AC2 Fundamentals Unit 4 – Power in AC Circuits
Exercise 2 – Power Factor
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to determine the power factor of ac
circuits by using standard electronic formulas. You will verify your results with an oscilloscope.
DISCUSSION
- A power triangle can be used to represent real power (P), reactive power (Q), and apparent
power (S). - Real power is drawn on the horizontal axis and represents the total real power in units of
watts. - Reactive power is represented on the vertical axis in units of vars.
- Apparent power is the resultant, or hypotenuse, of the triangle in units of VA.
- Power factor (PF) is a ratio of the circuit’s real power to the apparent power.
- The cosine of the angle (θ) equals the ratio of real power to apparent power and represents
the phase angle between the voltage and current of an ac circuit. - Apparent power multiplied by the power factor (cos θ) equals the real power of the ac circuit.
P = cos θ x S - Power factor defines what portion of the apparent power is real power.