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 must step 4600 V down to 230 V. Its primary winding has 3000 turns. How many turns N₂ does the secondary winding need?

V₁ = 4600 VV₂ = 230 VN₁ = 3000

N₂ =

2.Easy

An ideal transformer has 2000 turns on its primary winding and 200 turns on its secondary winding. The primary is connected to a 2400 V AC supply. Find the secondary voltage V₂.

N₁ = 2000N₂ = 200V₁ = 2400 V

V₂ = V

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 5:1 has 600 V applied to its primary winding. A 15 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 5:1V₁ = 600 VR_L = 15 Ω

I₁ = A

4.Medium

A single-phase 10 kVA, 10000/400 V transformer operates at its rated load. Treat it as ideal. Find the current I_LV in the low-voltage winding.

S = 10 kVAV₁ = 10000 VV₂ = 400 V

I_LV = A

5.Hard

A single-phase 200 kVA transformer has a core loss of 600 W and a copper loss of 1500 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 200 kVAP_core = 600 WP_cu,fl = 1500 W

S_η,max = kVA

6.Hard

A single-phase 150 kVA transformer has a core loss of 1200 W. At rated load and a power factor of 0.95 lagging its efficiency is 97%. Find the full-load copper loss P_cu,fl in watts.

S = 150 kVAP_core = 1200 Wpf = 0.95η = 97%

P_cu,fl = W

Answer key

1. N₂ = 150
2. V₂ = 240 V
3. I₁ = 1.6 A
4. I_LV = 25 A
5. S_η,max = 126.5 kVA
6. P_cu,fl = 3207 W

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