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 960 V down to 120 V. Its primary winding has 960 turns. How many turns N₂ does the secondary winding need?

V₁ = 960 VV₂ = 120 VN₁ = 960

N₂ =

2.Easy

An ideal transformer has 150 turns on its primary winding and 7500 turns on its secondary winding. The primary is connected to a 230 V AC supply. Find the secondary voltage V₂.

N₁ = 150N₂ = 7500V₁ = 230 V

V₂ = V

3.Medium

An amplifier with an output resistance of 2304 Ω drives a 16 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 2304 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 2304 ΩR_L = 16 Ω

a =

4.Medium

A single-phase 10 kVA, 4800/240 V transformer operates at its rated load. Treat it as ideal. Find the current I_LV in the low-voltage winding.

S = 10 kVAV₁ = 4800 VV₂ = 240 V

I_LV = A

5.Hard

A single-phase 100 kVA transformer has a core loss of 300 W and a copper loss of 450 W at rated load. It supplies 75% of its rated kVA at a power factor of 0.85 lagging. Find the total losses P_loss in watts at this load.

S = 100 kVAP_core = 300 WP_cu,fl = 450 Wx = 0.75pf = 0.85

P_loss = W

6.Hard

A single-phase 50 kVA transformer has a core loss of 400 W and a copper loss of 800 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 50 kVAP_core = 400 WP_cu,fl = 800 W

S_η,max = kVA

Answer key

1. N₂ = 120
2. V₂ = 11500 V
3. a = 12
4. I_LV = 41.67 A
5. P_loss = 553.1 W
6. S_η,max = 35.36 kVA

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