Question

The efficiency of a power transformer is of the order of :

• A. 60%
• B. 70%
• C. 98%
• D. 80%

Hint:

Power transformers are among the most efficient electrical machines. Typical efficiency: \[ 95%-99% \] Large transformers commonly operate near: \[ 98% \]

Answer 1

The Correct Option is C

Concept: Power transformers are highly efficient electrical machines. Since transformers have:
• no rotating parts,
• very small mechanical losses,
• low copper and iron losses, their efficiency is extremely high. Large power transformers generally have efficiencies between: \[ 95% \text{ to } 99% \] and commonly around: \[ 98% \]

Step 1: Understanding transformer efficiency. Efficiency is: \[ \eta=\frac{\text{Output Power}}{\text{Input Power}}\times100 \] For transformers:
• copper losses are minimized,
• core losses are reduced using silicon steel laminations,
• friction and windage losses are absent. Therefore efficiency becomes very high.

Step 2: Checking each option carefully.
• \(60%\) \(\rightarrow\) Too low for power transformers
• \(70%\) \(\rightarrow\) Also too low
• \(98%\) \(\rightarrow\) Typical practical value for power transformers
• \(80%\) \(\rightarrow\) Lower than practical transformer efficiency

Step 3: Selecting the correct answer. Hence the efficiency of a power transformer is generally of the order: \[ \boxed{98%} \] Therefore the correct option is: \[ \boxed{(3)} \]