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​ = 80N2​ = 2000230 VV2​ = ?

An ideal transformer has 80 turns on its primary winding and 2000 turns on its secondary winding. The primary is connected to a 230 V AC supply. Find the secondary voltage V2.

N1 = 80N2 = 2000V1 = 230 V
V2 = V
2.Easy
N1​ = 1000N2​ = ?5750 V230 V

An ideal transformer must step 5750 V down to 230 V. Its primary winding has 1000 turns. How many turns N2 does the secondary winding need?

V1 = 5750 VV2 = 230 VN1 = 1000
N2 =
3.Medium
RL​ = 48 Ω511200 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 5:1 has 1200 V applied to its primary winding. A 48 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 5:1V1 = 1200 VRL = 48 Ω
I1 = A
4.Medium
RL​ = 8 Ω21480 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 2:1 has 480 V applied to its primary winding. An 8 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 2:1V1 = 480 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 4800 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 = 4800 Wx = 0.75pf = 0.85
Ploss = W
6.Hard
pf 0.9200 kVA, η = 98.8%

A single-phase 200 kVA transformer has a core loss of 1000 W. At rated load and a power factor of 0.9 lagging its efficiency is 98.8%. Find the full-load copper loss Pcu,fl in watts.

S = 200 kVAPcore = 1000 Wpf = 0.9η = 98.8%
Pcu,fl = W

Answer key

  1. 1. V2 = 5750 V
  2. 2. N2 = 40
  3. 3. I1 = 1 A
  4. 4. I1 = 15 A
  5. 5. Ploss = 3900 W
  6. 6. Pcu,fl = 1186 W

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