- It's is use to start the motor.
- It's improve reactive power.
- It's save money.
• Three phase Capacitor :
- It's is use to avoid the penalty from the government.
- It's rated with KVAR( kilo volt ampere reactance).
- Direction of reactive power is from load to source and the direction of active power is from source to load.
- For capacitive load, we convert a inductor to it.
- For inductive load, we convert a capacitor to it.
- For calculating capacitor is KVAR.
KVAR = KW{tan(cos¢1) - tan(cos¢2)}
¢1 - Present P.F.
¢2 - Required P.F.
• EXAMPLE :
10kw motor is at 0.6 P.F., we Required 0.95 P.F.
KVAR = KW {tan(cos¢1) - tan(cos¢2)}
= 10{tan(cos 0.6) - tan(cos 0.95)}
= 10{1.33 - 0.328}
= 10(1.002)
= 10.02
Therefore, 10.02KVAR is required
• Therefore, fixed and variable Capacitor are connected in APFC panel. But variable are connected through relay and fixed are always ON.
- To convert KVAR into Amper
KVAR × 2 = A
Whenever P.F. increase, Voltage will be increase and Current will be decreased.
• Example :
1000KVA transformer is given. Then, find out the capacitor size.
- For Capacitor, we have to select 40% of the transformer rating.
= 1000× 0.4 = 400KVAR
Where, 10% will be fixed and 30% will be variable.
1000 × 0.1 = 100 (fixed) KVAR
1000 × 0.3 = 300 (variable) KVAR
Rating of the capacitor is 0.25 KvAR to 50 KVAR.
- For fixed 100
We can take 50 × 2 = 100 KVAR
(50 KVAR 2 no.)
- For variable 300
We can take 50 × 6 = 300kVAR
(50 KVAR 6 no.)
Therefore, to select the amper we have to multiply by 2 to KVAR rating (or) 16 × 1.25
400 × 2 = 800A
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