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 750 turns on its primary winding and 150 turns on its secondary winding. The primary is connected to a 600 V AC supply. Find the secondary voltage V₂.

N₁ = 750N₂ = 150V₁ = 600 V

V₂ = V

2.Easy

An ideal transformer has 1500 turns on its primary winding and 60 turns on its secondary winding. The primary is connected to a 5750 V AC supply. Find the secondary voltage V₂.

N₁ = 1500N₂ = 60V₁ = 5750 V

V₂ = V

3.Medium

A single-phase 250 kVA, 2400/240 V transformer operates at its rated load. Treat it as ideal. Find the current I_LV in the low-voltage winding.

S = 250 kVAV₁ = 2400 VV₂ = 240 V

I_LV = A

4.Medium

A 5 Ω resistor is connected across the secondary winding of an ideal transformer with a turns ratio N₁:N₂ = 6:1. Find the resistance R_1′ seen looking into the primary winding.

N₁:N₂ = 6:1R_L = 5 Ω

R_1′ = Ω

5.Hard

A single-phase 500 kVA transformer has a core loss of 3000 W and a copper loss of 9000 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 500 kVAP_core = 3000 WP_cu,fl = 9000 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. At what load S_η,max, in kVA, is its efficiency highest?

S = 100 kVAP_core = 300 WP_cu,fl = 1200 W

S_η,max = kVA

Answer key

1. V₂ = 120 V
2. V₂ = 230 V
3. I_LV = 1042 A
4. R_1′ = 180 Ω
5. S_η,max = 288.7 kVA
6. S_η,max = 50 kVA

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