(a) cheaper in cost
(b) lighter in weight
(c) easy to cast owing to its low melting point and is easily available
(d) of low resistivity
Answer: (c) easy to cast owing to its low melting point and is easily available
Explanation:
📖 Detailed Solution
🔹 Aluminium has a relatively low melting point compared to copper and steel.
🔹 Due to this property, it can be easily melted and injected into rotor slots using the die-casting process.
🔹 Aluminium is abundantly available and economical.
🔹 It supports mass production of squirrel cage rotors.
🔹 The die-casting process forms rotor bars and end rings in a single operation, reducing manufacturing time and cost.
🔹 This improves production efficiency and consistency.
👉 Therefore, aluminium is preferred mainly for ease of casting and availability.
⚙️ Various parts related to squirrel cage rotor are:
✔️ Rotor Core
✔️ Aluminium Bars
✔️ End Rings
✔️ Shaft
✔️ Cooling Fan
🔄 Rotor (Die-Cast Aluminium Type):
🔹 Rotor slots are filled with molten aluminium by pressure die-casting.
🔹 Bars and end rings are formed simultaneously.
🔹 Provides good mechanical rigidity.
🔹 Ensures low maintenance operation.
🔹 Suitable for high-speed mass production.
🔹 Commonly used in industrial induction motors.
📌 Key Exam Notes
⭐ Rotor Material → Die-Cast Aluminium
⭐ Main Advantage → Easy Casting + Availability
⭐ Manufacturing Method → Pressure Die-Casting
⭐ Rotor Type → Squirrel Cage
⭐ Cost → Low
📝 Final Summary
📍 Die-cast aluminium is used in induction motor rotors because:
✔️ Low melting point
✔️ Easy manufacturing
✔️ Easily available
✔️ Suitable for mass production
👉 Hence, Option C is Correct.