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​ = 400N2​ = 402400 VV2​ = ?

An ideal transformer has 400 turns on its primary winding and 40 turns on its secondary winding. The primary is connected to a 2400 V AC supply. Find the secondary voltage V2.

N1 = 400N2 = 40V1 = 2400 V
V2 = V
2.Easy
N1​ = 1000N2​ = 406000 VV2​ = ?

An ideal transformer has 1000 turns on its primary winding and 40 turns on its secondary winding. The primary is connected to a 6000 V AC supply. Find the secondary voltage V2.

N1 = 1000N2 = 40V1 = 6000 V
V2 = V
3.Medium
4 ΩN1​N2​100 Ω

An amplifier with an output resistance of 100 Ω drives a 4 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 100 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

Rs = 100 ΩRL = 4 Ω
a =
4.Medium
RL​ = 40 Ω21460 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 2:1 has 460 V applied to its primary winding. A 40 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 2:1V1 = 460 VRL = 40 Ω
I1 = A
5.Hard
pf 0.8500 kVA, 50% load

A single-phase 500 kVA transformer has a core loss of 2000 W and a copper loss of 4000 W at rated load. It supplies 50% of its rated kVA at a power factor of 0.8 lagging. Find the total losses Ploss in watts at this load.

S = 500 kVAPcore = 2000 WPcu,fl = 4000 Wx = 0.5pf = 0.8
Ploss = W
6.Hard
pf 0.8250 kVA, η = 98.5%

A single-phase 250 kVA transformer has a core loss of 750 W. At rated load and a power factor of 0.8 lagging its efficiency is 98.5%. Find the full-load copper loss Pcu,fl in watts.

S = 250 kVAPcore = 750 Wpf = 0.8η = 98.5%
Pcu,fl = W

Answer key

  1. 1. V2 = 240 V
  2. 2. V2 = 240 V
  3. 3. a = 5
  4. 4. I1 = 2.875 A
  5. 5. Ploss = 3000 W
  6. 6. Pcu,fl = 2296 W

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