Question

Why are current limiting reactors usually “Air-cored” rather than “Iron-cored”?

• A. To reduce weight
• B. To improve cooling
• C. To avoid magnetic saturation during heavy fault currents
• D. To decrease the cost of iron

Hint:

Air-cored reactors are used in fault current limiting because air does not saturate even under heavy current conditions.

Answer 1

The Correct Option is C

Concept: Current limiting reactors are used to limit short-circuit current in power systems. During faults, very large current flows through the reactor.

Step 1: If an iron core is used, the magnetic flux increases with current.

Step 2: During heavy fault currents, the iron core may reach magnetic saturation.

Step 3: When saturation occurs, inductance decreases and the reactor cannot limit current effectively.

Step 4: Air does not saturate like iron.

Step 5: Therefore, air-cored reactors maintain nearly constant inductance even during heavy fault currents. Hence, current limiting reactors are air-cored: \[ \boxed{\text{To avoid magnetic saturation during heavy fault currents}} \]