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 100 turns on its primary winding and 2000 turns on its secondary winding. The primary is connected to a 240 V AC supply. Find the secondary voltage V₂.

N₁ = 100N₂ = 2000V₁ = 240 V

V₂ = V

2.Easy

An ideal transformer has 60 turns on its primary winding and 480 turns on its secondary winding. The primary is connected to a 110 V AC supply. Find the secondary voltage V₂.

N₁ = 60N₂ = 480V₁ = 110 V

V₂ = V

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 20:1 has 4600 V applied to its primary winding. A 30 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 20:1V₁ = 4600 VR_L = 30 Ω

I₁ = A

4.Medium

A single-phase 50 kVA, 7200/240 V transformer operates at its rated load. Treat it as ideal. Find the current I_LV in the low-voltage winding.

S = 50 kVAV₁ = 7200 VV₂ = 240 V

I_LV = A

5.Hard

A single-phase 100 kVA transformer has a core loss of 300 W and a copper loss of 450 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 100 kVAP_core = 300 WP_cu,fl = 450 W

S_η,max = kVA

6.Hard

A single-phase 25 kVA transformer has a core loss of 100 W. At rated load and a power factor of 0.9 lagging its efficiency is 96.5%. Find the full-load copper loss P_cu,fl in watts.

S = 25 kVAP_core = 100 Wpf = 0.9η = 96.5%

P_cu,fl = W

Answer key

1. V₂ = 4800 V
2. V₂ = 880 V
3. I₁ = 0.3833 A
4. I_LV = 208.3 A
5. S_η,max = 81.65 kVA
6. P_cu,fl = 716.1 W

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