Answer / ashish sharma

if we have a dg set of 500kva its name plate shows
1.732*415*500*.8 is equal to 400kw but if we use pf.9
then 1.732*415*.9*500 is equal to 450kw that is more than
its capacity thats why we can not use capactor bank in dg
set

Answer / kishor kajrolkar

It is possible to switch on high speed microprocessor
based capacitor bank on running d g set.But with A P F C
ie. contactor based can be used with time delay So as it
will result in zero voltage available on terminal of the
capacitor.( during switching of said capacitor bank on
running generator).However one must think of no load
condition of the d g set so as to use sensitive steps for
capacitor in the circuit.It is observed most of the load
in IT sector having non linear loads ,hence result in
impure power as well as low powerfactor leads to additional
loads.Capacitor used to filter harmonic current and change
of the power factor need to classified before application
the bank.

Answer / ravisankar dhayalan

DG set is a power source. Capacitor bank is required for a
load to maintain the power factor i.e. reactive power. The
alternators are designed for 0.8 pf. if the load pf is lower
than this value, it will overload alternator. under such
conditions it is necessary to install a capacitor bank.

Answer / p.j.s.raju

Hi i am P.J.S.Raju
above the answers I read in D.G set .8pf is designed when generator running time we more then of D.G load .There incoming braker will trip ,so capacitor no need in generator. Maintained p.f exitor field through AVR.

Answer / p.j.s.raju

I am p.j.s.raju above the answers I read when generator is running maximum load maintain the 0.8 PF increase the over load of generator incoming brake will be trip, other wise we can add capacitor p.f maintain uniti 1 p.f .but we loss 15 present of generator out put power. So APR maintain power factor automatically then not required capacitor.

Answer / prashant pandey

Total power KVA is the square root of the sum total of the squares of active power (KW) and reactive power (KVAR). Here the active power is VICos$ which is the actual useful power whereas the reactive power is the imaginary power or wastage in lay man's terms. Cos$ is the power factor, which should be ideally equal to 1 for minimum wastage of power and maximum useful power.
In Inductive circuits, Current tends to lag the voltage whereas in capicitive circuits it tends to lead the voltage. In case we have a lot of inductive load on the DG sets, capacitor bank to balance the inductive load so that the PF is as close to 1 as possible will be definitely useful. It has been practilly observed that the total load ampere of the DG reduces resulting in better utilization of DG capacity. In absence of inductive load, capacitor bank will not be required. Capacitor bank is to be used only to the extent of balancing the inductive load, for better utilization of the DG set.

Answer / saeed

The field excitation current requirement for a loaded generator depends very much
on the power factor of the load current and in the usual case of lagging power factor
the field current increases as the power factor reduces. On the other hand, with
leading power factor loads the effect is the opposite and as the power factor reduces,the field current requirement for a given output will go down. If the leading power factor of the load circuit is reduced sufficiently, a condition may be reached in which the field current requirement becomes zero and this is known as self-excitation. At this critical point the AVR sensing the generator output voltage would lose control, and any further reduction of the leading power factor would cause overexcitation and the voltage would rise without any corrective action from the AVR. Such a condition is obviously most undesirable and could cause damage to the connected load.
Because self-excitation depends on armature reaction effects from the stator
winding, modern a.c. generators which have high synchronous reactance will reach
this point of voltage instability at a lower level of reactive load than older type
machines which tended to have lower synchronous reactance values. Circuits which have any risk of self-excitation should be carefully examined before arranging to feed them from a generating set supply and in doubtful cases it may be necessary to adjust the values of the power factor correction capacitors.
To prevent voltage instability and voltage transients it is recommended that
power factor correction capacapacitor banks should be disabled when only the standby generation is running.

Answer / sudip sengupta

DG's are normally designed for P.F. of 0.8 lag. If the P.F.
of the load is more than 0.8, we should not use capacitor
bank as the current draws by the capacitor will increase
the KW demand of the DG. But if the load has P.F. less than
0.8, we can use capacitor bank to improve it to 0.8 or
slightly above.

Answer / sachin e jagtap

in case of generating stations,where few critical loads
need to be made ON ,DG set by its own capacity can supply
current n voltage to load but in case of distribution
substation where in case load requirement is not met by DG
alone ,we require capacitor banks also.

Answer / ravikant sahu

My dear frnds ,when DG set running ideal mode there is AVR
(Automatic Voltage Regulator)wich maintaine its voltage &
power factor according to load.So i think there don't want
any other capacitor bank.

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