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

An ideal transformer has 200 turns on its primary winding and 100 turns on its secondary winding. The primary is connected to a 240 V AC supply. Find the secondary voltage V₂.

N₁ = 200N₂ = 100V₁ = 240 V

V₂ = V

2.Easy

An ideal transformer has 800 turns on its primary winding and 80 turns on its secondary winding. The primary is connected to a 4000 V AC supply. Find the secondary voltage V₂.

N₁ = 800N₂ = 80V₁ = 4000 V

V₂ = V

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 2:1 has 460 V applied to its primary winding. An 8 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 2:1V₁ = 460 VR_L = 8 Ω

I₁ = A

4.Medium

A single-phase 250 kVA, 10000/400 V transformer operates at its rated load. Treat it as ideal. Find the current I_HV in the high-voltage winding.

S = 250 kVAV₁ = 10000 VV₂ = 400 V

I_HV = A

5.Hard

A single-phase 150 kVA transformer has a core loss of 900 W. At rated load and a power factor of 0.8 lagging its efficiency is 98.5%. Find the full-load copper loss P_cu,fl in watts.

S = 150 kVAP_core = 900 Wpf = 0.8η = 98.5%

P_cu,fl = W

6.Hard

A single-phase 100 kVA transformer has a core loss of 600 W and a copper loss of 2400 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 100 kVAP_core = 600 WP_cu,fl = 2400 W

S_η,max = kVA

Answer key

1. V₂ = 120 V
2. V₂ = 400 V
3. I₁ = 14.38 A
4. I_HV = 25 A
5. P_cu,fl = 927.4 W
6. S_η,max = 50 kVA

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