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​ = 500N2​ = ?8000 V400 V

An ideal transformer must step 8000 V down to 400 V. Its primary winding has 500 turns. How many turns N2 does the secondary winding need?

V1 = 8000 VV2 = 400 VN1 = 500
N2 =
2.Easy
N1​ = 7500N2​ = ?6000 V120 V

An ideal transformer must step 6000 V down to 120 V. Its primary winding has 7500 turns. How many turns N2 does the secondary winding need?

V1 = 6000 VV2 = 120 VN1 = 7500
N2 =
3.Medium
RL​ = 12 Ω1012400 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 10:1 has 2400 V applied to its primary winding. A 12 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 10:1V1 = 2400 VRL = 12 Ω
I1 = A
4.Medium
6600 V230 VIHV​ = ?ILV​500 kVA

A single-phase 500 kVA, 6600/230 V transformer operates at its rated load. Treat it as ideal. Find the current IHV in the high-voltage winding.

S = 500 kVAV1 = 6600 VV2 = 230 V
IHV = A
5.Hard
pf 0.8575 kVA, 50% load

A single-phase 75 kVA transformer has a core loss of 600 W and a copper loss of 2400 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 = 75 kVAPcore = 600 WPcu,fl = 2400 Wx = 0.5pf = 0.85
Ploss = W
6.Hard
pf 0.95150 kVA, 25% load

A single-phase 150 kVA transformer has a core loss of 450 W and a copper loss of 1350 W at rated load. It supplies 25% 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 = 450 WPcu,fl = 1350 Wx = 0.25pf = 0.95
Ploss = W

Answer key

  1. 1. N2 = 25
  2. 2. N2 = 150
  3. 3. I1 = 2 A
  4. 4. IHV = 75.76 A
  5. 5. Ploss = 1200 W
  6. 6. Ploss = 534.4 W

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