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​ = 250N2​ = 6250690 VV2​ = ?

An ideal transformer has 250 turns on its primary winding and 6250 turns on its secondary winding. The primary is connected to a 690 V AC supply. Find the secondary voltage V2.

N1 = 250N2 = 6250V1 = 690 V
V2 = V
2.Easy
N1​ = 800N2​ = 200920 VV2​ = ?

An ideal transformer has 800 turns on its primary winding and 200 turns on its secondary winding. The primary is connected to a 920 V AC supply. Find the secondary voltage V2.

N1 = 800N2 = 200V1 = 920 V
V2 = V
3.Medium
7200 V240 VIHV​ = ?ILV​25 kVA

A single-phase 25 kVA, 7200/240 V transformer operates at its rated load. Treat it as ideal. Find the current IHV in the high-voltage winding.

S = 25 kVAV1 = 7200 VV2 = 240 V
IHV = A
4.Medium
RL​ = 48 Ω1011200 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 10:1 has 1200 V applied to its primary winding. A 48 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 10:1V1 = 1200 VRL = 48 Ω
I1 = A
5.Hard
pf 0.95150 kVA, 25% load

A single-phase 150 kVA transformer has a core loss of 750 W and a copper loss of 1500 W at rated load. It supplies 25% of its rated kVA at a power factor of 0.95 lagging. Find the total losses Ploss in watts at this load.

S = 150 kVAPcore = 750 WPcu,fl = 1500 Wx = 0.25pf = 0.95
Ploss = W
6.Hard
pf 0.925 kVA, 25% load

A single-phase 25 kVA transformer has a core loss of 150 W and a copper loss of 600 W at rated load. It supplies 25% of its rated kVA at a power factor of 0.9 lagging. Find the total losses Ploss in watts at this load.

S = 25 kVAPcore = 150 WPcu,fl = 600 Wx = 0.25pf = 0.9
Ploss = W

Answer key

  1. 1. V2 = 17250 V
  2. 2. V2 = 230 V
  3. 3. IHV = 3.472 A
  4. 4. I1 = 0.25 A
  5. 5. Ploss = 843.8 W
  6. 6. Ploss = 187.5 W

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