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 1600 turns on its primary winding and 80 turns on its secondary winding. The primary is connected to a 4600 V AC supply. Find the secondary voltage V₂.

N₁ = 1600N₂ = 80V₁ = 4600 V

V₂ = V

2.Easy

An ideal transformer has 50 turns on its primary winding and 400 turns on its secondary winding. The primary is connected to a 690 V AC supply. Find the secondary voltage V₂.

N₁ = 50N₂ = 400V₁ = 690 V

V₂ = V

3.Medium

A single-phase 150 kVA, 7200/240 V transformer operates at its rated load. Treat it as ideal. Find the current I_HV in the high-voltage winding.

S = 150 kVAV₁ = 7200 VV₂ = 240 V

I_HV = A

4.Medium

An amplifier with an output resistance of 128 Ω drives an 8 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 128 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 128 ΩR_L = 8 Ω

a =

5.Hard

A single-phase 250 kVA transformer has a core loss of 750 W and a copper loss of 2250 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 250 kVAP_core = 750 WP_cu,fl = 2250 W

S_η,max = kVA

6.Hard

A single-phase 75 kVA transformer has a core loss of 375 W and a copper loss of 562.5 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 75 kVAP_core = 375 WP_cu,fl = 562.5 W

S_η,max = kVA

Answer key

1. V₂ = 230 V
2. V₂ = 5520 V
3. I_HV = 20.83 A
4. a = 4
5. S_η,max = 144.3 kVA
6. S_η,max = 61.24 kVA

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