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 1250 turns on its primary winding and 50 turns on its secondary winding. The primary is connected to a 5750 V AC supply. Find the secondary voltage V₂.

N₁ = 1250N₂ = 50V₁ = 5750 V

V₂ = V

2.Easy

An ideal transformer has 1280 turns on its primary winding and 80 turns on its secondary winding. The primary is connected to a 1920 V AC supply. Find the secondary voltage V₂.

N₁ = 1280N₂ = 80V₁ = 1920 V

V₂ = V

3.Medium

An amplifier with an output resistance of 576 Ω drives a 4 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 576 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 576 ΩR_L = 4 Ω

a =

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 10:1 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 = 10:1V₁ = 1200 VR_L = 48 Ω

I₁ = A

5.Hard

A single-phase 75 kVA transformer has a core loss of 450 W. At rated load and a power factor of 0.9 lagging its efficiency is 98%. Find the full-load copper loss P_cu,fl in watts.

S = 75 kVAP_core = 450 Wpf = 0.9η = 98%

P_cu,fl = W

6.Hard

A single-phase 250 kVA transformer has a core loss of 1250 W and a copper loss of 5000 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 250 kVAP_core = 1250 WP_cu,fl = 5000 W

S_η,max = kVA

Answer key

1. V₂ = 230 V
2. V₂ = 120 V
3. a = 12
4. I₁ = 0.25 A
5. P_cu,fl = 927.6 W
6. S_η,max = 125 kVA

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