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​ = 80N2​ = 800230 VV2​ = ?

An ideal transformer has 80 turns on its primary winding and 800 turns on its secondary winding. The primary is connected to a 230 V AC supply. Find the secondary voltage V2.

N1 = 80N2 = 800V1 = 230 V
V2 = V
2.Easy
N1​ = 3200N2​ = ?9200 V230 V

An ideal transformer must step 9200 V down to 230 V. Its primary winding has 3200 turns. How many turns N2 does the secondary winding need?

V1 = 9200 VV2 = 230 VN1 = 3200
N2 =
3.Medium
11000 V400 VIHV​ = ?ILV​250 kVA

A single-phase 250 kVA, 11000/400 V transformer operates at its rated load. Treat it as ideal. Find the current IHV in the high-voltage winding.

S = 250 kVAV1 = 11000 VV2 = 400 V
IHV = A
4.Medium
480 V240 VIHV​ = ?ILV​10 kVA

A single-phase 10 kVA, 480/240 V transformer operates at its rated load. Treat it as ideal. Find the current IHV in the high-voltage winding.

S = 10 kVAV1 = 480 VV2 = 240 V
IHV = A
5.Hard
150 kVA

A single-phase 150 kVA transformer has a core loss of 600 W and a copper loss of 1500 W at rated load. At what load Sη,max, in kVA, is its efficiency highest?

S = 150 kVAPcore = 600 WPcu,fl = 1500 W
Sη,max = kVA
6.Hard
100 kVA

A single-phase 100 kVA transformer has a core loss of 800 W and a copper loss of 2000 W at rated load. At what load Sη,max, in kVA, is its efficiency highest?

S = 100 kVAPcore = 800 WPcu,fl = 2000 W
Sη,max = kVA

Answer key

  1. 1. V2 = 2300 V
  2. 2. N2 = 80
  3. 3. IHV = 22.73 A
  4. 4. IHV = 20.83 A
  5. 5. Sη,max = 94.87 kVA
  6. 6. Sη,max = 63.25 kVA

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