9
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HARMONIC DISTORTION
Series 9 and Ferro UPSs Address Harmonics
Harmonics are Everywhere
Case Study
- Electronics:
A large computer chip manufacturer
had frequent untraceable errors in
a product testing lab. This meant that
the reason a test failed could not be
confirmed or repeated. Was there
a problem with the product, or was
the test environment causing these
errors? Measurements revealed
excessive levels of harmonic
distortion in the voltage supplied to
their equipment. When the harmonic
distortion problem was treated, the
untraceable errors disappeared.
Case Study
- Broadcasting:
A broadcaster was experiencing
lock-ups of mixing boards and
program corruption of video
routers. On one occasion, during
a live broadcast, a video mixer
became inoperable resulting in the
completion of the broadcast from a
single camera position. Measurements
revealed excessive levels of harmonic
distortion in the voltage supplied to
this equipment. When the harmonic
distortion was removed the
operational problems disappeared.
There are many similar examples
where electronic equipment such
as computers, telecommunications
and broadcast equipment suffers the
consequences of harmonic distortion.
The reality is that this equipment is
sensitive to the quality of the voltage
waveform. In order to ensure the
proper operation of this equipment,
voltage must be free of distortion.
Power Consultants Warn:
• A site may not have an overload or unsafe condition now, but the owner needs to be on
guard against this harmonic threat.
Effects of Harmonics
• High levels of harmonics result in erratic or subtle malfunctions of equipment that can have
serious consequences.
• Overheating could cause overvoltage damage and premature failure to computers and
office equipment.
• High harmonic levels can fool certain control circuits into erroneous operation. CPU clock
timing operations can be falsely triggered.
• Intermittent electrical noise is intense enough to corrupt digital signals and cause
malfunctions.
• Distortion of voltage is severe enough to impair ride-through capabilities of computers and
related equipment.
Competitor Response
• Harmonic voltages have virtually no effect on modern computers, but can cause
overheating in some cases.
• The UPS may operate in backup mode much more often than usual due to the poor quality of
the AC power source (source with severe line voltage distortion).
Independent Evaluation of Competitor Series 5 UPS
• The APC Smart-UPS
®
momentarily transfers to inverter for almost any voltage anomaly.
• UPS equipment worked properly with harmonic distortion levels below 5% THD. As distortion
levels increased, more interaction was noted. At 8.66% THD, the competitor UPS would not
operate from the test voltage until the sensitivity switch on the back of the unit was set to a more
tolerant position.
What Does It Mean?
1. Harmonics will cause sensitive equipment to crash and fail prematurely.
2. Line-interactive technology may not protect the sensitive equipment from harmonics.
3. Online and Ferro UPSs are recommended to protect sensitive equipment from harmonics.
