1. Power Factor Improvement
Of An Induction Motor
Harshit agarwal 22
Under guidance of: Atul kumar sahu 16
Mr. Mohamed Samir Ashish kumar singh 14
Ashish pani vimal 15

2. Introduction Of Induction Motor
•Singly Excited A.C machine.
•Its stator winding is directly connected to A.C source. Where
as its rotor winding receives its energy by Induction
(Transformer Action).
• No load Current in Induction Motor varies from 30 to 50 % of
full load current.
•In Induction motor magnetizing current (lagging nearly 90
degree behind the applied voltage) forms a considerable
portion of No load current that’s why Induction motor have low
power factor at no load.
•The effect of low value of a No load Power Factor is to
decrease the Full Load Operating Power Factor of Induction
motor.

3. Introduction Of Power Factor
• Working /Active Power: Normally measured in kilowatts
(kW). It does the "work" for the system--providing the
motion, torque, heat, or whatever else is required.
• Reactive Power: Normally measured in kilovolt-
amperes-reactive (kVAR), doesn't do useful "work." It
simply sustains the electromagnetic field.
• Apparent Power: Normally measured in kilovolt-
amperes (kVA). Working Power and Reactive Power
together make up apparent power.

4. To understand power factor, visualize a horse pulling a railroad car
down a railroad track. Because the railroad ties are uneven, the
horse must pull the car from the side of the track. The horse is
pulling the railroad car at an angle to the direction of the car’s
travel. The power required to move the car down the track is the
working (real) power. The effort of the horse is the total
(apparent) power. Because of the angle of the horse’s pull, not all
of the horse’s effort is used to move the car down the track. The
car will not move sideways; therefore, the sideways pull of the
horse is wasted effort or nonworking (reactive) power.

5. Power Factor Fundamental
Power Factor : A measure of efficiency. The ratio of Active
Power (output) to Total Power (input)
Power Factor =
Active (Real) Power
Active Power (kW)
Total Power
Reactive
Power
= kW
Total Power (kVA)
(KVAR) kVA
= Cosine (θ)
= DISPLACEMENT POWER FACTOR
A power factor reading close to 1.0 means that electrical power
is being utilized effectively, while a low power factor indicates
poor utilization of electrical power.

6. Why do we care about Power Factor?
• Low power factor results in:
– Poor electrical efficiency!
– Higher utility bills **
– Lower system capacity
– On the Supply Side, Generation Capacity & Line Losses
• Good Power Factor results in:
 Environmental benefit. Reduction of power consumption due to improved
energy efficiency. Reduced power consumption means less greenhouse gas
emissions and fossil fuel depletion by power stations.
 Reduction of electricity bills.
 Reduction of I2R losses in transformers and distribution equipment
 Reduction of voltage drop in long cables.
 Extended equipment life – Reduced electrical burden on cables and
electrical components.
• Power Factor Correction Capacitors (PFCC) provide an
economical means for improving Energy utilization

7. Why do we install Capacitors?
Before After  In this example, demand
was reduced to 8250 kVA
from 10000 kVA.
 1750KVA Transformer
Capacity Release.
 The power factor was
improved from 80% to 97%

8. Power factor correction Of induction motor
•Power factor correction is the term given to a technology that has
been used since the turn of the 20th century to restore the power
factor to as close to unity as is economically viable.
•This is normally achieved by the addition of capacitors to the
electrical network which compensate for the reactive power
demand of the inductive load and thus reduce the burden on the
supply. There should be no effect on the operation of the
equipment.
•To reduce losses in the distribution system, and to reduce the
electricity bill, power factor correction, usually in the form of
capacitors, is added to neutralize as much of the magnetizing
current as possible.
•Capacitors contained in most power factor correction equipment
draw current that leads the voltage, thus producing a leading
power factor

9. MOTOR LOAD CHARACTERISTICS

10. No-load test
1. The motor is allowed to spin freely
2. The only load on the motor is the friction and windage
losses, so all Pconv is consumed by mechanical losses
3. The slip is very small
Poc = Voc * Ioc * Cos(@oc)
Roc = Voc / Ioc Cos(@oc)
Xm = Voc / Ioc Sin(@oc)

11. Blocked-rotor test
In this test, the rotor is locked or blocked so that it cannot move, a
voltage is applied to the motor, and the resulting voltage, current
and power are measured.
Rsc = Psc / (Isc * Isc)
Zsc = Vsc / Isc
Xsc = Under root( sqr(Zsc) – sqr(Rsc))

12. Installation Of Static Capacitor
•This method involves the connection of static capacitor across
stator terminals Of Induction motor.
•In smaller size motors Controlling the Power factor by static
capacitor is a Simplest & most economical method.

