4. POWER FACTOR IS A MEASURE OF THE ELECTRICAL
SYSTEMS EFFICIENCY THE TOTAL ELECTRICAL POWER
(KILO VOLT AMPERES OR KVA) USED IN AN ELECTRICAL
SYSTEM BY AN INDUSTRIAL .
Need for Power Factor :
5. Need for Power Factor :
AC POWER FLOW HAS TWO COMPONENTS:
REAL POWER OR ACTIVE POWER (P) EXPRESSED IN WATTS (W)
REACTIVE POWER (Q), USUALLY EXPRESSED IN REACTIVE VOLT-AMPERES (VAR)
THESE ARE COMBINED TO THE COMPLEX POWER (S) EXPRESSED VOLT-AMPERES (VA). THE
MAGNITUDE OF THE COMPLEX POWER IS THE APPARENT POWER (|S|), ALSO EXPRESSED IN VOLT-
AMPERES (VA).
THE POWER FACTOR IS DEFINED AS THE RATIO OF REAL POWER TO APPARENT POWER. AS POWER IS
TRANSFERRED ALONG A TRANSMISSION LINE
6. Need for Power Factor :
IF Θ IS THE PHASE ANGLE BETWEEN THE CURRENT AND VOLTAGE, THEN THE POWER FACTOR IS
EQUAL TO THE COSINE OF THE ANGLE,
7. Cause of power Factor
THE MAIN CAUSE OF LOW POWER FACTOR IS INDUCTIVE
LOAD. AS IN PURE INDUCTIVE CIRCUIT, CURRENT LAGS 90°
FROM VOLTAGE, THIS LARGE DIFFERENCE OF PHASE ANGLE
BETWEEN CURRENT AND VOLTAGE CAUSES ZERO POWER
FACTOR. BASICALLY, ALL THOSE CIRCUIT HAVING
CAPACITANCE AND INDUCTANCE (EXCEPT RESONANCE
CIRCUIT (OR TUNE CIRCUIT) WHERE INDUCTIVE REACTANCE
= CAPACITIVE REACTANCE (XL = XC), SO THE CIRCUIT
BECOMES A RESISTIVE CIRCUIT), POWER FACTOR WOULD BE
EXIST OVER THERE BECAUSE CAPACITANCE AND
INDUCTANCE CAUSES IN DIFFERENCE OF PHASE ANGLE (Θ)
BETWEEN CURRENT AND VOLTAGE.
8. Need for Improvement PF
POWER FACTORS BELOW 1.0 REQUIRE A UTILITY TO GENERATE MORE THAN THE MINIMUM
VOLT-AMPERES NECESSARY TO SUPPLY THE REAL POWER (WATTS). THIS INCREASES
GENERATION AND TRANSMISSION COSTS. FOR EXAMPLE, IF THE LOAD POWER FACTOR WERE
AS LOW AS 0.7, THE APPARENT POWER WOULD BE 1.4 TIMES THE REAL POWER USED BY THE
LOAD. LINE CURRENT IN THE CIRCUIT WOULD ALSO BE 1.4 TIMES THE CURRENT REQUIRED AT
1.0 POWER FACTOR, SO THE LOSSES IN THE CIRCUIT WOULD BE DOUBLED
WITH THE RISING COST OF ENERGY AND CONCERNS OVER THE EFFICIENT DELIVERY OF POWER,
ACTIVE PFC HAS BECOME MORE COMMON IN CONSUMER ELECTRONICS.[28] CURRENT ENERGY STAR
GUIDELINES FOR COMPUTERS[29] CALL FOR A POWER FACTOR OF ≥ 0.9 AT 100% OF RATED OUTPUT IN
THE PC'S POWER SUPPLY.
9. 1.) LARGE LINE LOSSES (COPPER LOSSES):
WE KNOW THAT LINE LOSSES IS DIRECTLY PROPORTIONAL
TO THE SQUIRE OF CURRENT “I2”
POWER LOSS = I2XR I.E., THE LARGER THE CURRENT, THE
GREATER THE LINE LOSSES I.E. I>>LINE LOSSES
IN OTHER WORDS,
POWER LOSS = I2XR = 1/COSФ2 ….. REFER TO EQUATION
“I ∝ 1/COSФ”….… (1)
THUS, IF POWER FACTOR = 0.8, THEN LOSSES ON THIS
POWER FACTOR =1/COSФ2 = 1/ 0.82 = 1.56 TIMES WILL BE
GREATER THAN LOSSES ON UNITY POWER FACTOR.
Disadvantage of low power Factor
10. Methods for improving P
P.E‡
.
The following devices and equipment are used
for Power Factor Improvement.
1.Static Capacitor
2.Synchronous Condenser
3.Phase Advancer
