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 60 turns on its primary winding and 3000 turns on its secondary winding. The primary is connected to a 120 V AC supply. Find the secondary voltage V₂.

N₁ = 60N₂ = 3000V₁ = 120 V

V₂ = V

2.Easy

An ideal transformer must step 2400 V down to 120 V. Its primary winding has 2400 turns. How many turns N₂ does the secondary winding need?

V₁ = 2400 VV₂ = 120 VN₁ = 2400

N₂ =

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 2:1 has 480 V applied to its primary winding. A 4 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 2:1V₁ = 480 VR_L = 4 Ω

I₁ = A

4.Medium

A single-phase 50 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 = 50 kVAV₁ = 11000 VV₂ = 400 V

I_HV = A

5.Hard

A single-phase 250 kVA transformer has a core loss of 1500 W and a copper loss of 4500 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 250 kVAP_core = 1500 WP_cu,fl = 4500 W

S_η,max = kVA

6.Hard

A single-phase 25 kVA transformer has a core loss of 125 W and a copper loss of 312.5 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 25 kVAP_core = 125 WP_cu,fl = 312.5 W

S_η,max = kVA

Answer key

1. V₂ = 6000 V
2. N₂ = 120
3. I₁ = 30 A
4. I_HV = 4.545 A
5. S_η,max = 144.3 kVA
6. S_η,max = 15.81 kVA

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