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​ = 1250N2​ = 5010000 VV2​ = ?

An ideal transformer has 1250 turns on its primary winding and 50 turns on its secondary winding. The primary is connected to a 10000 V AC supply. Find the secondary voltage V2.

N1 = 1250N2 = 50V1 = 10000 V
V2 = V
2.Easy
N1​ = 1250N2​ = ?6000 V240 V

An ideal transformer must step 6000 V down to 240 V. Its primary winding has 1250 turns. How many turns N2 does the secondary winding need?

V1 = 6000 VV2 = 240 VN1 = 1250
N2 =
3.Medium
RL​ = 6 Ω21460 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 2:1 has 460 V applied to its primary winding. A 6 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 2:1V1 = 460 VRL = 6 Ω
I1 = A
4.Medium
2 ΩN1​N2​8 Ω

An amplifier with an output resistance of 8 Ω drives a 2 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 8 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

Rs = 8 ΩRL = 2 Ω
a =
5.Hard
pf 0.95250 kVA, η = 98.5%

A single-phase 250 kVA transformer has a core loss of 1250 W. At rated load and a power factor of 0.95 lagging its efficiency is 98.5%. Find the full-load copper loss Pcu,fl in watts.

S = 250 kVAPcore = 1250 Wpf = 0.95η = 98.5%
Pcu,fl = W
6.Hard
pf 0.9575 kVA, 25% load

A single-phase 75 kVA transformer has a core loss of 225 W and a copper loss of 675 W at rated load. It supplies 25% of its rated kVA at a power factor of 0.95 lagging. Find the total losses Ploss in watts at this load.

S = 75 kVAPcore = 225 WPcu,fl = 675 Wx = 0.25pf = 0.95
Ploss = W

Answer key

  1. 1. V2 = 400 V
  2. 2. N2 = 50
  3. 3. I1 = 19.17 A
  4. 4. a = 2
  5. 5. Pcu,fl = 2367 W
  6. 6. Ploss = 267.2 W

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