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 = 2944 W16 A

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 230 V, 16 A and 2944 W. Find the reactive power Q taken by the load.

V = 230 VI = 16 AP = 2944 W
Q = var
2.Easy
P = ?QS = V·Iφ

A single-phase load draws 12 A (rms) from a 400 V (rms) supply at a power factor of 0.8 lagging. Find the real power P it takes.

V = 400 VI = 12 Apf = cos φ = 0.8
P = W
3.Medium
P = 23 kWQ = ?Sφ

A single-phase motor takes 23 kW at a power factor of 0.7 lagging from a 230 V supply. Find the reactive power Q it draws.

P = 23 kWpf = 0.7V = 230 V
Q = kvar
4.Medium
P = 20 kWQSφ

A single-phase motor takes 20 kW at a power factor of 0.6 lagging from a 240 V supply. Find the line current I.

P = 20 kWpf = 0.6V = 240 V
I = A
5.Hard
P = 40 kWQ1​S1​φ1​QC​

A single-phase load takes 40 kW at a power factor of 0.75 lagging from a 240 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.98. Find the new line current Inew.

P = 40 kWpf1 = 0.75pf2 = 0.98V = 240 Vf = 60 Hz
Inew = A
6.Hard
240 V50 Hzload26 kW, 0.75C330 µFI = ?

A single-phase load takes 26 kW at a power factor of 0.75 lagging from a 240 V, 50 Hz supply. A 330 µF capacitor is connected in parallel with the load. Find the new line current I.

P = 26 kWpf1 = 0.75V = 240 Vf = 50 HzC = 330 µF
I = A

Answer key

  1. 1. Q = 2208 var
  2. 2. P = 3840 W
  3. 3. Q = 23.46 kvar
  4. 4. I = 138.9 A
  5. 5. Inew = 170.1 A
  6. 6. I = 129.3 A

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