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 80 turns on its primary winding and 400 turns on its secondary winding. The primary is connected to a 240 V AC supply. Find the secondary voltage V₂.

N₁ = 80N₂ = 400V₁ = 240 V

V₂ = V

2.Easy

An ideal transformer must step 800 V down to 400 V. Its primary winding has 50 turns. How many turns N₂ does the secondary winding need?

V₁ = 800 VV₂ = 400 VN₁ = 50

N₂ =

3.Medium

A single-phase 500 kVA, 10000/400 V transformer operates at its rated load. Treat it as ideal. Find the current I_HV in the high-voltage winding.

S = 500 kVAV₁ = 10000 VV₂ = 400 V

I_HV = A

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 20:1 has 2400 V applied to its primary winding. A 4 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 20:1V₁ = 2400 VR_L = 4 Ω

I₁ = A

5.Hard

A single-phase 25 kVA transformer has a core loss of 75 W and a copper loss of 112.5 W at rated load. It supplies 25% of its rated kVA at a power factor of 0.95 lagging. Find the total losses P_loss in watts at this load.

S = 25 kVAP_core = 75 WP_cu,fl = 112.5 Wx = 0.25pf = 0.95

P_loss = W

6.Hard

A single-phase 100 kVA transformer has a core loss of 600 W and a copper loss of 1800 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 100 kVAP_core = 600 WP_cu,fl = 1800 W

S_η,max = kVA

Answer key

1. V₂ = 1200 V
2. N₂ = 25
3. I_HV = 50 A
4. I₁ = 1.5 A
5. P_loss = 82.03 W
6. S_η,max = 57.74 kVA

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