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Here is an example. A steel stamping operation runs at
100 kW (Working Power) and the Apparent Power meter records
125 kVA. To find the PF, divide 100 kW by 125 kVA to yield
a PF of 80%. This means that only 80% of the incoming
current does useful work and 20% is wasted through heating
up the conductors. Because Laurens Electric must supply
both the kW and kVA needs of all customers, the higher
the PF is, the more efficient our distribution system
becomes.
Improving the PF can maximize current-carrying capacity,
improve voltage to equipment, reduce power losses, and
lower electric bills.
The simplest way to improve power factor is to add PF
correction capacitors to the electrical system. PF correction
capacitors act as reactive current generators. They help
offset the non-working power used by inductive loads,
thereby improving the power factor. The interaction between
PF capacitors and specialized equipment, such as variable
speed drives, requires a well designed system.
PF correction capacitors can switch on every day when
the inductive equipment starts. Switching a capacitor
on can produce a very brief over-voltage condition.
If a customer has problems with variable speed drives
turning themselves off due to over-voltage
at roughly the same time every day, investigate the switching
control sequence. If a customer complains about fuses
blowing on some but not all, of their capacitors, check
for harmonic currents.
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