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 worksheet Practise 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

An ideal transformer has 160 turns on its primary winding and 20 turns on its secondary winding. The primary is connected to a 1920 V AC supply. Find the secondary voltage V₂.

N₁ = 160N₂ = 20V₁ = 1920 V

V₂ = V

2.Easy

An ideal transformer has 100 turns on its primary winding and 2500 turns on its secondary winding. The primary is connected to a 240 V AC supply. Find the secondary voltage V₂.

N₁ = 100N₂ = 2500V₁ = 240 V

V₂ = V

3.Medium

A single-phase 25 kVA, 480/240 V transformer operates at its rated load. Treat it as ideal. Find the current I_HV in the high-voltage winding.

S = 25 kVAV₁ = 480 VV₂ = 240 V

I_HV = A

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 5:1 has 600 V applied to its primary winding. A 4 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 5:1V₁ = 600 VR_L = 4 Ω

I₁ = A

5.Hard

A single-phase 25 kVA transformer has a core loss of 150 W. At rated load and a power factor of 0.95 lagging its efficiency is 97.5%. Find the full-load copper loss P_cu,fl in watts.

S = 25 kVAP_core = 150 Wpf = 0.95η = 97.5%

P_cu,fl = W

6.Hard

A single-phase 25 kVA transformer has a core loss of 150 W and a copper loss of 300 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 25 kVAP_core = 150 WP_cu,fl = 300 W

S_η,max = kVA

Answer key

1. V₂ = 240 V
2. V₂ = 6000 V
3. I_HV = 52.08 A
4. I₁ = 6 A
5. P_cu,fl = 459 W
6. S_η,max = 17.68 kVA

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