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Metallized polypropylene film capacitors for power factor correction - low voltage
OBSERVATIONS ON POWER FACTOR CORRECTION
It is known in electrotechnique that there are fundamentally
two types of loadings. Active loadings that generate work
and are the resistive loadings. The second type is
represented by the reactive loadings; such as inductances
and capacitors.
From a practical stand-point, in production lines, the biggest
part of the loadings is of the inductive type and is represented
by electrical motors, transformers, rectifiers etc. The reactive
current (inductive in this case) is only meant to create the
magnetic field but does not produce work.
With a view to energy transmission, this inductive current
generates voltage lowerings that are expressed in losses of
active power on the lines.
The inductive reactive current constitutes a further loading
for generators, transformers, transportation and distribution
lines.
The index that defines the power consumption of magnetic
current in delay on the voltage is the power factor cosφ. It is
determined by the ratio between active power and apparent
power.
With a completely resistive loading, the active power and
the apparent power are the same thus the cosφ is 1.
Under conditions of inductive loading, the ratio between
active power and apparent power will be lower than 1.
The lower the cosφ, the higher the absorbed inductive
current.
Therefore, a plant working with a low cosφ has
the following disadvantages:
 higher losses of power in transmission in the electrical lines
higher voltage lowerings
higher dimensioning of the generation, transportation, transformation and utilization plants
Last but not least, for a low cosφ the companies producing
and distributing electrical energy
charge - by law - considerable money penalties
and sanctions.
As a consequence, the energy utilized by the users is lower
than that generated by the energy supplier.
It is evident that these negative consequences - in a situation
of increasing need of energy - are not tolerable in presence
of a massive energy saving plan and major performances,
both from the point of view of the energy distributor and
that of the user. It is therefore important to eliminate or, at
least, to reduce the consequences of a low power factor with
devices whose behaviour can be compared to a generator
of capacitive reactive power as opposed to the phase that is
given to the loadings.
The capacitors are devices suitable to achieve this purpose.
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