Re: Power Factor In Depth

Spir Georges GHALI

Dear Mr. Steven ;

First, it’s a good subject to be discussed but certainly not the principal basics as mentioned, because all Electrical Engineers should absolutely know it.

Let me please mention to the following points:


Leading and Lagging Power Factor :

  • When mentioned “ Voltage phaser or Current phaser ” that means “ Voltage Vector  or  Current Vector ” .
  • When you say “ we add capacitance to our system to minimize inductance and vice versa ”, you certainly mean that we add the capacitance to have a capacitive current that will minimize the inductive current ”.


Active Power and Reactive Power :

  • The 2 formulas are mentioned to the “ Active Power ” where the 2nd should be :

 “ Reactive Power : V(rms)I(rms)sin(angle between V and I)

  • It’s mentioned that “ both inductor and capacitor (pure) are lossless elements means that they don’t consume any   power they only cause voltage drop across themselves”, but sorry to say : electrically it’s not right, because when there’s a drop voltage, that means there’s a current runs in the circuit, and if there’s a current that means there’s a Power’s consumption. By another wards:

    • All “ pure Capacitive or pure Inductive loads consume a Reactive Power ”.
    • The Reactive Power is a kind of power without obtaining a useful work.
    •  It’s mentioned also that “ They only absorb power from the source and release it after wards ” and “ Thus Reactive power oscillates or moves to and forth in the circuit … ”, but sorry to say : electrically it’s not right, they absorb ( consume ) power but they don’t release it, and also the absorbed Reactive Power doesn’t oscillate or move to and forth in the circuit.


Power Factor (Practically) :

To be more clear, the relation between the “ Cos ϕ ” ( Power Factor for the Fundamental Voltage and Current ) and the Power Factor for Network containing Harmonics ( Polluted Network ) is done by the following formula :

Power Factor = Cos φ / √(1+THD I²) 

Where the “ THD I ” is the Total Harmonic Distortion of Current.

So, relative to your formula the Distortion Factor is : 1/√(1+THD I²)