1. Power Factor basics
By: Jafar Khan

2. Content
 What is power factor
 What causes low power factor
 Why should I improve my power factor
 How should I correct (Improve) my power factor

3. What is Power Factor?
Power factor is the measure of how effectively your electrical
equipment converts electric power (supplied by your power utility)
into useful power output.
In technical terms, it is the ratio of Active Power (kW)) to the
Apparent Power (kVA) of an electrical installation.

4. • 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.

5. Simple analogy in order to better understand these terms….
P.F. = KW
KVA
P.F. =
KW
KW+KVAR
P.F. =
Beer
Beer+Foam
 The more foam you have (the higher the percentage of KVAR), the lower your
ratio of KW (beer) to KVA (beer plus foam). Thus, the lower your power factor.
 The less foam you have (the lower the percentage of KVAR), the higher your ratio
of KW (beer) to KVA (beer plus foam). In fact, as your foam (or KVAR) approaches
zero, your power factor approaches 1.0.

6. Let’s look at another analogy ……
Mac here is dragging a heavy load. Mac’s Working Power (or
Actual Power) in the forward direction, where he most wants his load to
travel, is KW.
Unfortunately, Mac can’t drag his load on a perfect horizontal (he would
get a tremendous backache), so his shoulder height adds a little Reactive
Power, or KVAR.
The Apparent Power Mac is dragging, KVA, is this “vectorial summation”
of KVAR and KW.

7. KVAR (Reactive Power)
Power Traingle ……
Power Traingle…
KV
A
(Ap
par
e
nt
P
ow
er)
Ø
KW (Real Power)
= COS Ø
Power Factor (COS Ø) should be close to unity

8. What causes Low Power Factor?
Low power factor results when KW is small in relation to KVA.
Remembering our beer mug analogy, this would occur when KVAR (foam, or Mac’s
shoulder height) is large.
What causes a large KVAR in a system? The answer is…inductive loads.
􀂉 Transformers
􀂉 Induction motors
􀂉 Induction generators (wind mill generators)
􀂉 High intensity discharge (HID) lighting

9. KVAR
KVAR
KVAR
 Reactive power (KVAR) required by inductive loads increases the amount of
apparent power (KVA) in distribution system.
 This increase in reactive and apparent power results in a larger angle
measured between KW and KVA.
 As θ increases, cosine θ (or power factor) decreases.
KV
A
KV
A
KV
A
Ø
Ø
KW
KW

10. Why should I Improve my Power Factor?
• Lower the Utility bill
inductive loads require reactive power, caused your low power factor. This
increase in required reactive power (KVAR) causes an increase in required
apparent power (KVA), which is what the utility is supplying.
So, a facility’s low power factor causes the utility to have to increase its
generation and transmission capacity in order to handle this extra demand.
By raising your power factor, you use less KVAR. This results in less KW,
which equates to savings from the utility.
• Increased system capacity and reduced system losses
By adding capacitors (KVAR generators) to the system, the power factor is
improved and the KW capacity of the system is increased.
Reduces I2R losses in conductors

11. • Increased voltage level and cooler, more efficient motors
As uncorrected power factor causes power losses in distribution system. As
power losses increase, you may experience voltage drops. Excessive voltage
drops can cause overheating and premature failure of motors and other
inductive equipment.
So, by raising power factor, minimizes these voltage drops along feeder cables
and avoid related problems. Your motors will run cooler and be more efficient,
with a slight increase in capacity and starting torque.
A 10% drop in terminal voltage from the rated,
 Will reduce the Induction motor torque by approx 19%,
 Increase full load current by approx 11%,
 Reduce overload capacity
 Increase temperature rise by approx 6-7 degrees.

12. Five lightson
Fourlight on
Three lights
Twolightson on
Onelights on
Six lights on
No
25
24
23 Watts total
20Watts total
14
0
(room gets brighter)
(some light darker)
(room is dark)room)
in
Voltage drops more
Voltage is normal
some

13. 12/11/97
13

14. • Reduces loading on transformers
For example, a 1,000 KVA transformer with an 80% power factor provides 800
KW (600 KVAR) of power to the main bus.
1000 KVA =
(800 KW)2 + ( ? KVAR)2
KVAR = 600
By increasing the power factor to 90%, more KW can be supplied for the same
amount of KVA.
1000 KVA =
(900 KW)2 + ( ? KVAR)2
KVAR = 436
The KW capacity of the system increases to 900 KW and the utility supplies only
436 KVAR.

15. How do I correct my Power Factor?
We have seen that consumers of Reactive power (Inductive loads) decrease
power factor
Similarly, Sources of Reactive Power increase power factor:
􀂉 Capacitors
􀂉 Synchronous generators (utility and emergency)
􀂉 Synchronous motors
One way to increase power factor is to add capacitors to the system.

16. • Installing capacitors (KVAR Generators)
Installing capacitors decreases the magnitude of reactive power (KVAR), thus
increasing your power factor.
Reactive power (KVARS), caused by inductive loads, always acts at a 90-degree
angle to working power (KW).
Capacitance (KVAR)
Working power (KW)
Reactance (KVAR)
Capacitors store KVARS and release energy opposing
the reactive energy caused by the inductor.

18. If the motor is unloaded and is located a short distance from the generator,
the energy from the generator causes magnetic fields to form around the
motor coils.
Reactive power
In both directions between the
generator and the motor
Feeder line
True power
delivered to load
Generator
Output—apparent power
(Combination of true and reactive power)

19. Since the coils of the motor are reactive, the current causes a magnetic
field to expand around the coils during one portion of the alternation.
During another portion of the alternation, the magnetic field collapses,
induces a voltage at the coil, and causes current from the motor to flow
back to generator.

20. The current causes a magnetic field to expand around the coils during one
portion of the alternation.
Reactive power from the
generator to the motor
For Ascending
Positive Alternation

21. During another portion of the alternation, the magnetic field collapses,
induces a voltage at the coil, and causes current from the motor to flow
back to generator.
Reactive power from the
motor to the generator
For Descending
Positive Alternation

22. The current causes a magnetic field to expand around the coils during one
portion of the alternation.
Reactive power from the
generator to the motor
For Ascending
Negative Alternation

23. During another portion of the alternation, the magnetic field collapses,
induces a voltage at the coil, and causes current from the motor to flow
back to generator.
Reactive power from the
motor to the generator
For Descending
Negative Alternation

26. Individual Correction

27. Group Correction

28. Capacitor sizing
KVAr required = kW (tan Ø 1 – tan Ø 2)
Where Ø 1 = Cos-1 (PF 1) and
Ø 1 = Cos-1 (PF 2) and
PF1 and PF2 are initial and final
Power factors respectively
Q=
S2 - P2

29. Conclusion
 PF is the ratio of Active Power (kW)) to the Apparent Power
(kVA).
 More the reactive power, less is the power factor
 Power factor can be improved by locally providing required
Reactive power

30. Thank You