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 200 turns on its primary winding and 1000 turns on its secondary winding. The primary is connected to a 230 V AC supply. Find the secondary voltage V₂.

N₁ = 200N₂ = 1000V₁ = 230 V

V₂ = V

2.Easy

An ideal transformer has 320 turns on its primary winding and 40 turns on its secondary winding. The primary is connected to a 1920 V AC supply. Find the secondary voltage V₂.

N₁ = 320N₂ = 40V₁ = 1920 V

V₂ = V

3.Medium

An amplifier with an output resistance of 1250 Ω drives a 50 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 1250 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 1250 ΩR_L = 50 Ω

a =

4.Medium

An amplifier with an output resistance of 512 Ω drives an 8 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 512 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 512 ΩR_L = 8 Ω

a =

5.Hard

A single-phase 150 kVA transformer has a core loss of 900 W and a copper loss of 2250 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 150 kVAP_core = 900 WP_cu,fl = 2250 W

S_η,max = kVA

6.Hard

A single-phase 500 kVA transformer has a core loss of 2000 W. At rated load and a power factor of 0.8 lagging its efficiency is 98.2%. Find the full-load copper loss P_cu,fl in watts.

S = 500 kVAP_core = 2000 Wpf = 0.8η = 98.2%

P_cu,fl = W

Answer key

1. V₂ = 1150 V
2. V₂ = 240 V
3. a = 5
4. a = 8
5. S_η,max = 94.87 kVA
6. P_cu,fl = 5332 W

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