Question

Identify the type of centrifugal fan having non-over loading power characteristics

• A. Forward bladed centrifugal fan
• B. Radial bladed centrifugal fan
• C. Backward bladed centrifugal fan
• D. Axial flow fan

Hint:

Remember the key safety feature:
- Forward blades = Power keeps rising = Overloading (bad).
- Backward blades = Power peaks and then drops = Non-overloading (good).
This is a major reason why backward-bladed fans are very common in main mine ventilation systems.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
We need to identify the type of centrifugal fan that has a "non-overloading" power characteristic.

Step 2: Detailed Explanation:
The power characteristic of a fan is the relationship between the power it consumes and the volume of air it moves.
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Overloading Characteristic: This means the power consumed by the fan motor continuously increases as the airflow quantity increases (which happens when the mine resistance decreases).
If the resistance becomes very low, the fan will try to move a huge amount of air, and the power demand can exceed the motor's rating, causing it to "overload" and potentially burn out.

Forward-bladed and

Radial-bladed centrifugal fans typically exhibit this overloading characteristic.
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Non-overloading Characteristic: This means the power consumption curve reaches a peak at some airflow quantity and then decreases as the quantity increases further.
This is a very desirable safety feature.
It ensures that no matter how low the mine resistance becomes, the power required by the fan will never exceed a certain maximum value, which can be matched to the motor's rating.

Backward-bladed and backward-curved centrifugal fans are known for this self-limiting, non-overloading power characteristic.

Step 3: Final Answer:
The backward-bladed centrifugal fan has non-overloading power characteristics.
This corresponds to option (C).