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​ = 200400 VV2​ = ?

An ideal transformer has 50 turns on its primary winding and 200 turns on its secondary winding. The primary is connected to a 400 V AC supply. Find the secondary voltage V2.

N1 = 50N2 = 200V1 = 400 V
V2 = V
2.Easy
N1​ = 3000N2​ = ?12000 V240 V

An ideal transformer must step 12000 V down to 240 V. Its primary winding has 3000 turns. How many turns N2 does the secondary winding need?

V1 = 12000 VV2 = 240 VN1 = 3000
N2 =
3.Medium
4160 V480 VIHV​ = ?ILV​250 kVA

A single-phase 250 kVA, 4160/480 V transformer operates at its rated load. Treat it as ideal. Find the current IHV in the high-voltage winding.

S = 250 kVAV1 = 4160 VV2 = 480 V
IHV = A
4.Medium
RL​ = 15 Ω41480 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 4:1 has 480 V applied to its primary winding. A 15 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 4:1V1 = 480 VRL = 15 Ω
I1 = A
5.Hard
pf 0.875 kVA, η = 98%

A single-phase 75 kVA transformer has a core loss of 375 W. At rated load and a power factor of 0.8 lagging its efficiency is 98%. Find the full-load copper loss Pcu,fl in watts.

S = 75 kVAPcore = 375 Wpf = 0.8η = 98%
Pcu,fl = W
6.Hard
pf 0.85500 kVA, η = 96%

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 96%. Find the full-load copper loss Pcu,fl in watts.

S = 500 kVAPcore = 1500 Wpf = 0.85η = 96%
Pcu,fl = W

Answer key

  1. 1. V2 = 1600 V
  2. 2. N2 = 60
  3. 3. IHV = 60.1 A
  4. 4. I1 = 2 A
  5. 5. Pcu,fl = 849.5 W
  6. 6. Pcu,fl = 16208 W

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