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Power
Quality and Harmonics
Power
Quality ......What is it?
These new electronic technologies rely on the conversion of the AC supply to
DC, this process (until recently) has been very non-linear and produced high
levels of odd harmonics in the supply current.
Harmonics present in the ac supply network are not new and in the past were
mainly produced by the magnetizing current of transformers or resonance
effects. The problem now is the excessive level of certain odd harmonics
namely the 3rd, 5th, 9th, 11th etc., the worst being the 3rd. It is now known
that they are causing the overheating of neutral cables and transformers.
Power quality is an important issue for the generators and utilities because
of the cost to produce and deliver it and to the users because of the cost and
the quality of supply. The changes in the load characteristics as discussed
above together with present and future PQ standards have created an expanding
market for power quality conditioning equipment. However in order to apply
power conditioning equipment effectively users and suppliers must be able to
monitor the suspect supply, analyze the results and select the most cost
effective solution.
One important point to note in the selection of a power quality conditioner is
that the one chosen must solve the particular problem without creating new
ones. A good example of this is connecting a ferroresonant transformer to the
output of a local inferior generator to reduce voltage variations only to see
them get worse due to the generators fluctuations in supply frequency.
Claude Lyons are specialists in the manufacture of mains power control and
conditioning equipment and can provide a total Power Quality Management
solution to almost any installation be it protection of a single item of
equipment or a complete industrial site.
A typical PQM programme would comprise a site survey to identify the
categories of disturbance present followed by a complete analysis of the data
and the presentation of a complete conditioning solution based on current and
future needs.
In simple cases the installation of conditioning and harmonic products like
the Pure Power UPS or the Ferrotran ferroresonant transformer is all that is
required to solve the problem. Whereas more serious harmonic problems may
require harmonic cancellation transformers and complete active harmonic
conditioning.
The table below summarizes the different categories of power quality problems,
the possible problems causes and typical conditioning solutions.
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In
order to assist you from your critical power quality situation, we are having a
few solutions which might be suitable to restore the situation depend on it's
level.
Please
do not hesitate to contact us should you required
further assistant.
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