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I hv a question regarding power factor improvement just
after transformer. I request you to reply me plzz. thank
you sir.
My friend has a small unit of fabrication. in his factory
the main load is a welding machine, lathe machine, grinding
machine. this load is not continuous type. now our
electricity board has installed 16 KVA, 11000/433 V
transformer for our factory. In the energy meter (trivector
meter) at LV side of transformer, i hv seen power factor
value of 0.15 only when only 3 KW load was flowing. Further
electricity board has suggested to install 4 KVAR capacitor
at LV side after energy meter. Now my question is that if
we permanantly install and switch on 4 KVAR capacitor after
energy meter, during some load on transformer and also
without any load on transformer, wht will be the power
factor shown in energy meter?i dont want to get any penalty
by electricity board, so plz suggest me if i can
permanantly install and switch on the 4 kvar capacitor or
not at LV side of transformer just after energy meter?
Thank you again and awaiting for ur positive reply soon.

Answers were Sorted based on User's Feedback



I hv a question regarding power factor improvement just after transformer. I request you to reply ..

Answer / surya

the 4kvar capacitor improve the pf but you must keep in
mind that installed the capacitor permanentely only at load
time.switched off the capacitor on unload time since i
think at unload time the 4kvar capacitor become a self-load
& increase your electricity bill.

Is This Answer Correct ?    2 Yes 0 No

I hv a question regarding power factor improvement just after transformer. I request you to reply ..

Answer / hareesh

The purpose of capcitor is to improve pf according to
load.the worst pf at no load.at no load capacitor draws
more current than full load and improve pf.power consuming
by the capacitor is reactive power which will not count by
EM.

required capa.(kvar)=p*(tan(inv cos(pf1))- tan(inv cos(pf2))

p= total power in kw
pf1=actual pf
pf2=required pf

Is This Answer Correct ?    2 Yes 0 No

I hv a question regarding power factor improvement just after transformer. I request you to reply ..

Answer / raj

You have to calculate and put partially some capacitor
permanentely ON which will neutralized or improve the PF
when Transformer charged with NO load condition and other
capacitor should be connect through contactor so that as
welding machine will on capacitor will on ( interlocking
between both ).If PF increase or reached to Leading side
means it will work as a load and you have to pay extra
amount in your bill.
PF Calculation Formula

required capa.(kvar)=p*(tan(inv cos(pf1))- tan(inv cos(pf2))

p= total power in kw
pf1=actual pf
pf2=required pf

Is This Answer Correct ?    2 Yes 0 No

I hv a question regarding power factor improvement just after transformer. I request you to reply ..

Answer / ranadev datta

The transformer at no load has a pf depending on relative
values of its no-load kW loss and the apparent no-load kVA.
A capacitor permanently connected to the LV side should be
of a kVAR value to just correct the inductive kVAR at no-
load and no more.

Separate sets of capacitors should be judiciously applied
to correct the pf on load. The best thing to do is to
switch the pf-improvement capacitors on and off along with
the switching of the individual offending loads (e.g., by
connecting the capacitors of appropriate ratings to the
motor terminals) thereby bringing about
inherently 'automatic' control of capacitor switching.

Is This Answer Correct ?    1 Yes 0 No

I hv a question regarding power factor improvement just after transformer. I request you to reply ..

Answer / rameez ajmeri

when the capacitor is switched on at load it will improve
the power factor, but you have to take care that the
capacitor is switched on when there is no load on the
transformer...we have to take care about that...

Is This Answer Correct ?    2 Yes 2 No

I hv a question regarding power factor improvement just after transformer. I request you to reply ..

Answer / arsenal

capacitors connected on the lv side at no load will take
charging current...........as a result it will act as a
self load...........

Is This Answer Correct ?    0 Yes 0 No

I hv a question regarding power factor improvement just after transformer. I request you to reply ..

Answer / k.prakashchandra

Most of the Elec boards consider only the average pf which
is =Kwh/Kvah for the billing month.Fix individual capacitors
on load side or APFC

Is This Answer Correct ?    0 Yes 0 No

I hv a question regarding power factor improvement just after transformer. I request you to reply ..

Answer / m s venkateswara rao

It is not possible to maintain constant power factor at variable load. A little bit expensive but you have to go for procure auto pf panel, installed and connected immediately after EB meter.In APF panel controller you should set the pf range so that at different loads APF panel will automatically will switch on different rating of capacitors to maintain set pf.

Is This Answer Correct ?    0 Yes 0 No

I hv a question regarding power factor improvement just after transformer. I request you to reply ..

Answer / amrinder

how capacitors connected in parallel to each phase i.e
R,Y,B giving a resultant of 4 KVAR become a self load at
noload time of transformer and increase the electricity
bill.......... please explain in detail......waiting

Is This Answer Correct ?    0 Yes 1 No

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