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.

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1.Easy

An ideal transformer has 160 turns on its primary winding and 80 turns on its secondary winding. The primary is connected to a 480 V AC supply. Find the secondary voltage V₂.

N₁ = 160N₂ = 80V₁ = 480 V

V₂ = V

2.Easy

An ideal transformer has 800 turns on its primary winding and 100 turns on its secondary winding. The primary is connected to a 1920 V AC supply. Find the secondary voltage V₂.

N₁ = 800N₂ = 100V₁ = 1920 V

V₂ = V

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 20:1 has 2400 V applied to its primary winding. A 4 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 20:1V₁ = 2400 VR_L = 4 Ω

I₁ = A

4.Medium

A single-phase 10 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 = 10 kVAV₁ = 480 VV₂ = 240 V

I_LV = 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 75 kVA transformer has a core loss of 600 W and a copper loss of 1800 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 75 kVAP_core = 600 WP_cu,fl = 1800 W

S_η,max = kVA

Answer key

1. V₂ = 240 V
2. V₂ = 240 V
3. I₁ = 1.5 A
4. I_LV = 41.67 A
5. S_η,max = 35.36 kVA
6. S_η,max = 43.3 kVA

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