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 250 turns on its primary winding and 25 turns on its secondary winding. The primary is connected to a 2400 V AC supply. Find the secondary voltage V₂.

N₁ = 250N₂ = 25V₁ = 2400 V

V₂ = V

2.Easy

An ideal transformer has 80 turns on its primary winding and 320 turns on its secondary winding. The primary is connected to a 400 V AC supply. Find the secondary voltage V₂.

N₁ = 80N₂ = 320V₁ = 400 V

V₂ = V

3.Medium

A single-phase 100 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 = 100 kVAV₁ = 11000 VV₂ = 400 V

I_LV = A

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 2:1 has 480 V applied to its primary winding. A 30 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 2:1V₁ = 480 VR_L = 30 Ω

I₁ = A

5.Hard

A single-phase 75 kVA transformer has a core loss of 600 W. At rated load and a power factor of 0.85 lagging its efficiency is 96.5%. Find the full-load copper loss P_cu,fl in watts.

S = 75 kVAP_core = 600 Wpf = 0.85η = 96.5%

P_cu,fl = W

6.Hard

A single-phase 200 kVA transformer has a core loss of 1000 W and a copper loss of 3000 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 = 200 kVAP_core = 1000 WP_cu,fl = 3000 Wx = 0.5pf = 0.85

P_loss = W

Answer key

1. V₂ = 240 V
2. V₂ = 1600 V
3. I_LV = 250 A
4. I₁ = 4 A
5. P_cu,fl = 1712 W
6. P_loss = 1750 W

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