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 4000 turns on its primary winding and 80 turns on its secondary winding. The primary is connected to an 11500 V AC supply. Find the secondary voltage V₂.

N₁ = 4000N₂ = 80V₁ = 11500 V

V₂ = V

2.Easy

An ideal transformer has 600 turns on its primary winding and 150 turns on its secondary winding. The primary is connected to a 480 V AC supply. Find the secondary voltage V₂.

N₁ = 600N₂ = 150V₁ = 480 V

V₂ = V

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 20:1 has 4600 V applied to its primary winding. A 10 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 20:1V₁ = 4600 VR_L = 10 Ω

I₁ = A

4.Medium

An amplifier with an output resistance of 1600 Ω drives a 16 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 1600 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 1600 ΩR_L = 16 Ω

a =

5.Hard

A single-phase 250 kVA transformer has a core loss of 1250 W and a copper loss of 3750 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 250 kVAP_core = 1250 WP_cu,fl = 3750 W

S_η,max = kVA

6.Hard

A single-phase 150 kVA transformer has a core loss of 600 W. At rated load and a power factor of 0.85 lagging its efficiency is 99%. Find the full-load copper loss P_cu,fl in watts.

S = 150 kVAP_core = 600 Wpf = 0.85η = 99%

P_cu,fl = W

Answer key

1. V₂ = 230 V
2. V₂ = 120 V
3. I₁ = 1.15 A
4. a = 10
5. S_η,max = 144.3 kVA
6. P_cu,fl = 687.9 W

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