13. Phasor Diagram
•The stator current is I1 & motor operating PF
is Cos(@1).
•When Capacitor are connected across stator
terminals, The current Ic through the
capacitors lead the voltage V1 by 90 degree.
•The Phasor sum of I1 & Ic is I1’ drawn by
supply.
•The PF of the combination is improved from
Cos(@1) to Cos (@1’) and stator current
decreases from I1 to I1’.

14. Pertaining to IM PF control By Static
Capacitor
•The stator current locus to the IM is shifted to the left, this shift
being equal to the length of the current phasor Ic.
•This means that the centre of current locus shift from C to C’.
Such that the length CC’ = Ic.
•By the fig. it is clear that if full load PF is near to unity the PF at
No load & Half load are leading.

15. Self Excitation Of IM
•Self-excitation occurs when the capacitive reactive current from
the capacitor is greater than the magnetizing current of the
induction motor. When this occurs, excessive voltages can result
on the terminals of the motor. This excessive voltage can cause
insulation degradation and ultimately result in motor insulation
failure.
Simplified Circuit Diagram for
Motor Controller and Power
Factor Correction Capacitors
(Diagram Shown For Motor
Controller in Open Position)

16. •The rotating magnetic field can be thought of as stored energy.
•When the motor is switched off, the stored energy still present in
the air-gap of the motor begins to collapse and produce a current
in the rotor winding.
•This rotor current induces a voltage on the stator winding and
terminals of the motor which are disconnected (the motor
becomes a generator).
•Because the motor has just been disconnected, it is still spinning
due to its rotating inertial speed which will decrease in time.
•The decaying speed produces a subsequent voltage (and current
flow through the capacitor) at a decaying frequency (starting at a
value near 60 hertz).
•When the frequency of the motor terminal voltage equals the
resonant frequency of the motor and capacitor reactance
combination, high voltage may be produced. This high voltage can
lead to insulation failure on the motor.

17. •To create self-excitation, the capacitive reactance of the capacitor
must be less than that of the motor reactance (this occurs when to
large of a capacitor is chosen).
•If the capacitive reactance is greater than the motor magnetizing
reactance (this occurs for a properly sized capacitor), the resonant
frequency is greater than the motor speed (greater than 60 hertz).
Under this condition, when the motor is disconnected, the
frequency of the decaying terminal voltage will never correspond
with the resonant frequency of the motor and capacitor reactance
combination. Therefore, a high voltage condition will not occur.

18. •The figure shows a plot of the
capacitor and motor magnetizing
voltage verses current waveforms.
•The motor magnetizing curve is
sloped over, which is a
characteristic of iron.
•The capacitor characteristic is a
straight line.
•The curve labeled "A" is sized properly because its capacitive
current is less than that of the magnetizing current at nominal
voltage.
•The curve labeled "B" is sized improperly because its capacitive
current is greater than the magnetizing current at 1 per-unit
voltage.
•When disconnected, the "B" curve in figure 3 shows a valid
operating point at 140% voltage.
•This voltage may occur as the motor slows in speed and passes
through its resonant frequency.

19. The following techniques be used when applying capacitors or
harmonic filers directly on the terminals of an induction motor.
•Request a recommended kvar rating from the motor
manufacturer.
•Size the capacitor at 80% of the no-load current rating
(magnetizing current) of the motor. In no case should the rating be
greater than 90%.
•Utilize recommended capacitor sizing tables induction motors.
•Measure the no-load motor current and size the capacitor at 80%
of the no-load current rating of the motor.

20. Practical Aspects
•Small Induction motor have low Pf than large motor at Low load.
•Small induction motor also have low PF at Full load.
•Our objective Of project is to improve the Power factor Of small
Induction motor at Low as well as Full Load.

21. Procedure & Feasibility Of Project
•Perform No Load test & Blocked Rotor test to find out Internal
impedance of the Motor.
•Determining The power factor & Efficiency of the Motor.
•Making calculations For the size of Capacitor Bank should be
install to Improve the Power factor.
•Determining The New improved Power Factor & Efficiency.
•Compare the New Power Factor With Previous Power Factor.
•Calculation for the Net saving In operating cost Of the Motor.
By the best of our research and Knowledge this
project is feasible & worth while to perform.