Jump to content


Can Power Factor Exceed Unity?


  • Please log in to reply
9 replies to this topic

#1 Guest_msb_*

Guest_msb_*
  • Guests

Posted 17 January 2006 - 07:09 AM

Hi,

Our last power bill shows the PF as 2.38. Is this at all theoretically/practically possible? Or is it probably a mistake in the meter reading?

In the previous bill it was 0.56.

We have now added an Automatic Power Factor controller.

#2 ram14375

ram14375

    Member

  • Full Member
  • PipPipPipPip
  • 61 posts

Posted 17 January 2006 - 05:05 PM

hi,
Power factor can never exceed unity as it is the ratio of active power to apparent power.it can go in leading or lagging not above unity at any case.
It should be the mistake of the meter. if u have power factor incentive you try to claim the same from your supplier for the above pf

#3 marke

marke

    Posting Freak

  • Moderator
  • PipPipPipPipPipPip
  • 2,604 posts
  • Gender:Male
  • Location:Christchurch, New Zealand

Posted 17 January 2006 - 06:05 PM

Hello msb

I agree with ram14375.
Power factor is the ratio between KW and KVA and it is not possible for this to exceed 1. If it did, we would all do it and be making money!!

Distortion power factor is always less than or equal to one, and displacment power factor can be positive or negative and is in the range of -1 to +1.

Best regards,

#4 Guest_msb_*

Guest_msb_*
  • Guests

Posted 18 January 2006 - 05:26 AM

Thanks for your replies. I just checked the energy meter and the readings are as following:

PF1 = 0.92
PF2 = -0.99

What does the negative reading mean? Is this normal or are my capacitors wired in wrong? How do I rectify this? Thanks in advance.

#5 marke

marke

    Posting Freak

  • Moderator
  • PipPipPipPipPipPip
  • 2,604 posts
  • Gender:Male
  • Location:Christchurch, New Zealand

Posted 18 January 2006 - 05:57 AM

Hello msb

Generally, an inductive power factor is positive and a capacitive power factor is negative. If there is a problem with the ct connections, you can get a negative pf reading.

A capacitive power factor means that you have applied too much capacitance. In a bulk corection installation, this is not usually a problem, however in a static corection case, this is potentially very dangerous.
Reduce tha amount of capacitance, and the pf should go positive.

Best regards,

#6 chris1373

chris1373

    Intermediate Member

  • Full Member
  • PipPipPip
  • 31 posts

Posted 28 August 2007 - 06:38 PM

What is the diference betwin a "bulk correction" and a "static correction"?

Thanks.
Chris.

QUOTE(marke @ Jan 18 2006, 05:57 AM) View Post

Hello msb
Generally, an inductive power factor is positive and a capacitive power factor is negative. If there is a problem with the ct connections, you can get a negative pf reading.
A capacitive power factor means that you have applied too much capacitance. In a bulk corection installation, this is not usually a problem, however in a static corection case, this is potentially very dangerous.
Reduce tha amount of capacitance, and the pf should go positive.
Best regards,


#7 marke

marke

    Posting Freak

  • Moderator
  • PipPipPipPipPipPip
  • 2,604 posts
  • Gender:Male
  • Location:Christchurch, New Zealand

Posted 28 August 2007 - 07:08 PM

Hello Chris

Check out http://www.lmphotonics.com/pwrfact.htm which gives descriptions of static and bulk correction.
Essentially, static correction is applied to each motor and is controlled by the motor starter, and bulk correction is applied at the point of supply, submain or similar and is controlled by an automatic controller.

Best regards,

#8 ravi agnihotri

ravi agnihotri

    Junior Member

  • Members
  • PipPip
  • 3 posts

Posted 31 August 2007 - 03:13 PM

QUOTE(msb @ Jan 17 2006, 12:39 PM) View Post

Hi,
Our last power bill shows the PF as 2.38. Is this at all theoretically/practically possible? Or is it probably a mistake in the meter reading?
In the previous bill it was 0.56.
We have now added an Automatic Power Factor controller.



#9 ravi agnihotri

ravi agnihotri

    Junior Member

  • Members
  • PipPip
  • 3 posts

Posted 31 August 2007 - 03:18 PM

basically power factor=real power/ apparent power

real power= voltage*current*cos@ =v*i*cos@

apparent power= v*i

so, power factor = (v*i*cos@)/(v*i)
=cos@

& we know that max value of cosine can naver exceed unity..........
so power factor can never be more than 1.


#10 marke

marke

    Posting Freak

  • Moderator
  • PipPipPipPipPipPip
  • 2,604 posts
  • Gender:Male
  • Location:Christchurch, New Zealand

Posted 31 August 2007 - 09:57 PM

Hello ravi agnihotri

This is true if you are considering displacement power factor.
The Cosine does not apply to distortion power factor, but the outcome is the same, power factor can not be greater than 1.

Best regards,




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users