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 300 turns on its primary winding and 60 turns on its secondary winding. The primary is connected to a 1200 V AC supply. Find the secondary voltage V₂.

N₁ = 300N₂ = 60V₁ = 1200 V

V₂ = V

2.Easy

An ideal transformer has 250 turns on its primary winding and 6250 turns on its secondary winding. The primary is connected to a 240 V AC supply. Find the secondary voltage V₂.

N₁ = 250N₂ = 6250V₁ = 240 V

V₂ = V

3.Medium

A single-phase 150 kVA, 6600/230 V transformer operates at its rated load. Treat it as ideal. Find the current I_LV in the low-voltage winding.

S = 150 kVAV₁ = 6600 VV₂ = 230 V

I_LV = A

4.Medium

An amplifier with an output resistance of 1200 Ω drives a 75 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 1200 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 1200 ΩR_L = 75 Ω

a =

5.Hard

A single-phase 25 kVA transformer has a core loss of 125 W and a copper loss of 250 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 25 kVAP_core = 125 WP_cu,fl = 250 W

S_η,max = kVA

6.Hard

A single-phase 500 kVA transformer has a core loss of 4000 W and a copper loss of 16000 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 500 kVAP_core = 4000 WP_cu,fl = 16000 W

S_η,max = kVA

Answer key

1. V₂ = 240 V
2. V₂ = 6000 V
3. I_LV = 652.2 A
4. a = 4
5. S_η,max = 17.68 kVA
6. S_η,max = 250 kVA

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