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 must step 2400 V down to 240 V. Its primary winding has 500 turns. How many turns N₂ does the secondary winding need?

V₁ = 2400 VV₂ = 240 VN₁ = 500

N₂ =

2.Easy

An ideal transformer has 200 turns on its primary winding and 5000 turns on its secondary winding. The primary is connected to a 230 V AC supply. Find the secondary voltage V₂.

N₁ = 200N₂ = 5000V₁ = 230 V

V₂ = V

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 10:1 has 2300 V applied to its primary winding. A 48 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 10:1V₁ = 2300 VR_L = 48 Ω

I₁ = A

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 10:1 has 2300 V applied to its primary winding. A 12 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 10:1V₁ = 2300 VR_L = 12 Ω

I₁ = A

5.Hard

A single-phase 500 kVA transformer has a core loss of 4000 W and a copper loss of 10000 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 500 kVAP_core = 4000 WP_cu,fl = 10000 W

S_η,max = kVA

6.Hard

A single-phase 150 kVA transformer has a core loss of 750 W and a copper loss of 1875 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 150 kVAP_core = 750 WP_cu,fl = 1875 W

S_η,max = kVA

Answer key

1. N₂ = 50
2. V₂ = 5750 V
3. I₁ = 0.4792 A
4. I₁ = 1.917 A
5. S_η,max = 316.2 kVA
6. S_η,max = 94.87 kVA

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