Sunday 24 September 2017

Important of Power factor(pf) in AC system.

A number of power quality issues including electrical harmonics, poor power factor, voltage instability and imbalance, impact on the efficiency of electrical equipment's.

1)What is power factor ?

In Alternative current (AC) system have two quantity namely voltage and current, the power factor has cosine angle between the voltage and current.
Pf will be lagging & leading depends upon load connected.
if inductive load such as motor pf of the circuit lagging,where capacitive load such as capacitor
have leading pf.

2)Lossless because low power factor(pf) ?

~High energy uses and costs.
~ Failure of motors.
~Failure of electrical and  electronics equipment.
~Malfunction of Fuses & Circuit Breakers.
~Unstable equipment operations.
~Overheating of transformers and switch-gears.

3)How does Power Factor Correction work?

#see_video_how power factor improved

Power Factor is the ratio of Active Power(KW) to the Apparent Power(KVA) drawn by any load. 

Low power factor leads to increased transmission and distribution losses leads to increased electricity bills without increase in productivity, heating & hunting of DG with increased fuel consumption.

Pf =kw/KVA
True power/apparent power.
Generally power factor in varies between 0 to 1.
it is best practice to maintain power factor unity(1).

 PFC systems increase the efficiency of power supply, delivering immediate cost savings on electricity.

    Real Power is the power that actually powers the equipment and performs useful, Productive work.

    Reactive Power is required by some equipment (e.g. transformers, motors and relays) to produce a magnetic field for operation; however it does not perform any real work.

    Apparent Power is the vector sum of Real and Reactive Power and corresponds to the total power required to produce the equivalent amount of real power for the load.

A capacitor generate leading power factor for compensation of inductive power factor,
In term of KVAR.
Where KVAR known reactive power,equal to

Voltage x current x sin Phi.

4) how to calculate pf.?

Q-1) a 10 KW induction motor operate in 220 volt 50 hz power supply, if motor 50 ampere current ,then calculate power factor of motor.
Q-2) if require maintain power factor 0.98,calculate VAR value of capacitor.

Given in Q-1
Active power(KW)=10
apparent power =V x I x cosine

Cosine = KW/VI

if require 0.98 pf.
KVAR =V x I x sin phi
           = V x I x √[ 1-pf x pf]

              11 x √[1-0.98 x0.98]
            =11 x 0.4
             =0.440 KVAR

Hence 440 VAR capacitor bank require to maintain 0.98 pf of induction motor, to efficient operation and save electricity bill.

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