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
PQ = ?S = V·Iφ

A single-phase load draws 12 A (rms) from a 240 V (rms) supply at a power factor of 0.7 lagging. Find the reactive power Q it takes.

V = 240 VI = 12 Apf = cos φ = 0.7
Q = var
2.Easy
PQ = ?S = V·Iφ

A single-phase load draws 20 A (rms) from a 120 V (rms) supply at a power factor of 0.7 lagging. Find the reactive power Q it takes.

V = 120 VI = 20 Apf = cos φ = 0.7
Q = var
3.Medium
P = 7 kWQ = ?Sφ

A single-phase motor takes 7 kW at a power factor of 0.75 lagging from a 230 V supply. Find the reactive power Q it draws.

P = 7 kWpf = 0.75V = 230 V
Q = kvar
4.Medium
P = 29 kWQ = ?Sφ

A single-phase motor takes 29 kW at a power factor of 0.9 lagging from a 230 V supply. Find the reactive power Q it draws.

P = 29 kWpf = 0.9V = 230 V
Q = kvar
5.Hard
P = 35 kWQ1​S1​φ1​QC​

A single-phase load takes 35 kW at a power factor of 0.65 lagging from a 240 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.92. Find the new line current Inew.

P = 35 kWpf1 = 0.65pf2 = 0.92V = 240 Vf = 60 Hz
Inew = A
6.Hard
P = 15 kWQ1​S1​φ1​QC​

A single-phase load takes 15 kW at a power factor of 0.65 lagging from a 230 V, 50 Hz supply. A capacitor connected in parallel raises the power factor to 0.95. Find the new line current Inew.

P = 15 kWpf1 = 0.65pf2 = 0.95V = 230 Vf = 50 Hz
Inew = A

Answer key

  1. 1. Q = 2057 var
  2. 2. Q = 1714 var
  3. 3. Q = 6.173 kvar
  4. 4. Q = 14.05 kvar
  5. 5. Inew = 158.5 A
  6. 6. Inew = 68.65 A

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