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 120 turns on its primary winding and 6000 turns on its secondary winding. The primary is connected to a 240 V AC supply. Find the secondary voltage V₂.

N₁ = 120N₂ = 6000V₁ = 240 V

V₂ = V

2.Easy

An ideal transformer must step 10000 V down to 400 V. Its primary winding has 1250 turns. How many turns N₂ does the secondary winding need?

V₁ = 10000 VV₂ = 400 VN₁ = 1250

N₂ =

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 5:1 has 1200 V applied to its primary winding. A 48 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 5:1V₁ = 1200 VR_L = 48 Ω

I₁ = A

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 5:1 has 1200 V applied to its primary winding. A 12 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 5:1V₁ = 1200 VR_L = 12 Ω

I₁ = A

5.Hard

A single-phase 500 kVA transformer has a core loss of 2000 W. At rated load and a power factor of 0.85 lagging its efficiency is 96%. Find the full-load copper loss P_cu,fl in watts.

S = 500 kVAP_core = 2000 Wpf = 0.85η = 96%

P_cu,fl = W

6.Hard

A single-phase 100 kVA transformer has a core loss of 400 W and a copper loss of 1600 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 100 kVAP_core = 400 WP_cu,fl = 1600 W

S_η,max = kVA

Answer key

1. V₂ = 12000 V
2. N₂ = 50
3. I₁ = 1 A
4. I₁ = 4 A
5. P_cu,fl = 15708 W
6. S_η,max = 50 kVA

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