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
400 Vload27.5 kW, 20.5 kvarI = ?

A single-phase load connected to a 400 V supply takes 27.5 kW and 20.5 kvar. Find the current I drawn from the supply.

V = 400 VP = 27.5 kWQ = 20.5 kvar
I = A
2.Easy
P = ?QS = V·Iφ

A single-phase load draws 20 A (rms) from a 240 V (rms) supply at a power factor of 0.9 lagging. Find the real power P it takes.

V = 240 VI = 20 Apf = cos φ = 0.9
P = W
3.Medium
P = 21 kWQSφ

A single-phase motor takes 21 kW at a power factor of 0.6 lagging from a 240 V supply. Find the line current I.

P = 21 kWpf = 0.6V = 240 V
I = A
4.Medium
P = 18 kWQSφ

A single-phase motor takes 18 kW at a power factor of 0.65 lagging from a 230 V supply. Find the line current I.

P = 18 kWpf = 0.65V = 230 V
I = A
5.Hard
P = 50 kWQ1​S1​φ1​QC​

A single-phase load takes 50 kW at a power factor of 0.75 lagging from a 240 V, 50 Hz supply. A capacitor connected in parallel raises the power factor to 0.98. Find the new line current Inew.

P = 50 kWpf1 = 0.75pf2 = 0.98V = 240 Vf = 50 Hz
Inew = A
6.Hard
P = 30 kWQ1​S1​φ1​QC​

A single-phase load takes 30 kW at a power factor of 0.65 lagging from a 400 V, 50 Hz supply. A capacitor connected in parallel raises the power factor to 0.98. Find the reactive power QC the capacitor must supply.

P = 30 kWpf1 = 0.65pf2 = 0.98V = 400 Vf = 50 Hz
QC = kvar

Answer key

  1. 1. I = 85.75 A
  2. 2. P = 4320 W
  3. 3. I = 145.8 A
  4. 4. I = 120.4 A
  5. 5. Inew = 212.6 A
  6. 6. QC = 28.98 kvar

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