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 11 A (rms) from a 230 V (rms) supply at a power factor of 0.85 lagging. Find the reactive power Q it takes.

V = 230 VI = 11 Apf = cos φ = 0.85
Q = var
2.Easy
240 Vload9.5 kW, 5 kvarI = ?

A single-phase load connected to a 240 V supply takes 9.5 kW and 5 kvar. Find the current I drawn from the supply.

V = 240 VP = 9.5 kWQ = 5 kvar
I = A
3.Medium
P = 3 kWQ = ?Sφ

A single-phase motor takes 3 kW at a power factor of 0.6 lagging from a 230 V supply. Find the reactive power Q it draws.

P = 3 kWpf = 0.6V = 230 V
Q = kvar
4.Medium
P = 36 kWQ = ?Sφ

A single-phase motor takes 36 kW at a power factor of 0.7 lagging from a 240 V supply. Find the reactive power Q it draws.

P = 36 kWpf = 0.7V = 240 V
Q = kvar
5.Hard
P = 50 kWQ1​S1​φ1​QC​

A single-phase load takes 50 kW at a power factor of 0.65 lagging from a 230 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.95. Find the new line current Inew.

P = 50 kWpf1 = 0.65pf2 = 0.95V = 230 Vf = 60 Hz
Inew = A
6.Hard
400 V60 Hzload22 kW, 0.8C220 µFI = ?

A single-phase load takes 22 kW at a power factor of 0.8 lagging from a 400 V, 60 Hz supply. A 220 µF capacitor is connected in parallel with the load. Find the new line current I.

P = 22 kWpf1 = 0.8V = 400 Vf = 60 HzC = 220 µF
I = A

Answer key

  1. 1. Q = 1333 var
  2. 2. I = 44.73 A
  3. 3. Q = 4 kvar
  4. 4. Q = 36.73 kvar
  5. 5. Inew = 228.8 A
  6. 6. I = 55.59 A

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