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 must step 480 V down to 120 V. Its primary winding has 200 turns. How many turns N₂ does the secondary winding need?

V₁ = 480 VV₂ = 120 VN₁ = 200

N₂ =

2.Easy

An ideal transformer has 120 turns on its primary winding and 3000 turns on its secondary winding. The primary is connected to a 230 V AC supply. Find the secondary voltage V₂.

N₁ = 120N₂ = 3000V₁ = 230 V

V₂ = V

3.Medium

A 16 Ω resistor is connected across the secondary winding of an ideal transformer with a turns ratio N₁:N₂ = 2:1. Find the resistance R_1′ seen looking into the primary winding.

N₁:N₂ = 2:1R_L = 16 Ω

R_1′ = Ω

4.Medium

A single-phase 75 kVA, 6600/230 V transformer operates at its rated load. Treat it as ideal. Find the current I_LV in the low-voltage winding.

S = 75 kVAV₁ = 6600 VV₂ = 230 V

I_LV = A

5.Hard

A single-phase 100 kVA transformer has a core loss of 800 W and a copper loss of 3200 W at rated load. It supplies 75% of its rated kVA at a power factor of 0.8 lagging. Find the total losses P_loss in watts at this load.

S = 100 kVAP_core = 800 WP_cu,fl = 3200 Wx = 0.75pf = 0.8

P_loss = W

6.Hard

A single-phase 75 kVA transformer has a core loss of 450 W and a copper loss of 1125 W at rated load. It supplies 50% of its rated kVA at a power factor of 0.9 lagging. Find the total losses P_loss in watts at this load.

S = 75 kVAP_core = 450 WP_cu,fl = 1125 Wx = 0.5pf = 0.9

P_loss = W

Answer key

1. N₂ = 50
2. V₂ = 5750 V
3. R_1′ = 64 Ω
4. I_LV = 326.1 A
5. P_loss = 2600 W
6. P_loss = 731.3 W

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