WELCOME POWER FACTOR CORRECTION
Rajat Kumar Barik
1. Power factor is the percentage of electricity that is being used to do useful work
2. Power factor =Active power/Apparent power
3. Apparent power has two component:
(a) Active power
o ACTIVE POWER: Active power does all the work.
o UNIT : kw
o P= v I cos
o REACTIVE POWER: I t is the pseudo power(false) power which flows from source to load during +ve half and load to source during â€œve half cycle.
o UNIT : Kvar
o Q= v I sin
DISADVANTAGE OF LOW POWER FACTOR
(A)Larger kva rating of equipment
Kva = kw / cos
If cos will decrease then kva rating will increase
So we have to make equipment larger which is expensive
B)GREATER CONDUCTOR SIZE:
P =V I COS
=> I= (P/ VCOS)
If powerfactor will decrease then current will increase.
So for conducting heavy current we have to
install large size Conductor.
© Copper loss
At low power factor the current drawn by the system will increase. Due to increase in current the copper loss will increase .
(d) Poor voltage regulation
The large current in low power factor causes a high voltage drop and the voltage at the receiving side is low.
In order to keep the constant voltage at the receiving side we have to install extra equipment (voltage regulators) is required.
EQUIPMENT CREATING POOR POWER FACTOR
o LIGHTING INCANDESCENT LAMPS.FLUORESCENT LAMP.
o MERCURY VAPOUR LAMPS.
o DISTRIBUTION TRANSFORMER.
o INDUCTION MOTOR.
o SYNCHRONOUS MOTORS
o INDUSTRIAL HEATING
BENEFITS OF POWER FACTOR CORRECTION
Reduce utility power bills :
(a) For consumer
: A consumer has to pay electricity charges for his maximum demand in Kva plus the unit consumed. If the consumer improves the power factor then there is a reduction in Kva requirement. So there will be a annual saving.
(b)For generating station
: Generating station is as much concerned with power factor improvement as the consumer . The generators in a power station are rated in Kva but the output will depend on Kw.
Increase system capacity
Improve operating characteristics (Gain voltage)
Improve system operating characteristics (Reduce line losses)
Types of power factor correction
Power factor correction can be made in three ways
(1) Capacitor bank
The power factor can be improved by connecting capacitors in parallel with the equipment operating at lagging power factor .
The capacitor (generally known as static capacitor ) draws a leading current and partly naturalized the lagging reactive component of load current. This raises the power factor of the load.
DIRECTION of current before compensation
Direction of current after using capacitor bank
(2) Synchronous condenser
o A synchronous motor takes a leading current when over excited and therefore behaves as capacitor .
o An over excited synchronous motor running on no load is known as synchronous condenser. When such machine is connected in parallel with the supply , it takes a leading current which partly naturalizes the lagging reactive component of the load. Thus power factor can be improved.
(3) Phase advancers:
Phase advancer are used to improve the power factor of induction motors .The low power factor of an induction motor is due to the fact that its stator winding draws exciting current which lags
behind the supply by an angle of 90 degree.
If the exciting ampere turn can provided from some other a.c source then stator winding will be relived of exciting current and the power factor can be improved.
Lastly after the completion of my seminars , I conclude that improvement of power factor is necessary in both consumer end and supplier point of view . In some industries penalty is charged due to low power factor. In some industries where power consumed by the load is low , high ratings of equipment s are required.
SVC technology and synchronous generator are used for the improvement of power factor.