This document discusses power factor and methods for improving it. It defines power factor as the ratio of active power to apparent power. Low power factor is caused by inductive devices and indicates inefficient electricity use. Correcting power factor through capacitors can provide benefits like increased plant capacity and reduced utility charges. Capacitors work by opposing inductive lagging current. They can be installed at individual equipment, equipment groups, or at the main service, with various tradeoffs to consider. Harmonic distortion from devices like variable speed drives can also impact power quality if not properly addressed.

1. Institute Of Textile And Fashion
Technology/EiTEX/
Bahir Dar University
Prep. By:- Beyene Dumecha
May, 2008 E.C
Advisor:-
Dr.Solomon T.
MSc in Textile Chemistry
Seminar presentation on power factor

2. Introduction
• Power Factor gives a reading of overall electricity use
efficiency.
• High power factor indicates that the amount of power
doing real work is operating at a high level of efficiency.
• Conversely, low power factor means poor electricity
efficiency which is always costly.
• Improving power factor can reduce billed peak demand
and enhance equipment reliability.

3. POWER FACTOR
• It is the mathematical ratio of ACTIVE POWER () to
APPARENT POWER (VA).
pf angle in degrees = cos–1 θ

4. • ACTIVE POWER = W = “real power” = supplied by
the power system to actually turn the motor.
• REACTIVE POWER = VAR = (W)tan θ = is used
strictly to develop a magnetic field within the motor.
• NOTE: Power factor may be “leading” or “lagging”
depending on the direction of VAR flow.

5. WHY RAISE POWER FACTOR (pf)?
• Low (or “unsatisfactory”) power factor is caused by the
use of inductive (magnetic) devices and can indicate
possible low system electrical operating efficiency.
 These devices are:
• non-power factor corrected fluorescent and high intensity
discharge lighting fixture ballasts (40%-80% pf).
• arc welders (50%-70% pf)

6. • solenoids (20%-50% pf)
• induction heating equipment (60%-90% pf)
• lifting magnets (20%-50% pf)
• small “dry-pack” transformers (30%-95% pf) and
• most significantly, induction motors (55%-90% pf)

7. • Induction motors are generally the principal cause of
low power factor because there are so many in use,
and they are usually not fully loaded.
• The correction of the condition of LOW power factor is
a problem of vital economic importance in the
generation, distribution and utilization of A-C power.

8. • MAJOR BENEFITS OF POWER FACTOR IMPROVEMENT
ARE:
– increased plant capacity,
– reduced power factor “penalty” charges for the electric
utility,
– improvement of voltage supply,
– less power losses in feeders, transformers and
distribution equipment.

9. WHERE TO CORRECT POWER FACTOR?
• Capacitor correction is relatively inexpensive both in material
and installation costs.
• Capacitors can be installed at any point in the electrical system,
and will improve the power factor between the point of
application and the power source.
• However, the power factor between the utilization equipment
and the capacitor will remain unchanged.
• Capacitors are usually added at each piece of offending
equipment, ahead of groups of small motors (ahead of motor

10. CAPACITORS
• CAPACITORS can be used to improve the power factor
of a circuit with a large inductive load.
• Current through capacitor LEADS the applied voltage by
90 electrical degrees (VAC), and has the effect of
“opposing” the inductive “LAGGING” current on a
“one-for-one” (VAR) basis.

11. CAPACITORS

12. Advantages and Disadvantages of
Capacitor

13.  Capacitor on each piece of equipment (1,2)
ADVANTAGES
• increases load capabilities of distribution system.
• can be switched with equipment; no additional switching is
required.
• better voltage regulation because capacitor use follows load.
• capacitor sizing is simplified
• capacitors are coupled with equipment and move with equipment if
rearrangements are instituted.
small capacitors cost more per KVAC than larger.
DISADVANTAGES

14.  Capacitor with equipment group (3)
ADVANTAGES
• increased load capabilities of the service,
• reduced material costs relative to individual correction
• reduced installation costs relative to individual correction
DISADVANTAGES
• switching means may be required to control amount of capacitance
used.

15.  Capacitor at main service (4,5, & 6)
ADVANTAGES
• low material installation costs.
DISADVANTAGES
• switching will usually be required to control the amount
of capacitance used.
• does not improve the load capabilities of the distribution
system.

16. OTHER CONSIDERATIONS
• Where the loads contributing to power factor are relatively constant, and
system load capabilities are not a factor, correcting at the main service
could provide a cost advantage.
• When the low power factor is derived from a few selected pieces of
equipment, individual equipment correction would be cost effective.
• Most capacitors used for power factor correction have built-in fusing; if
not, fusing must be provided.
• The application of pf correction capacitors without a thorough analysis of
the system can aggravate rather than correct the problem, particularly if
the fifth and seventh harmonics are present.

17. • The electronic circuits used in ASDs may be susceptible
to power quality related problems if care is not taken
during application, specification and installation.
• The most common problems include transient over
voltages, voltage sag and harmonic distortion.
• These power quality problems are usually manifested in
the form of nuisance/trouble/ tripping.
POWER QUALITY REQUIREMENTS

18. • TRANSIENT OVERVOLTAGES—Capacitors are devices
used in the utility power system to provide power factor
correction and voltage stability during periods of heavy
loading.
• Customers may also use capacitors for power factor
correction within their facility.
• When capacitors are energized, a large transient
overvoltage may develop causing the ASD to trip.

19. • VOLTAGE SAGS—ASDs are very sensitive to temporary reductions in
nominal voltage.
• Typically, voltage sags are caused by faults on either the customer’s or
the utility's electrical system.
• HARMONIC DISTORTION—ASDs introduce harmonics into the power
system due to nonlinear characteristics of power electronics operation.
• Harmonics are components of current and voltage that are multiples of
the normal 60Hz ac sine wave.
• ASDs produce harmonics which, if severe, can cause motor, transformer
and conductor overheating, capacitor failures mis-operation of relays
and controls and reduce system efficiencies.

20. THANK YOU!!