Power Factor





KW is Working Power (also called Actual Power or Active Power or Real Power).
It is the power that actually powers the equipment and performs useful
work.
KVAR is Reactive Power.
It is the power that magnetic equipment (transformer, motor and relay) needs to produce the magnetizing flux.
KVA is Apparent Power.
It is the vectorial summation of KVAR and KW.
Power factor is an important measurement in electrical AC systems because
  • an overall power factor less than 1 indicates that the electricity supplier need to provide more generating capacity than actually required.
  • the current waveform distortion that contributes to reduced power factor is caused by voltage waveform distortion and overheating in the neutral cables due to yhe generation of harmonics in  three-phase systems.
Reactive power (KVAR) required by inductive loads increases the amount of apparent power (KVA) in our distribution system . This increase in reactive and apparent power results in a larger angle (measured between KW and KVA). We know that, as angle  increases, cosine of that angle (or power factor) decreases.



 So, inductive loads (with large KVAR) result in low power factor.
 
Effect Of Loads:

  • With a purely resistive load current and voltage changes polarity in step and the power factor will be 1. Electrical energy flows in a single direction across the network in each cycle.
  • Inductive loads - transformers, motors and wound coils - consumes reactive power with current waveform lagging the voltage.
  • Capacitive loads - capacitor banks or buried cables - generates reactive power with current phase leading the voltage.
Inductive and capacitive loads stores energy in magnetic or electric fields in the devices during parts of the AC cycles. The energy is returned back to the power source during the rest of the cycles.

DISADVANTAGE OF  LOW PF.:

Increased Power Supply:

We know that inductive loads, which require reactive power, caused our low power factor. This increase in required reactive power (KVAR) causes an increase in required apparent power (KVA), which is what the power plants are supplying. So, low power factor causes the power plants to have to increase its generation and transmission capacity in order to handle this extra demand. By lowering our power factor,we use less KVAR. This results in less KW, which increases savings of power generation.


Other harmful effects are:

*      Increases heating losses in the transformers and distribution equipments.

*      Reduce plant life.

*      Unstabilise voltage levels.

*      Increase  power losses.

*      Decrease energy efficiency.