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 2400 turns on its primary winding and 60 turns on its secondary winding. The primary is connected to a 4800 V AC supply. Find the secondary voltage V₂.

N₁ = 2400N₂ = 60V₁ = 4800 V

V₂ = V

2.Easy

An ideal transformer must step 960 V down to 120 V. Its primary winding has 800 turns. How many turns N₂ does the secondary winding need?

V₁ = 960 VV₂ = 120 VN₁ = 800

N₂ =

3.Medium

A single-phase 25 kVA, 6600/230 V transformer operates at its rated load. Treat it as ideal. Find the current I_HV in the high-voltage winding.

S = 25 kVAV₁ = 6600 VV₂ = 230 V

I_HV = A

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 10:1 has 1200 V applied to its primary winding. A 24 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 10:1V₁ = 1200 VR_L = 24 Ω

I₁ = A

5.Hard

A single-phase 150 kVA transformer has a core loss of 900 W and a copper loss of 1800 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 150 kVAP_core = 900 WP_cu,fl = 1800 W

S_η,max = kVA

6.Hard

A single-phase 250 kVA transformer has a core loss of 2000 W. At rated load and a power factor of 0.9 lagging its efficiency is 96%. Find the full-load copper loss P_cu,fl in watts.

S = 250 kVAP_core = 2000 Wpf = 0.9η = 96%

P_cu,fl = W

Answer key

1. V₂ = 120 V
2. N₂ = 100
3. I_HV = 3.788 A
4. I₁ = 0.5 A
5. S_η,max = 106.1 kVA
6. P_cu,fl = 7375 W

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