POWER FACTOR :- IT IS THE PHASE ANGLE BETWEEN THE VOLTAGE AND THE CURRENT.
IN A PURELY RESISTIVE CIRCUIT THE VOLTAGE AND CURRENT WAVEFORM ARE IN PHASE WITH ONE ANOTHER AND THEY CHANGE THEIR POLARITY AT SAME INSTANCE, HENCE ALL THE SOURCE ENERGY IS TRANSFERED TO THE AVAILABLE LOAD.
BUT IN A REACTIVE LOAD SUCH AS INDUCTOR OR CAPACITY, SOME ENERGY STORED IN THE LOAD CAUSES A TIME DIFFERENCE BETWEEN THE CURRENT AND VOLTAGE WAVEFORM AND SOME PERCENTAGE OF ENERGY IS RETURNED TO THE SOURCE. SINCE THIS STORED ENERGY IS NOT AVAILABLE TO DO WORK AT THE LOAD, IT IS CALLED APPARENT POWER.
NOW LET US SEE THE ADVANTAGES OF A HIGHER POWER FACTOR:-
- LET US SUPPOSE WE HAVE 2 INDUCTION MOTOR OF KW RATING 100 KW EACH. NOW LET THE POWER FACTOR OF ONE BE 0.6 AND 0.8. THEN ACCORDING TO EQUATION
KW=KVA*POWER FACTOR
= VOLTAGE*CURRENT*POWER FACTOR
NOW IF WE HAVE SAME POWER FACTOR AND VOLTAGE IS USUALLY SAME THEN THE MOTOR WITH LOW POWER FACTOR WILL DRAW MORE CURRENT. THIS WILL LEAD TO MORE LOSSES AS COPPER LOSS DEPENDS ON CURRENT. MORE THE CURRENT DRAWN MORE WILL BE THE LOSSES.
2. LIKEWISE IF A MOTOR IS HAVING LOW POWER FACTOR THEN ITS WINDING HAS TO BE THICKER TO SUSTAIN MORE CURRENT AND HENCE MAKE THE MOTOR HEAVY.
3. LOW POWER FACTOR ALSO INCREASES TRANSMISSION LOSSES.
4. IF POWER FACTOR IS LOW IT CAN DAMAGE THE MACHINES WHICH ARE SENSITIVE TO REDUCED VOLTAGE.