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 150 turns on its primary winding and 600 turns on its secondary winding. The primary is connected to a 110 V AC supply. Find the secondary voltage V₂.

N₁ = 150N₂ = 600V₁ = 110 V

V₂ = V

2.Easy

An ideal transformer has 500 turns on its primary winding and 50 turns on its secondary winding. The primary is connected to a 2400 V AC supply. Find the secondary voltage V₂.

N₁ = 500N₂ = 50V₁ = 2400 V

V₂ = V

3.Medium

A single-phase 75 kVA, 4160/480 V transformer operates at its rated load. Treat it as ideal. Find the current I_LV in the low-voltage winding.

S = 75 kVAV₁ = 4160 VV₂ = 480 V

I_LV = A

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 5:1 has 600 V applied to its primary winding. A 6 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 5:1V₁ = 600 VR_L = 6 Ω

I₁ = A

5.Hard

A single-phase 50 kVA transformer has a core loss of 250 W and a copper loss of 1000 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 50 kVAP_core = 250 WP_cu,fl = 1000 W

S_η,max = kVA

6.Hard

A single-phase 200 kVA transformer has a core loss of 1000 W and a copper loss of 4000 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 200 kVAP_core = 1000 WP_cu,fl = 4000 W

S_η,max = kVA

Answer key

1. V₂ = 440 V
2. V₂ = 240 V
3. I_LV = 156.3 A
4. I₁ = 4 A
5. S_η,max = 25 kVA
6. S_η,max = 100 kVA

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