power factors

[admin]

dear i want knowledge about power factors

our load is 500 ampare

and and current power factors is 0.8

i want pf 0.98

plz tell me this calculation i wated

[erickench]

What is the voltage?

Is the power factor lagging or leading?

Is the power being taken from a generator or a transformer?

[su]

I think this voltage is 3phase(380V or 440V)

[Spir Georges GHALI]

mehmood saleem said:

dear i want knowledge about power factors

our load is 500 ampare

and and current power factors is 0.8

i want pf 0.98

plz tell me this calculation i wated

---

Dear ;

 

To ba able to calculate the needed capacitors' power, we shoul know the voltage of the network.

Asune that's ” 400 V “, so, the calculation will be done as the following :

Q = P ( tg φ1   –    tg φ2 )

where :

     – P = 1.73 x 400 x 500 x 0.8 = 276800 W    or   276.8 kW

     – tg φ1 = 0.75      ( we found it  from Cos φ1 = 0.8 )

     – tg φ2 = 0.203    ( we found it  from Cos φ2 = 0.98 )

So :

Q = 276.8 ( 0.75  –  0.203 ) = 151.4 kVAR

That's the power of capacitors that you need, but it's better to install more by 10-15%

 

Regards.

[manh_hoa09]

dear Spir Georges GHAL

According to your formulae, the compensation sysem only have capacitor. but It is only use for transmission gird and normal load. there are problem when use in industry plant which use a lot of big mortor or nonline load. We have to add reactor connect in series with capacitor, these reactor's function is protect capacitor. plz see the drawing in following:

But I don't know, with this compensator system, how do you caculate? how do you choose reactor?…ect

plz show me?

Thank you very much

[Spir Georges GHALI]

manh_hoa09 said:

dear Spir Georges GHAL

According to your formulae, the compensation sysem only have capacitor. but It is only use for transmission gird and normal load. there are problem when use in industry plant which use a lot of big mortor or nonline load. We have to add reactor connect in series with capacitor, these reactor's function is protect capacitor. plz see the drawing in following:

But I don't know, with this compensator system, how do you caculate? how do you choose reactor?…ect

plz show me?

Thank you very much

---

Dear ;

 

As before, we calculate first of all the needed capacitors power, then accordingly to the ” Poluation ” of the network, we can decide which kind of capacitors we should use, and we do that as follow :

     – We should calculate the percentage ” Gh / Sn ” where :

          – Gh : the total power in ” kVA ” for all equipments that generate the harmonics like : UPS, Variable Speed Drives, … ext.

          – Sn : the power in ” kVA ” of the tansformer.

then :

– If ” Gh/Sn = 0 … 15% ” : we can use the ” Standard Capacitors ” without any thing.

– If ” Gh/Sn > 15 … 25% ” : we should use the ” Overrated Capacitors ” without any reactors.

– If ” Gh/Sn > 25 … 50% ” : we should use the ” Detuned Capacitors ” that means ” Overrated Capacitors + Reactors “.

 

To define the type of reactors that we should use, as we have normally 3 types, we should analyze the network to know the existed harmonics, then the ” Tuning order ” for ” Reactors + Capacitors ” should be smaller than the smallest harmonic.

 

Rem. 1 : if you should use the Standars Capacitors, it will be better to know from the manufacture the percentage ” Gh/Sn ” that can withstand, because for some manufactures this percentage is ” 10% “.

 

Rem. 2 : if you should use the Detuned Capacitors, please be careful because the combination generates also some harmonics that we can know from the manufacture.

 

Regards.

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