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 Vload14 kW, 14.5 kvarI = ?

A single-phase load connected to a 400 V supply takes 14 kW and 14.5 kvar. Find the current I drawn from the supply.

V = 400 VP = 14 kWQ = 14.5 kvar
I = A
2.Easy
P = 48 kWQ = 32 kvarS = ?φ

A load takes 48 kW of real power and 32 kvar of reactive power (lagging). Find the apparent power S.

P = 48 kWQ = 32 kvar
S = kVA
3.Medium
P = 37 kWQ = ?Sφ

A single-phase motor takes 37 kW at a power factor of 0.8 lagging from a 230 V supply. Find the reactive power Q it draws.

P = 37 kWpf = 0.8V = 230 V
Q = kvar
4.Medium
P = 27 kWQSφ

A single-phase motor takes 27 kW at a power factor of 0.9 lagging from a 240 V supply. Find the line current I.

P = 27 kWpf = 0.9V = 240 V
I = A
5.Hard
P = 30 kWQ1​S1​φ1​QC​

A single-phase load takes 30 kW at a power factor of 0.6 lagging from a 240 V, 50 Hz supply. A capacitor connected in parallel raises the power factor to 0.92. Find the capacitance C needed.

P = 30 kWpf1 = 0.6pf2 = 0.92V = 240 Vf = 50 Hz
C = µF
6.Hard
P = 5 kWQ1​S1​φ1​QC​

A single-phase load takes 5 kW at a power factor of 0.7 lagging from a 400 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.9. Find the reactive power QC the capacitor must supply.

P = 5 kWpf1 = 0.7pf2 = 0.9V = 400 Vf = 60 Hz
QC = kvar

Answer key

  1. 1. I = 50.39 A
  2. 2. S = 57.69 kVA
  3. 3. Q = 27.75 kvar
  4. 4. I = 125 A
  5. 5. C = 1504 µF
  6. 6. QC = 2.679 kvar

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