22-05-2012, 02:50 PM
Power Factor and APFC
Origin of Low Power Factor
Electrical Equipment need Reactive Power
Inductive loads draw Reactive Power
Phase difference between current & Voltage reduces “Displacement PF”.
Reactive Power to maintain magnetic fields in Motors.
Non-Linear loads reduces “Distortion PF”.
True PF, being product of displacement and distortion PF is lower than both.
Disadvantages of low power factor
Inefficient use of Electrical Energy:
Overloading of Transformer/Generator;
Overloading of Cable, Switchgear, Busbar …
Higher temperature due to increased losses
Imposes larger kVA demand
Limits No. of loads that can be connected
Reduced revenue to Electrical Utilities
Poor Voltage regulation
Disadvantages of fixed capacitor
Manual operation(on/off)
Not meet the require kvar under varying loads.
Can result leading power factor
Cause over voltage
Mal-operation of relays, diesel generators
Saturation of transformer
Penalty by electricity authority
NEED FOR AUTOMATIC POWER FACTOR CORRECTION
varying power demand on the supply system.
power factor also varies as a function of the load requirements.
difficult to maintain a consistent power factor by use of Fixed Compensation i.e. fixed capacitors.
leading power factor under light load conditions(fixed compensation)
This result in over voltages, saturation of transformers, mal-operation of diesel generating sets, penalties by electric supply authorities.