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 150 turns on its primary winding and 1500 turns on its secondary winding. The primary is connected to a 110 V AC supply. Find the secondary voltage V₂.

N₁ = 150N₂ = 1500V₁ = 110 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 230 V AC supply. Find the secondary voltage V₂.

N₁ = 60N₂ = 480V₁ = 230 V

V₂ = V

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 20:1 has 4800 V applied to its primary winding. A 20 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 20:1V₁ = 4800 VR_L = 20 Ω

I₁ = A

4.Medium

A single-phase 10 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 = 10 kVAV₁ = 7200 VV₂ = 240 V

I_LV = A

5.Hard

A single-phase 100 kVA transformer has a core loss of 500 W and a copper loss of 750 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 100 kVAP_core = 500 WP_cu,fl = 750 W

S_η,max = kVA

6.Hard

A single-phase 50 kVA transformer has a core loss of 400 W and a copper loss of 800 W at rated load. It supplies 50% of its rated kVA at a power factor of 0.85 lagging. Find the total losses P_loss in watts at this load.

S = 50 kVAP_core = 400 WP_cu,fl = 800 Wx = 0.5pf = 0.85

P_loss = W

Answer key

1. V₂ = 1100 V
2. V₂ = 1840 V
3. I₁ = 0.6 A
4. I_LV = 41.67 A
5. S_η,max = 81.65 kVA
6. P_loss = 600 W

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