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​ = 3200N2​ = 2003840 VV2​ = ?

An ideal transformer has 3200 turns on its primary winding and 200 turns on its secondary winding. The primary is connected to a 3840 V AC supply. Find the secondary voltage V2.

N1 = 3200N2 = 200V1 = 3840 V
V2 = V
2.Easy
N1​ = 600N2​ = ?1200 V120 V

An ideal transformer must step 1200 V down to 120 V. Its primary winding has 600 turns. How many turns N2 does the secondary winding need?

V1 = 1200 VV2 = 120 VN1 = 600
N2 =
3.Medium
4800 V240 VIHV​ILV​ = ?500 kVA

A single-phase 500 kVA, 4800/240 V transformer operates at its rated load. Treat it as ideal. Find the current ILV in the low-voltage winding.

S = 500 kVAV1 = 4800 VV2 = 240 V
ILV = A
4.Medium
RL​ = 10 Ω21460 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 2:1 has 460 V applied to its primary winding. A 10 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 2:1V1 = 460 VRL = 10 Ω
I1 = A
5.Hard
pf 0.95150 kVA, 50% load

A single-phase 150 kVA transformer has a core loss of 1200 W and a copper loss of 2400 W at rated load. It supplies 50% of its rated kVA at a power factor of 0.95 lagging. Find the total losses Ploss in watts at this load.

S = 150 kVAPcore = 1200 WPcu,fl = 2400 Wx = 0.5pf = 0.95
Ploss = W
6.Hard
pf 0.825 kVA, η = 98.2%

A single-phase 25 kVA transformer has a core loss of 200 W. At rated load and a power factor of 0.8 lagging its efficiency is 98.2%. Find the full-load copper loss Pcu,fl in watts.

S = 25 kVAPcore = 200 Wpf = 0.8η = 98.2%
Pcu,fl = W

Answer key

  1. 1. V2 = 240 V
  2. 2. N2 = 60
  3. 3. ILV = 2083 A
  4. 4. I1 = 11.5 A
  5. 5. Ploss = 1800 W
  6. 6. Pcu,fl = 166.6 W

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