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Low Power Factor in Phase Y & B


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#1 Guest__*

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Posted 29 August 2005 - 02:35 PM

Dear All,

I have experiences a real problem in an electrical system which the power factor between phases having a bit large differences. (i.e. Phase R = 0.95, Phase Y = 0.7, Phase B = 0.6) This electrical system supplies to a two phase loading.

Is it possible for us to install a 3-phase delta capacitor bank but disconnect the red phase contactor ? or using single phase capacitor for phase Y and B?

Because I'm afraid we will overcompensate to the red phase if a traditional capacitor is applied.


Thanks for your help in advance.

Best Regards,

Peter

#2 marke

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Posted 29 August 2005 - 07:16 PM

Hello Peter

The easiest way to correct your system is to apply static correction to each load that is contributing to a displacement power factor. Correct in the same manner that the load is applied, i.e. 2 phase etc by connecting appropriate capacitors across the supply at the load connection using separate contactors.
Ensure that motors are only staticaly corrected to 80% of their magnetising current.
Additional correction can be applied at the point of supply.

Where there is two phase connected load in addition to three phase connected load, you will have a unbalanced power factor due to the fact that the corrected current flowing through the two phase load will be in phase with the applied voltage (tow phases and this will be 30 degrees away from the phase neutral voltage. Relative to neutral, on phase will lead by 30 degres and one phase will lag, but you will have minimised the current if the correction is correctly applied as you will have cancelled out the VARs current.

Best regards,

#3 Guest__*

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Posted 04 September 2005 - 02:07 PM

Thank you Marke. Is it possible to install a capacitor bank and disable its contactor on the phase that are not connected to a two phase load as attached sketch ?

Best Regards,

Peter

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