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​ = 50N2​ = 500230 VV2​ = ?

An ideal transformer has 50 turns on its primary winding and 500 turns on its secondary winding. The primary is connected to a 230 V AC supply. Find the secondary voltage V2.

N1 = 50N2 = 500V1 = 230 V
V2 = V
2.Easy
N1​ = 150N2​ = 750400 VV2​ = ?

An ideal transformer has 150 turns on its primary winding and 750 turns on its secondary winding. The primary is connected to a 400 V AC supply. Find the secondary voltage V2.

N1 = 150N2 = 750V1 = 400 V
V2 = V
3.Medium
RL​ = 20 Ω41960 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 4:1 has 960 V applied to its primary winding. A 20 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 4:1V1 = 960 VRL = 20 Ω
I1 = A
4.Medium
RL​ = 8 Ω1012300 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 10:1 has 2300 V applied to its primary winding. An 8 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 10:1V1 = 2300 VRL = 8 Ω
I1 = A
5.Hard
pf 0.85200 kVA, 75% load

A single-phase 200 kVA transformer has a core loss of 1200 W and a copper loss of 3600 W at rated load. It supplies 75% of its rated kVA at a power factor of 0.85 lagging. Find the total losses Ploss in watts at this load.

S = 200 kVAPcore = 1200 WPcu,fl = 3600 Wx = 0.75pf = 0.85
Ploss = W
6.Hard
pf 0.95500 kVA, η = 98.8%

A single-phase 500 kVA transformer has a core loss of 1500 W. At rated load and a power factor of 0.95 lagging its efficiency is 98.8%. Find the full-load copper loss Pcu,fl in watts.

S = 500 kVAPcore = 1500 Wpf = 0.95η = 98.8%
Pcu,fl = W

Answer key

  1. 1. V2 = 2300 V
  2. 2. V2 = 2000 V
  3. 3. I1 = 3 A
  4. 4. I1 = 2.875 A
  5. 5. Ploss = 3225 W
  6. 6. Pcu,fl = 4269 W

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