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 60 turns on its primary winding and 240 turns on its secondary winding. The primary is connected to a 120 V AC supply. Find the secondary voltage V₂.

N₁ = 60N₂ = 240V₁ = 120 V

V₂ = V

2.Easy

An ideal transformer has 120 turns on its primary winding and 2400 turns on its secondary winding. The primary is connected to a 240 V AC supply. Find the secondary voltage V₂.

N₁ = 120N₂ = 2400V₁ = 240 V

V₂ = V

3.Medium

An amplifier with an output resistance of 64 Ω drives a 16 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 64 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 64 ΩR_L = 16 Ω

a =

4.Medium

A single-phase 75 kVA, 6600/230 V transformer operates at its rated load. Treat it as ideal. Find the current I_HV in the high-voltage winding.

S = 75 kVAV₁ = 6600 VV₂ = 230 V

I_HV = A

5.Hard

A single-phase 25 kVA transformer has a core loss of 100 W and a copper loss of 400 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 25 kVAP_core = 100 WP_cu,fl = 400 W

S_η,max = kVA

6.Hard

A single-phase 50 kVA transformer has a core loss of 200 W and a copper loss of 800 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 50 kVAP_core = 200 WP_cu,fl = 800 W

S_η,max = kVA

Answer key

1. V₂ = 480 V
2. V₂ = 4800 V
3. a = 2
4. I_HV = 11.36 A
5. S_η,max = 12.5 kVA
6. S_η,max = 25 kVA

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