An avionics technician is servicing a step-down transformer in an aircraft subsystem. The … — Armed Services Vocational Aptitude Battery (ASVAB)

An avionics technician is servicing a step-down transformer in an aircraft subsystem. The transformer receives an input voltage of $115\text{ V AC}$ across its primary coil and delivers an output voltage of $23\text{ V AC}$ across its secondary coil. If the primary winding has $750\text{ turns}$ , what is the number of turns on the secondary winding?

Answer: 150 turns

Answer

150 turns

The relationship between primary and secondary voltage and turns in a transformer is

\frac{V_p}{V_s} = \frac{N_p}{N_s}

. Given a primary voltage of

115\text{ V AC}

and a secondary voltage of

23\text{ V AC}

, the transformer has a step-down ratio of

5:1

(

115 / 23 = 5

). Dividing the primary turns (

750

) by

5

gives

150\text{ turns}

for the secondary winding.

Step-by-Step Solution

State the fundamental transformer turns ratio formula relating voltage and winding turns.

\frac{V_p}{V_s} = \frac{N_p}{N_s}

The voltage induced across transformer windings is directly proportional to the number of turns on each winding.

Isolate the secondary turns variable (

N_s

N_s = N_p \times \frac{V_s}{V_p}

Algebraic rearrangement allows direct calculation of the secondary coil turns.

Substitute the given values (

V_p = 115\text{ V AC}

V_s = 23\text{ V AC}

N_p = 750\text{ turns}

) and simplify.

N_s = 750 \times \frac{23}{115} = 750 \times 0.2 = 150\text{ turns}

The voltage reduction factor is

5:1

, meaning the secondary winding must have one-fifth the number of turns of the primary winding.

Key Concept

Transformer turns and voltage ratio relationship

Estimated Time:1m 0s

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