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​ = 800N2​ = ?960 V120 V

An ideal transformer must step 960 V down to 120 V. Its primary winding has 800 turns. How many turns N2 does the secondary winding need?

V1 = 960 VV2 = 120 VN1 = 800
N2 =
2.Easy
N1​ = 80N2​ = ?480 V240 V

An ideal transformer must step 480 V down to 240 V. Its primary winding has 80 turns. How many turns N2 does the secondary winding need?

V1 = 480 VV2 = 240 VN1 = 80
N2 =
3.Medium
6600 V230 VIHV​ = ?ILV​25 kVA

A single-phase 25 kVA, 6600/230 V transformer operates at its rated load. Treat it as ideal. Find the current IHV in the high-voltage winding.

S = 25 kVAV1 = 6600 VV2 = 230 V
IHV = A
4.Medium
480 V240 VIHV​ILV​ = ?250 kVA

A single-phase 250 kVA, 480/240 V transformer operates at its rated load. Treat it as ideal. Find the current ILV in the low-voltage winding.

S = 250 kVAV1 = 480 VV2 = 240 V
ILV = A
5.Hard
pf 0.8150 kVA, 50% load

A single-phase 150 kVA transformer has a core loss of 1200 W and a copper loss of 1800 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 = 150 kVAPcore = 1200 WPcu,fl = 1800 Wx = 0.5pf = 0.8
Ploss = W
6.Hard
pf 0.9250 kVA, 50% load

A single-phase 250 kVA transformer has a core loss of 1250 W and a copper loss of 5000 W at rated load. It supplies 50% of its rated kVA at a power factor of 0.9 lagging. Find the total losses Ploss in watts at this load.

S = 250 kVAPcore = 1250 WPcu,fl = 5000 Wx = 0.5pf = 0.9
Ploss = W

Answer key

  1. 1. N2 = 100
  2. 2. N2 = 40
  3. 3. IHV = 3.788 A
  4. 4. ILV = 1042 A
  5. 5. Ploss = 1650 W
  6. 6. Ploss = 2500 W

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