is around 28 to 40 kilo -Hertz. To
minimize the potential for interaction, ballasts are being designed to operate closer to
100 kilo-Hertz. Newer audio-visual systems tend to use 900 mega-Hertz or 2.4 giga-
Hertz. Although problems have been observed in the past, lighting manufacturers have
tended to correct this problem as described above. Contact the manufacturer for
guidance if additional shielding is required for especially sensitive equipment.
F-34
Previous Page
