# Power Factor

### #1

Posted 20 January 2005 - 09:57 AM

120VAC

0.6Amps

Is this the correct way to calculate it?

120Vx0.6A=72Watts

0.6Ax120V=72VA

72W/72VA=1 PF=1 Is this right?

### #2

Posted 20 January 2005 - 05:46 PM

Welcome to the forum.

Power factor is the ratio of KW to KVA. i.e. pf = KW/KVA.

V x I = VA

V x I x PF = Watts

You can calculate the power factor provided that you know the volts, Amps and KW. You can not calculate PF from volts and amps only.

There are two forms of power factor, one is displacement power factor, caused by reactive loads (typically inductive) and the other is harmonic power factor caused by solid state loads such as computers and VSDs.

If you have an inductive load such as a motor, you can use an oscilloscope to measure the phase angle between the voltage and the current and calculate the displacement power factor from the cosine of the displacement angle.

Unfortunately, you need more measurements than just a voltmeter and ameter.

Best regards,

Mark Empson | administrator

Skype Contact = markempson | phone +64 274 363 067

LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters

### #3 Guest__*

Posted 02 September 2005 - 11:58 AM

Phi is the angle between voltage and ampear

PF = Watt / VA

PF = R / Z = R / (R+jX)

### #4

Posted 03 September 2005 - 07:57 AM

PF = KW/KVA is more correct.

Best regards,

Mark Empson | administrator

Skype Contact = markempson | phone +64 274 363 067

LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters

### #5 Guest__*

Posted 17 November 2005 - 06:38 AM

Subject Power factor

I will not say more than u all said but there are still something missing in the calculation cause it is not only a matter of power p.f=W/VA

so if some one know he can right more specified explanation

### #6

Posted 17 November 2005 - 08:30 AM

This is true for displacement power factor and distortion power factor.

Displacement power factor can also be expressed as pf = cos(thi) where thi is the angle between voltage and current.

Best regards,

Mark Empson | administrator

Skype Contact = markempson | phone +64 274 363 067

LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters

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