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​ = 2000N2​ = 509200 VV2​ = ?

An ideal transformer has 2000 turns on its primary winding and 50 turns on its secondary winding. The primary is connected to a 9200 V AC supply. Find the secondary voltage V2.

N1 = 2000N2 = 50V1 = 9200 V
V2 = V
2.Easy
N1​ = 6000N2​ = 1509600 VV2​ = ?

An ideal transformer has 6000 turns on its primary winding and 150 turns on its secondary winding. The primary is connected to a 9600 V AC supply. Find the secondary voltage V2.

N1 = 6000N2 = 150V1 = 9600 V
V2 = V
3.Medium
RL​ = 10 Ω51600 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 5:1 has 600 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 = 600 VRL = 10 Ω
I1 = A
4.Medium
RL​ = 30 Ω2014600 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 20:1 has 4600 V applied to its primary winding. A 30 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 20:1V1 = 4600 VRL = 30 Ω
I1 = A
5.Hard
pf 0.85250 kVA, 75% load

A single-phase 250 kVA transformer has a core loss of 750 W and a copper loss of 1125 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 = 250 kVAPcore = 750 WPcu,fl = 1125 Wx = 0.75pf = 0.85
Ploss = W
6.Hard
pf 0.85500 kVA, η = 97.5%

A single-phase 500 kVA transformer has a core loss of 1500 W. At rated load and a power factor of 0.85 lagging its efficiency is 97.5%. Find the full-load copper loss Pcu,fl in watts.

S = 500 kVAPcore = 1500 Wpf = 0.85η = 97.5%
Pcu,fl = W

Answer key

  1. 1. V2 = 230 V
  2. 2. V2 = 240 V
  3. 3. I1 = 2.4 A
  4. 4. I1 = 0.3833 A
  5. 5. Ploss = 1383 W
  6. 6. Pcu,fl = 9397 W

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