Power Factor Controller.
Power Factor Definition : Power factor is the ratio between
the KW and the KVA drawn by an electrical load where the KW is the actual
load power and the KVA is the apparent load power. It is a measure of
how effectively the current is being converted into useful work output
and more particularly is a good indicator of the effect of the load current
on the efficiency of the supply system.
The Power factor of the total current supplied to the distribution
board is monitored by a controller which then switches capacitor banks
In a fashion to maintain a power factor better than a preset limit. (Typically
0.95) Ideally, the power factor should be as close to unity as possible.
There is no problem with bulk correction operating at unity, however correction
should not be applied to an unloaded or lightly loaded transformer. If
correction is applied to an unloaded transformer, you create a high Q
resonant circuit between the leakage reactance of the transformer and
the capacitors and high voltages can result.
Power Factor Controllers
Power factor controlers are typically panel mount and used
like a panel mount meter, indicating the power factor at the point of
supply. Power factor controllers are programmable and range from quite
simple to very complex.
A good configuration is to use at least two small steps and at least four large steps. For large installations, up to 14 stages can be used.
The number of times that a bank can be switched is limited with delay ON and delay OFF times that are programmable. Some controllers keep the numbers of operations equal across all banks. There are a number of other options that can be included such as harmonic current alarms and low current thresholds to prevent capacitors being connected under very light load.
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