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 50 turns on its primary winding and 500 turns on its secondary winding. The primary is connected to a 240 V AC supply. Find the secondary voltage V₂.

N₁ = 50N₂ = 500V₁ = 240 V

V₂ = V

2.Easy

An ideal transformer must step 4800 V down to 120 V. Its primary winding has 2000 turns. How many turns N₂ does the secondary winding need?

V₁ = 4800 VV₂ = 120 VN₁ = 2000

N₂ =

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 4:1 has 920 V applied to its primary winding. A 40 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 4:1V₁ = 920 VR_L = 40 Ω

I₁ = A

4.Medium

A single-phase 50 kVA, 11000/400 V transformer operates at its rated load. Treat it as ideal. Find the current I_LV in the low-voltage winding.

S = 50 kVAV₁ = 11000 VV₂ = 400 V

I_LV = A

5.Hard

A single-phase 150 kVA transformer has a core loss of 600 W. At rated load and a power factor of 0.85 lagging its efficiency is 98.8%. Find the full-load copper loss P_cu,fl in watts.

S = 150 kVAP_core = 600 Wpf = 0.85η = 98.8%

P_cu,fl = W

6.Hard

A single-phase 25 kVA transformer has a core loss of 150 W and a copper loss of 450 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 25 kVAP_core = 150 WP_cu,fl = 450 W

S_η,max = kVA

Answer key

1. V₂ = 2400 V
2. N₂ = 50
3. I₁ = 1.438 A
4. I_LV = 125 A
5. P_cu,fl = 948.6 W
6. S_η,max = 14.43 kVA

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