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 1500 turns on its primary winding and 150 turns on its secondary winding. The primary is connected to a 4000 V AC supply. Find the secondary voltage V₂.

N₁ = 1500N₂ = 150V₁ = 4000 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 4000 V AC supply. Find the secondary voltage V₂.

N₁ = 1200N₂ = 120V₁ = 4000 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 48 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 20:1V₁ = 2400 VR_L = 48 Ω

I₁ = A

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 2:1 has 480 V applied to its primary winding. A 5 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 2:1V₁ = 480 VR_L = 5 Ω

I₁ = A

5.Hard

A single-phase 25 kVA transformer has a core loss of 75 W and a copper loss of 150 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 25 kVAP_core = 75 WP_cu,fl = 150 W

S_η,max = kVA

6.Hard

A single-phase 200 kVA transformer has a core loss of 1200 W and a copper loss of 1800 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 200 kVAP_core = 1200 WP_cu,fl = 1800 W

S_η,max = kVA

Answer key

1. V₂ = 400 V
2. V₂ = 400 V
3. I₁ = 0.125 A
4. I₁ = 24 A
5. S_η,max = 17.68 kVA
6. S_η,max = 163.3 kVA

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