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 460 V down to 230 V. Its primary winding has 300 turns. How many turns N₂ does the secondary winding need?

V₁ = 460 VV₂ = 230 VN₁ = 300

N₂ =

2.Easy

An ideal transformer has 1600 turns on its primary winding and 40 turns on its secondary winding. The primary is connected to a 9600 V AC supply. Find the secondary voltage V₂.

N₁ = 1600N₂ = 40V₁ = 9600 V

V₂ = V

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 10:1 has 1200 V applied to its primary winding. A 4 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 10:1V₁ = 1200 VR_L = 4 Ω

I₁ = 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 250 kVA transformer has a core loss of 2000 W. At rated load and a power factor of 0.95 lagging its efficiency is 98.2%. Find the full-load copper loss P_cu,fl in watts.

S = 250 kVAP_core = 2000 Wpf = 0.95η = 98.2%

P_cu,fl = W

6.Hard

A single-phase 25 kVA transformer has a core loss of 100 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 = 25 kVAP_core = 100 Wpf = 0.9η = 98%

P_cu,fl = W

Answer key

1. N₂ = 150
2. V₂ = 240 V
3. I₁ = 3 A
4. a = 8
5. P_cu,fl = 2353 W
6. P_cu,fl = 359.2 W

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