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 640 turns on its primary winding and 40 turns on its secondary winding. The primary is connected to a 3840 V AC supply. Find the secondary voltage V₂.

N₁ = 640N₂ = 40V₁ = 3840 V

V₂ = V

2.Easy

An ideal transformer has 120 turns on its primary winding and 960 turns on its secondary winding. The primary is connected to a 120 V AC supply. Find the secondary voltage V₂.

N₁ = 120N₂ = 960V₁ = 120 V

V₂ = V

3.Medium

A 50 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 = 50 Ω

R_1′ = Ω

4.Medium

A 16 Ω resistor is connected across the secondary winding of an ideal transformer with a turns ratio N₁:N₂ = 10:1. Find the resistance R_1′ seen looking into the primary winding.

N₁:N₂ = 10:1R_L = 16 Ω

R_1′ = Ω

5.Hard

A single-phase 200 kVA transformer has a core loss of 800 W and a copper loss of 1200 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 200 kVAP_core = 800 WP_cu,fl = 1200 W

S_η,max = kVA

6.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

Answer key

1. V₂ = 240 V
2. V₂ = 960 V
3. R_1′ = 1800 Ω
4. R_1′ = 1600 Ω
5. S_η,max = 163.3 kVA
6. S_η,max = 126.5 kVA

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