A step-up transformer is designed to have an output voltage of 2 200 V (rms) whe

Question

A step-up transformer is designed to have an output voltage of 2 200 V (rms) when the primary is connected across a 110-V (rms) source (a) If the primary winding has exactly 82 turns, how many turns are required on the secondary? turns (b) If a load resistor across the secondary draws a current of 1.40 A, what is the current in the primary, assuming ideal conditions? (c) If the transformer actually has an efficiency of 88.0%, what is the current in the primary when the secondary current is 1.20 A? Need Help? Read It Watch It

Explanation / Answer

Given,

Vs = 2200 ; vp = 110 V ; Np = 82 ; Ns = ?

a)We know that

Ns/Np = Vs/Vp =>Ns = (Vs/Vp)Np

Ns = (2200/110)82 = 1640

Hence, Ns = 1640 turns

b)We know that,

Vs/Vp = Ip/Is

Ip = (Vs/Vp)Is

Ip = (2200/110)1.4 = 28 A

Hence, Ip = 28 A

c)eta = 88% = 0.88

The current in the primary will be given by:

Ip = (Vs/eta)/Vp = (2200/0.88)/110 = 22.73 A

Hence, Ip = 22.73 A

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