When we change new power capacitor (PF Improvement)?

[kia]

When we change new power capacitor (PF Improvement)?

Ex. Cap 50 kVAR 400V Ir = 72.2 A Cab = 497.36 uF(Delta connection)

In catalogue shown -5% to +10% (Tolerance 472.5 - 547.1 uF)

- Why new cap have Capacitance more than calculated value?
Ex Ccal = 497.36 uF Cnew = 570 uF(more than 10%)

- When we change new power capacitor?
Cmeasured <= xx% of Ccal or Imeasured <= xx% of Ir

 

[alehman]

Are you calculating the capacitance using the same voltage as the rating of the capacitor?

 

[kia]

Yes, I calculate capacitance from capacitor rated.
In Delta loop had Cx, Cy and Cz,
So when we measure at terminal AB, Cab = Cx // (Cy + Cz)

at 50 kVAR 400V Cab = 497.36 uF