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 1600 turns on its primary winding and 100 turns on its secondary winding. The primary is connected to a 3840 V AC supply. Find the secondary voltage V₂.

N₁ = 1600N₂ = 100V₁ = 3840 V

V₂ = V

2.Easy

An ideal transformer must step 1920 V down to 120 V. Its primary winding has 960 turns. How many turns N₂ does the secondary winding need?

V₁ = 1920 VV₂ = 120 VN₁ = 960

N₂ =

3.Medium

A single-phase 15 kVA, 6600/230 V transformer operates at its rated load. Treat it as ideal. Find the current I_HV in the high-voltage winding.

S = 15 kVAV₁ = 6600 VV₂ = 230 V

I_HV = A

4.Medium

An amplifier with an output resistance of 576 Ω drives a 16 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 576 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 576 ΩR_L = 16 Ω

a =

5.Hard

A single-phase 75 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 = 75 kVAP_core = 600 WP_cu,fl = 1500 W

S_η,max = kVA

6.Hard

A single-phase 200 kVA transformer has a core loss of 1200 W and a copper loss of 2400 W at rated load. It supplies 25% of its rated kVA at a power factor of 0.9 lagging. Find the total losses P_loss in watts at this load.

S = 200 kVAP_core = 1200 WP_cu,fl = 2400 Wx = 0.25pf = 0.9

P_loss = W

Answer key

1. V₂ = 240 V
2. N₂ = 60
3. I_HV = 2.273 A
4. a = 6
5. S_η,max = 47.43 kVA
6. P_loss = 1350 W

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