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​ = 2500N2​ = ?20000 V400 V

An ideal transformer must step 20000 V down to 400 V. Its primary winding has 2500 turns. How many turns N2 does the secondary winding need?

V1 = 20000 VV2 = 400 VN1 = 2500
N2 =
2.Easy
N1​ = 960N2​ = 601920 VV2​ = ?

An ideal transformer has 960 turns on its primary winding and 60 turns on its secondary winding. The primary is connected to a 1920 V AC supply. Find the secondary voltage V2.

N1 = 960N2 = 60V1 = 1920 V
V2 = V
3.Medium
RL​ = 10 Ω41480 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 4:1 has 480 V applied to its primary winding. A 10 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 4:1V1 = 480 VRL = 10 Ω
I1 = A
4.Medium
2400 V240 VIHV​ = ?ILV​250 kVA

A single-phase 250 kVA, 2400/240 V transformer operates at its rated load. Treat it as ideal. Find the current IHV in the high-voltage winding.

S = 250 kVAV1 = 2400 VV2 = 240 V
IHV = A
5.Hard
pf 0.8250 kVA, 25% load

A single-phase 250 kVA transformer has a core loss of 750 W and a copper loss of 1875 W at rated load. It supplies 25% of its rated kVA at a power factor of 0.8 lagging. Find the total losses Ploss in watts at this load.

S = 250 kVAPcore = 750 WPcu,fl = 1875 Wx = 0.25pf = 0.8
Ploss = W
6.Hard
pf 0.8250 kVA, η = 97.5%

A single-phase 250 kVA transformer has a core loss of 1250 W. At rated load and a power factor of 0.8 lagging its efficiency is 97.5%. Find the full-load copper loss Pcu,fl in watts.

S = 250 kVAPcore = 1250 Wpf = 0.8η = 97.5%
Pcu,fl = W

Answer key

  1. 1. N2 = 50
  2. 2. V2 = 120 V
  3. 3. I1 = 3 A
  4. 4. IHV = 104.2 A
  5. 5. Ploss = 867.2 W
  6. 6. Pcu,fl = 3878 W

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