What is the formula for Power Factor (PF)?

What is the formula for Power Factor (PF)?

• A. PF = KW / KVA
• B. PF = KW / KVAR
• C. PF = KVA / KW
• D. PF = KW / HP

Answer: (A)

Power factor is the ratio of real power to apparent power, showing how effectively electrical power is converted into useful work. Real power (P) in kilowatts is the power that does the work, while apparent power (S) in kilovolt-amperes is the combination of real and reactive power the system must supply. The relationship is PF = P / S, which in common units is PF = KW / KVA. This is also equal to cos φ, the phase angle between voltage and current. Why this form is the right one: it directly compares the useful power to the total power supplied. The other options mix different quantities or take a reciprocal, which doesn’t yield a dimensionless factor between 0 and 1. For example, KW / KVAR compares real power to reactive power and isn’t a measure of how much of the supplied power is usable; KVA / KW would be the reciprocal of PF, and KW / HP mixes power units rather than relating real to apparent power.

Power factor is the ratio of real power to apparent power, showing how effectively electrical power is converted into useful work. Real power (P) in kilowatts is the power that does the work, while apparent power (S) in kilovolt-amperes is the combination of real and reactive power the system must supply. The relationship is PF = P / S, which in common units is PF = KW / KVA. This is also equal to cos φ, the phase angle between voltage and current.

Why this form is the right one: it directly compares the useful power to the total power supplied. The other options mix different quantities or take a reciprocal, which doesn’t yield a dimensionless factor between 0 and 1. For example, KW / KVAR compares real power to reactive power and isn’t a measure of how much of the supplied power is usable; KVA / KW would be the reciprocal of PF, and KW / HP mixes power units rather than relating real to apparent power.