All power factor improvment controller has a setting c/k ratio. Their manual says it is the lowest step of capacitor bank. It controls switching threshold. But how what is its significance?


\$C/K = \frac{Q }{I1/5A * U_{LL} * 1.73}\$

Where Q = Size of 1st step in VARs (Capacitor smallest step)
\$U_{LL}\$ = line-to-line voltage in volts
I1/5A = CT ratio

  • \$\begingroup\$ Why it is used as switching threshold? \$\endgroup\$ – xcoder Jan 11 '18 at 9:10
  • \$\begingroup\$ It is a control system gain ratio of negative reactance of cap VARs to positive reactance sensed by CT of inductive current loads such when this ratio is controlled PF is closer to unity and efficiency is improved. But when you change it is more complex \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 11 '18 at 11:44
  • \$\begingroup\$ In my pfi controller c/k is 0.13 & ct ratio 400/5. Does that mean capacitor step will change if inductive current change 0.13A? \$\endgroup\$ – xcoder Jan 11 '18 at 13:19
  • \$\begingroup\$ No this is a ratio, not in units of Amps. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 11 '18 at 14:05
  • \$\begingroup\$ Why I have to define this ratio to a controller. What it does with it? \$\endgroup\$ – xcoder Jan 11 '18 at 14:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.