Answer / amit upadhyay dscl

because
cos$ = R/Z ........... ($=phai),
where R=resistance & Z=impedance
total impedance without capacitor,
Z=root square of(R square + XL square)
total impedance with capacitor,
Z=root square of{R square + (XL-XC) square}
due to decrease of (XL-XC) total impedance with capacitor
decreases, and due to this, power factor increases. because
from equation first,
cos$ perportional to 1/Z

Answer / bala

current leads the voltage by 90 degree by adding the
capacitor bank. this helping to increase the power factor.

Answer / amirtha

in capacior we having leading power factor.so it is used to
improve power factor.

Answer / mohan

An electrical load can be inductive or resistive(filament
bulb).
for an inductive load the energization power is required ,
isnce this is called reactive power(imaginary magantising
power) , which is non productive.
You can draw paralles to your Savings Bank account - where
you need to maintain certain amount as minimum balance,
which you can not withdraw.

again this "magnatising current" is load dependant and will
varry according to the load. for example if you are riding
a bicycle , the minimum force needed to be given for moving
the cycle must be higher than than Weights(your+Cycle)
*gravitation force.
The base value weight* gravitational force can be imagined
as reactive power and, when you ride the cycle in elevated
path u put extra energy and on a slope u need less energy.
Capacitor is a supplier of reactive energy and if you use
capacitor to compliment the reactive power then you will
have reduced kva withdrawal from grid.
KVA = SQRT[kw*kw)+(kvar*kvar)]
PF = kw/kva. in other words PF is the efficincy of yor
power conversion. since it is the ratio of output(KW you
consume ) to the input(the withdrawal from grid)

Answer / viswanathan

we are using induction motors for industrial and domestic
purpose.inductions motors working with reactive power.it
leads to lagging power factor.so we put the capacitor
(active power)for compensat the reactive power.

Answer / p.muralikrishna

My dear friend,
I think you are aware of mechanical fly wheel. This sores
energy when there is excess of supply and supplies the
stored energy when there is short to the extent of its
storing capacity. Also as the capacitor draws a leading
current in contrast to generally lagging current by
inductive load. Thus capacitor tries to bring the load
current nearer to resistive.

Answer / ashish patel

My dear friend,

I m describing the answer very simply. If the load is
inductive load i.e. 100 Amp motor load. Then some current
i.e. 75% (75 A) will be drawn by Electricity line & balance
25% (25 A) will be drawn by Capacitors if they are connected
before load. so Electricity billing reduced only for 75 Amp
instead of 100 Amp.

I m using same system for transformer testing. So
technically we can say that we improve PF by using
capacitors, so that we get benifit in Electricity Billing.
If you want further clarification, plz write me on
ashish_patel111@yahoo.com

Any one can explain if there is any harm from humming noise heard from air circuit breaker : we have 415 switch board having two incomers from transformers 3.3KV/415V , when bus coupler closed, and open one ACB incomer to work in one of the transformers, the current started hunting around 50 Amps, and heard humming noise from the air circuit breaker, although the load current was only 1200 amps while the ACB capacity is 2500 Amps, and the transformer 1600 KVA. The same didn't happen when taken the other transformer offline. Why this humming noise and current fluctuation? is there any implication or danger, bearing in mind that we just returned everything back to normal and stopped the maintenance of the transformer. Shall we go ahead and ignore this noise?

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