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 must step 9200 V down to 230 V. Its primary winding has 1600 turns. How many turns N₂ does the secondary winding need?

V₁ = 9200 VV₂ = 230 VN₁ = 1600

N₂ =

2.Easy

An ideal transformer has 160 turns on its primary winding and 80 turns on its secondary winding. The primary is connected to a 480 V AC supply. Find the secondary voltage V₂.

N₁ = 160N₂ = 80V₁ = 480 V

V₂ = V

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 5:1 has 1200 V applied to its primary winding. An 8 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 5:1V₁ = 1200 VR_L = 8 Ω

I₁ = A

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 4:1 has 480 V applied to its primary winding. A 60 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 4:1V₁ = 480 VR_L = 60 Ω

I₁ = A

5.Hard

A single-phase 100 kVA transformer has a core loss of 800 W and a copper loss of 1600 W at rated load. It supplies 75% of its rated kVA at a power factor of 0.95 lagging. Find the total losses P_loss in watts at this load.

S = 100 kVAP_core = 800 WP_cu,fl = 1600 Wx = 0.75pf = 0.95

P_loss = W

6.Hard

A single-phase 75 kVA transformer has a core loss of 450 W. At rated load and a power factor of 0.85 lagging its efficiency is 98%. Find the full-load copper loss P_cu,fl in watts.

S = 75 kVAP_core = 450 Wpf = 0.85η = 98%

P_cu,fl = W

Answer key

1. N₂ = 40
2. V₂ = 240 V
3. I₁ = 6 A
4. I₁ = 0.5 A
5. P_loss = 1700 W
6. P_cu,fl = 851 W

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