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 800 turns on its primary winding and 100 turns on its secondary winding. The primary is connected to a 1920 V AC supply. Find the secondary voltage V₂.

N₁ = 800N₂ = 100V₁ = 1920 V

V₂ = V

2.Easy

An ideal transformer has 100 turns on its primary winding and 200 turns on its secondary winding. The primary is connected to a 120 V AC supply. Find the secondary voltage V₂.

N₁ = 100N₂ = 200V₁ = 120 V

V₂ = V

3.Medium

A single-phase 500 kVA, 11000/400 V transformer operates at its rated load. Treat it as ideal. Find the current I_HV in the high-voltage winding.

S = 500 kVAV₁ = 11000 VV₂ = 400 V

I_HV = A

4.Medium

A single-phase 25 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 = 25 kVAV₁ = 10000 VV₂ = 400 V

I_LV = A

5.Hard

A single-phase 250 kVA transformer has a core loss of 750 W and a copper loss of 1875 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 250 kVAP_core = 750 WP_cu,fl = 1875 W

S_η,max = kVA

6.Hard

A single-phase 100 kVA transformer has a core loss of 300 W and a copper loss of 1200 W at rated load. It supplies 75% of its rated kVA at a power factor of 0.9 lagging. Find the total losses P_loss in watts at this load.

S = 100 kVAP_core = 300 WP_cu,fl = 1200 Wx = 0.75pf = 0.9

P_loss = W

Answer key

1. V₂ = 240 V
2. V₂ = 240 V
3. I_HV = 45.45 A
4. I_LV = 62.5 A
5. S_η,max = 158.1 kVA
6. P_loss = 975 W

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