I am calculating a capacitor bank for a motor panel that have several motors. But these motors have different ratings and different power factors as well. Shall I use the worst power factor for all loadings or by ratio method?

 

You can have an automatic power factor controller with variable steps of Capacitors connected in steps put together to meet the maximum load.

By this you can optimise the Power factor maintenance charges.

Mohankumar

 

As you have variable rated motors you can go for an automatic power factor controller with various capacitors connected in various steps of 1 KVAR, 2 KVAR,3 KVAR, 5 KVAR .... up to the maximum capacitor value required with the combination of the individual capacitors.

With this you can optimise the Power costs.

 

hi stephen,
you should use automatic power factor controller ( available in market ) .
if you will use so then you can consider worst power factor. otherwise you
should average power factor for optimum result.

Regards,
Shailesh C Patel
FDC - Control Systems And Instrumentation

 

Add up the KVAR requirement for all of the motors, divide it by the maximum number of steps (8-10) available on the APFC controller and purchase the nearest standard size of capacitors. Maintenance will be easier at a later date as only one size of capacitors need to be stocked.

Tomy Zacharia

 

Responding to S. Cheung's May 19, 12:21 am query:

If energy metering is, or can be made available, then the capacitor value required to achieve any desired power factor can be easily determined!

Contact me for details.

Regards,
Phil Corso, PE {Boca Raton, FL, USA}
[[email protected]] ([email protected])