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
N1​ = 150N2​ = 1500400 VV2​ = ?

An ideal transformer has 150 turns on its primary winding and 1500 turns on its secondary winding. The primary is connected to a 400 V AC supply. Find the secondary voltage V2.

N1 = 150N2 = 1500V1 = 400 V
V2 = V
2.Easy
N1​ = 7500N2​ = 15011500 VV2​ = ?

An ideal transformer has 7500 turns on its primary winding and 150 turns on its secondary winding. The primary is connected to an 11500 V AC supply. Find the secondary voltage V2.

N1 = 7500N2 = 150V1 = 11500 V
V2 = V
3.Medium
RL​ = 5 Ω41920 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 4:1 has 920 V applied to its primary winding. A 5 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 4:1V1 = 920 VRL = 5 Ω
I1 = A
4.Medium
RL​ = 10 Ω511150 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 5:1 has 1150 V applied to its primary winding. A 10 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 5:1V1 = 1150 VRL = 10 Ω
I1 = A
5.Hard
pf 0.9200 kVA, η = 97%

A single-phase 200 kVA transformer has a core loss of 1200 W. At rated load and a power factor of 0.9 lagging its efficiency is 97%. Find the full-load copper loss Pcu,fl in watts.

S = 200 kVAPcore = 1200 Wpf = 0.9η = 97%
Pcu,fl = W
6.Hard
pf 0.8550 kVA, η = 97%

A single-phase 50 kVA transformer has a core loss of 300 W. At rated load and a power factor of 0.85 lagging its efficiency is 97%. Find the full-load copper loss Pcu,fl in watts.

S = 50 kVAPcore = 300 Wpf = 0.85η = 97%
Pcu,fl = W

Answer key

  1. 1. V2 = 4000 V
  2. 2. V2 = 230 V
  3. 3. I1 = 11.5 A
  4. 4. I1 = 4.6 A
  5. 5. Pcu,fl = 4367 W
  6. 6. Pcu,fl = 1014 W

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