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​ = 60N2​ = 1200120 VV2​ = ?

An ideal transformer has 60 turns on its primary winding and 1200 turns on its secondary winding. The primary is connected to a 120 V AC supply. Find the secondary voltage V2.

N1 = 60N2 = 1200V1 = 120 V
V2 = V
2.Easy
N1​ = 80N2​ = 800120 VV2​ = ?

An ideal transformer has 80 turns on its primary winding and 800 turns on its secondary winding. The primary is connected to a 120 V AC supply. Find the secondary voltage V2.

N1 = 80N2 = 800V1 = 120 V
V2 = V
3.Medium
RL​ = 5 Ω41480 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 4:1 has 480 V applied to its primary winding. A 5 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 4:1V1 = 480 VRL = 5 Ω
I1 = A
4.Medium
10000 V400 VIHV​ILV​ = ?25 kVA

A single-phase 25 kVA, 10000/400 V transformer operates at its rated load. Treat it as ideal. Find the current ILV in the low-voltage winding.

S = 25 kVAV1 = 10000 VV2 = 400 V
ILV = A
5.Hard
pf 0.8525 kVA, 50% load

A single-phase 25 kVA transformer has a core loss of 200 W and a copper loss of 800 W at rated load. It supplies 50% of its rated kVA at a power factor of 0.85 lagging. Find the total losses Ploss in watts at this load.

S = 25 kVAPcore = 200 WPcu,fl = 800 Wx = 0.5pf = 0.85
Ploss = W
6.Hard
pf 0.850 kVA, 75% load

A single-phase 50 kVA transformer has a core loss of 250 W and a copper loss of 375 W at rated load. It supplies 75% of its rated kVA at a power factor of 0.8 lagging. Find the total losses Ploss in watts at this load.

S = 50 kVAPcore = 250 WPcu,fl = 375 Wx = 0.75pf = 0.8
Ploss = W

Answer key

  1. 1. V2 = 2400 V
  2. 2. V2 = 1200 V
  3. 3. I1 = 6 A
  4. 4. ILV = 62.5 A
  5. 5. Ploss = 400 W
  6. 6. Ploss = 460.9 W

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