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 Vload19 kW, 18.5 kvarI = ?

A single-phase load connected to a 400 V supply takes 19 kW and 18.5 kvar. Find the current I drawn from the supply.

V = 400 VP = 19 kWQ = 18.5 kvar
I = A
2.Easy
PQ = ?S = V·Iφ

A single-phase load draws 9 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 = 9 Apf = cos φ = 0.85
Q = var
3.Medium
P = 12 kWQSφ

A single-phase motor takes 12 kW at a power factor of 0.7 lagging from a 240 V supply. Find the line current I.

P = 12 kWpf = 0.7V = 240 V
I = A
4.Medium
230 VR + jXP = 2208 W16 A

An inductive load takes 16 A and 2208 W from a 230 V (rms) single-phase supply. Model it as a resistance R in series with a reactance X. Find X.

V = 230 VI = 16 AP = 2208 W
X = Ω
5.Hard
P = 10 kWQ1​S1​φ1​QC​

A single-phase load takes 10 kW at a power factor of 0.8 lagging from a 230 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.98. Find the capacitance C needed.

P = 10 kWpf1 = 0.8pf2 = 0.98V = 230 Vf = 60 Hz
C = µF
6.Hard
P = 25 kWQ1​S1​φ1​QC​

A single-phase load takes 25 kW at a power factor of 0.7 lagging from a 240 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.92. Find the capacitance C needed.

P = 25 kWpf1 = 0.7pf2 = 0.92V = 240 Vf = 60 Hz
C = µF

Answer key

  1. 1. I = 66.3 A
  2. 2. Q = 1090 var
  3. 3. I = 71.43 A
  4. 4. X = 11.5 Ω
  5. 5. C = 274.3 µF
  6. 6. C = 684.1 µF

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