AC power & power factor worksheet with answers

Free printable AC power & power factor worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

A single-phase load draws 20 A (rms) from a 400 V (rms) supply at a power factor of 0.85 lagging. Find the real power P it takes.

V = 400 VI = 20 Apf = cos φ = 0.85

P = W

2.Easy

A single-phase load connected to a 240 V supply takes 29 kW and 14 kvar. Find the current I drawn from the supply.

V = 240 VP = 29 kWQ = 14 kvar

I = A

3.Medium

A single-phase motor takes 13 kW at a power factor of 0.75 lagging from a 230 V supply. Find the line current I.

P = 13 kWpf = 0.75V = 230 V

I = A

4.Medium

A load with impedance Z = 5 + j12 Ω is connected to a 240 V (rms) single-phase supply. Find the reactive power Q it absorbs.

V = 240 VZ = 5 + j12 Ω

Q = var

5.Hard

A single-phase load takes 40 kW at a power factor of 0.6 lagging from a 400 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.95. Find the capacitance C needed.

P = 40 kWpf₁ = 0.6pf₂ = 0.95V = 400 Vf = 60 Hz

C = µF

6.Hard

A single-phase load takes 40 kW at a power factor of 0.6 lagging from a 240 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.98. Find the capacitance C needed.

P = 40 kWpf₁ = 0.6pf₂ = 0.98V = 240 Vf = 60 Hz

C = µF

Answer key

1. P = 6800 W
2. I = 134.2 A
3. I = 75.36 A
4. Q = 4090 var
5. C = 666.2 µF
6. C = 2082 µF

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