Three-phase power worksheet with answers

Free printable Three-phase power worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

New worksheetPractise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________   Date: ____________

1.Easy
ABCVL​ = 400 VIL​ = ?NZ = 18 + j24 Ωper phase

A balanced Y-connected load has an impedance of 18 + j24 Ω per phase. It is supplied from a balanced three-phase source with a line-to-line voltage of 400 V. Find the magnitude of the line current IL.

VL = 400 VZ = 18 + j24 Ω per phase
IL = A
2.Easy
ABCVL​ = 400 VZ = 6 + j8 Ωper phase

A balanced Δ-connected load has an impedance of 6 + j8 Ω per phase. It is supplied from a balanced three-phase source with a line-to-line voltage of 400 V. Find the magnitude of the phase current Iph flowing through each impedance.

VL = 400 VZ = 6 + j8 Ω per phase
Iph = A
3.Medium
ABCVL​ = 208 VZ = 12 + j9 Ωper phase

A balanced Δ-connected load with an impedance of 12 + j9 Ω per phase is connected to a balanced three-phase supply with a line-to-line voltage of 208 V. Find the total real power P absorbed by the load in kW.

VL = 208 VZ = 12 + j9 Ω per phase
P = kW
4.Medium
ABCVL​ = 400 VZ = 16 + j12 Ωper phase

A balanced Δ-connected load with an impedance of 16 + j12 Ω per phase is connected to a balanced three-phase supply with a line-to-line voltage of 400 V. Find the total real power P absorbed by the load in kW.

VL = 400 VZ = 16 + j12 Ω per phase
P = kW
5.Hard
P = 100 kWφ1​S1​Q2​QC​

A balanced three-phase load takes 100 kW at a power factor of 0.7 lagging from a 690 V (line-to-line), 50 Hz supply. A three-phase capacitor bank in parallel with the load must raise the overall power factor to 0.98 lagging. The real power stays the same. The capacitors are connected in Y. Find the capacitance Cph of each capacitor in µF.

P = 100 kWpf1 = 0.7pf2 = 0.98VL = 690 Vf = 50 Hz
Cph = µF
6.Hard
P = 60 kWφ1​S1​Q2​QC​

A balanced three-phase load takes 60 kW at a power factor of 0.65 lagging from a 415 V (line-to-line), 50 Hz supply. A three-phase capacitor bank in parallel with the load must raise the overall power factor to 0.9 lagging. The real power stays the same. The capacitors are connected in Y. Find the capacitance Cph of each capacitor in µF.

P = 60 kWpf1 = 0.65pf2 = 0.9VL = 415 Vf = 50 Hz
Cph = µF

Answer key

  1. 1. IL = 7.698 A
  2. 2. Iph = 40 A
  3. 3. P = 6.922 kW
  4. 4. P = 19.2 kW
  5. 5. Cph = 546.3 µF
  6. 6. Cph = 759.4 µF

Full step-by-step solutions: practise this topic on examproblems.com.