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
240 Vload16.5 kW, 7 kvarI = ?

A single-phase load connected to a 240 V supply takes 16.5 kW and 7 kvar. Find the current I drawn from the supply.

V = 240 VP = 16.5 kWQ = 7 kvar
I = A
2.Easy
P = ?QS = V·Iφ

A single-phase load draws 15 A (rms) from a 240 V (rms) supply at a power factor of 0.85 lagging. Find the real power P it takes.

V = 240 VI = 15 Apf = cos φ = 0.85
P = W
3.Medium
P = 11 kWQSφ

A single-phase motor takes 11 kW at a power factor of 0.75 lagging from a 230 V supply. Find the line current I.

P = 11 kWpf = 0.75V = 230 V
I = A
4.Medium
P = 33 kWQSφ

A single-phase motor takes 33 kW at a power factor of 0.75 lagging from a 400 V supply. Find the line current I.

P = 33 kWpf = 0.75V = 400 V
I = A
5.Hard
P1​ = 93 kWQ1​S1​φ

A 200 kVA single-phase transformer supplies a load of 93 kW at a power factor of 0.75 lagging. How much extra real power ΔP can be added as a resistive (unity power factor) load before the transformer reaches its kVA rating?

Smax = 200 kVAP1 = 93 kWpf1 = 0.75
ΔP = kW
6.Hard
P = 10 kWQ1​S1​φ1​QC​

A single-phase load takes 10 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 0.9. Find the new line current Inew.

P = 10 kWpf1 = 0.6pf2 = 0.9V = 240 Vf = 60 Hz
Inew = A

Answer key

  1. 1. I = 74.68 A
  2. 2. P = 3060 W
  3. 3. I = 63.77 A
  4. 4. I = 110 A
  5. 5. ΔP = 89.41 kW
  6. 6. Inew = 46.3 A

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