Question

AC machines should have proper _______ in order to limit the operating temperature.

• A. Voltage rating
• B. Current rating
• C. Speed
• D. kW rating

Hint:

The current rating of an AC machine is critical for managing heating. Overloading the machine beyond its rated current can lead to excessive temperature rise.

Answer 1

The Correct Option is B

Step 1: The operating temperature of an AC machine is primarily influenced by the losses, such as copper losses (\( I^2R \)) and iron losses. 
Step 2: Copper losses are directly proportional to the current flowing through the windings. A higher current leads to increased resistive heating, raising the temperature. 
Step 3: If the machine operates beyond its rated current, it will overheat, possibly damaging the insulation and reducing the overall efficiency. 
Step 4: A proper current rating ensures that the machine operates within safe thermal limits, maintaining its efficiency and prolonging its service life.