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​ = 200N2​ = 251920 VV2​ = ?

An ideal transformer has 200 turns on its primary winding and 25 turns on its secondary winding. The primary is connected to a 1920 V AC supply. Find the secondary voltage V2.

N1 = 200N2 = 25V1 = 1920 V
V2 = V
2.Easy
N1​ = 320N2​ = 80920 VV2​ = ?

An ideal transformer has 320 turns on its primary winding and 80 turns on its secondary winding. The primary is connected to a 920 V AC supply. Find the secondary voltage V2.

N1 = 320N2 = 80V1 = 920 V
V2 = V
3.Medium
4800 V240 VIHV​ILV​ = ?100 kVA

A single-phase 100 kVA, 4800/240 V transformer operates at its rated load. Treat it as ideal. Find the current ILV in the low-voltage winding.

S = 100 kVAV1 = 4800 VV2 = 240 V
ILV = A
4.Medium
5 Ω51

A 5 Ω resistor is connected across the secondary winding of an ideal transformer with a turns ratio N₁:N₂ = 5:1. Find the resistance R1′ seen looking into the primary winding.

N1:N2 = 5:1RL = 5 Ω
R1′ = Ω
5.Hard
pf 0.850 kVA, 75% load

A single-phase 50 kVA transformer has a core loss of 200 W and a copper loss of 300 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 = 200 WPcu,fl = 300 Wx = 0.75pf = 0.8
Ploss = W
6.Hard
pf 0.85500 kVA, 75% load

A single-phase 500 kVA transformer has a core loss of 4000 W and a copper loss of 10000 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 = 500 kVAPcore = 4000 WPcu,fl = 10000 Wx = 0.75pf = 0.85
Ploss = W

Answer key

  1. 1. V2 = 240 V
  2. 2. V2 = 230 V
  3. 3. ILV = 416.7 A
  4. 4. R1′ = 125 Ω
  5. 5. Ploss = 368.8 W
  6. 6. Ploss = 9625 W

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