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What is Power Factor (Cosθ) ? Cos fi or P.f Definitions & Formulas

Power Factor (Cosθ) – Cos fi or P.f –

In electrical engineering, power factor is only and only related to AC circuits i.e. there is no power factor (P.f)  in DC circuits due to zero frequency.

What is Power Factor?

Power factor may be defined by three definitions and formals as follow.

1).  The Cosine of angle between Current and Voltage is called Power Factor.

Where:

  • P = Power in Watts
  • V = Voltages in Volts
  • I = Current in Amperes
  • W = Real Power in Watts
  • VA = Apparent Power in Volt-Amperes or Watts
  • Cosθ = Power factor

2). The ratio between resistance and Impedance is Called Power Factor.

Cosθ = R/Z

Where:

  • R = Resistnace in Ohms (Ω)
  • Z = Impedence (Resistance in AC circuits i.e. XL, XC and R known as Inductive reactance, capacitive reactance and resistance respectively) in Ohms (Ω)
  • Cosθ = Power factor

3).The ratio between Actual Power and Apparent Power is called power factor.

  • Cosθ = kW / kVA

Where

  • kW = Real Power in Watts
  • kVA = Apparent Power in Volt-Amperes or Watts
  • Cosθ = Power factor

Power Factor Triangle and Examples

What is Power Factor (Cosθ) ? Power Factor Triangle and Examples
Power Factor Triangle and Examples

Beer analogy of active or true power, reactive power, apparent power and power factor.

Beer analogy of active or true power, reactive power, apparent power and power factor.

Chips bag analogy of real or true power, reactive power, apparent power & power factor.

Chips bag analogy of real or true power, reactive power, apparent power & power factor.

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15 Comments

      1. That’s easy to understand!
        Now, what analogy can be given to a capacitor to show that even a capacitor is involved in the concept of Power Factor? It will give an even more clear understanding!

  1. the total power factor in actual is a product of the displacement power factor(cos[fi]) and the distortion power factor.the distortion power factor is a function of the total harmonic distortion,hence the total power factor of the system decreases on in actual practice on account of the presence of harmonics and other non linearities.

  2. sir plz answer the question its about control i know you can answer it …. which transform we use for convergence ? Laplace transform or Fourier transform or Z transform

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