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
230 VloadP = 483 W3.5 A

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 230 V, 3.5 A and 483 W. Find the reactive power Q taken by the load.

V = 230 VI = 3.5 AP = 483 W
Q = var
2.Easy
230 VloadP = 4140 W20 A

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 230 V, 20 A and 4140 W. Find the reactive power Q taken by the load.

V = 230 VI = 20 AP = 4140 W
Q = var
3.Medium
400 V13 kW, 0.65228 kW, 0.9I = ?

Two loads are connected in parallel to a 400 V single-phase supply: a 3 kW load at a power factor of 0.65 lagging and a 28 kW load at a power factor of 0.9 lagging. Find the total current I drawn from the supply.

V = 400 VP1 = 3 kW, pf1 = 0.65 laggingP2 = 28 kW, pf2 = 0.9 lagging
I = A
4.Medium
P = 39 kWQ = ?Sφ

A single-phase motor takes 39 kW at a power factor of 0.8 lagging from a 230 V supply. Find the reactive power Q it draws.

P = 39 kWpf = 0.8V = 230 V
Q = kvar
5.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 0.95. Find the capacitance C needed.

P = 25 kWpf1 = 0.7pf2 = 0.95V = 240 Vf = 60 Hz
C = µF
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 240 V, 50 Hz supply. A capacitor connected in parallel raises the power factor to 0.95. Find the reactive power QC the capacitor must supply.

P = 15 kWpf1 = 0.65pf2 = 0.95V = 240 Vf = 50 Hz
QC = kvar

Answer key

  1. 1. Q = 644 var
  2. 2. Q = 2005 var
  3. 3. I = 88.47 A
  4. 4. Q = 29.25 kvar
  5. 5. C = 796.1 µF
  6. 6. QC = 12.61 kvar

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