🔍 Key Concepts

• Synchronous speed of an AC induction motor and its formula • How the number of stator poles affects motor speed in a fixed-frequency system • Which motor characteristics are affected by rotor resistance vs. which control speed steps

💭 Think About

• In a fixed frequency system, which quantities in the synchronous speed formula can practically be changed during operation? • Which of the answer choices directly changes the number of magnetic poles seen by the rotating field? • Which options mainly affect starting characteristics (like starting torque or inrush current) rather than establishing distinct operating speeds?

✅ Before You Answer

• Recall the formula for synchronous speed and identify the variables that can change: frequency and number of poles • Check which choice specifically mentions a way to vary the number of stator poles (or pole groups) to obtain multiple discrete speeds • Eliminate options that refer to starting conditions (locked-rotor current, rotor resistance) rather than establishing different synchronous speeds in a fixed-frequency system