Transformers worksheet with answers

Free printable Transformers 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
N1​ = 3200N2​ = ?3840 V240 V

An ideal transformer must step 3840 V down to 240 V. Its primary winding has 3200 turns. How many turns N2 does the secondary winding need?

V1 = 3840 VV2 = 240 VN1 = 3200
N2 =
2.Easy
N1​ = 120N2​ = 2400690 VV2​ = ?

An ideal transformer has 120 turns on its primary winding and 2400 turns on its secondary winding. The primary is connected to a 690 V AC supply. Find the secondary voltage V2.

N1 = 120N2 = 2400V1 = 690 V
V2 = V
3.Medium
50 ΩN1​N2​800 Ω

An amplifier with an output resistance of 800 Ω drives a 50 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 800 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

Rs = 800 ΩRL = 50 Ω
a =
4.Medium
4160 V480 VIHV​ILV​ = ?500 kVA

A single-phase 500 kVA, 4160/480 V transformer operates at its rated load. Treat it as ideal. Find the current ILV in the low-voltage winding.

S = 500 kVAV1 = 4160 VV2 = 480 V
ILV = A
5.Hard
pf 0.9500 kVA, η = 98%

A single-phase 500 kVA transformer has a core loss of 2500 W. At rated load and a power factor of 0.9 lagging its efficiency is 98%. Find the full-load copper loss Pcu,fl in watts.

S = 500 kVAPcore = 2500 Wpf = 0.9η = 98%
Pcu,fl = W
6.Hard
pf 0.8550 kVA, 25% load

A single-phase 50 kVA transformer has a core loss of 200 W and a copper loss of 600 W at rated load. It supplies 25% of its rated kVA at a power factor of 0.85 lagging. Find the total losses Ploss in watts at this load.

S = 50 kVAPcore = 200 WPcu,fl = 600 Wx = 0.25pf = 0.85
Ploss = W

Answer key

  1. 1. N2 = 200
  2. 2. V2 = 13800 V
  3. 3. a = 4
  4. 4. ILV = 1042 A
  5. 5. Pcu,fl = 6684 W
  6. 6. Ploss = 237.5 W

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