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 5000 turns on its primary winding and 100 turns on its secondary winding. The primary is connected to a 20000 V AC supply. Find the secondary voltage V₂.

N₁ = 5000N₂ = 100V₁ = 20000 V

V₂ = V

2.Easy

An ideal transformer has 1200 turns on its primary winding and 120 turns on its secondary winding. The primary is connected to a 1200 V AC supply. Find the secondary voltage V₂.

N₁ = 1200N₂ = 120V₁ = 1200 V

V₂ = V

3.Medium

A single-phase 100 kVA, 480/240 V transformer operates at its rated load. Treat it as ideal. Find the current I_LV in the low-voltage winding.

S = 100 kVAV₁ = 480 VV₂ = 240 V

I_LV = A

4.Medium

A single-phase 25 kVA, 11000/400 V transformer operates at its rated load. Treat it as ideal. Find the current I_HV in the high-voltage winding.

S = 25 kVAV₁ = 11000 VV₂ = 400 V

I_HV = A

5.Hard

A single-phase 50 kVA transformer has a core loss of 250 W and a copper loss of 500 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 50 kVAP_core = 250 WP_cu,fl = 500 W

S_η,max = kVA

6.Hard

A single-phase 500 kVA transformer has a core loss of 4000 W and a copper loss of 12000 W at rated load. It supplies 50% of its rated kVA at a power factor of 0.85 lagging. Find the total losses P_loss in watts at this load.

S = 500 kVAP_core = 4000 WP_cu,fl = 12000 Wx = 0.5pf = 0.85

P_loss = W

Answer key

1. V₂ = 400 V
2. V₂ = 120 V
3. I_LV = 416.7 A
4. I_HV = 2.273 A
5. S_η,max = 35.36 kVA
6. P_loss = 7000 W

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