Induction motor can be fed from

Question

Examoogle · Accepted Answer

either rotor or stator

Explanation: An induction motor is based on the principle of electromagnetic induction between two magnetically coupled circuits (stator and rotor). Therefore, the energy can be supplied to either winding, provided the other is short-circuited or closed through an impedance to allow current flow and torque production.

Working Principle: The principle relies on the relative motion between the magnetic field and the conductors. When the stator is fed, it creates a rotating magnetic field (RMF) that induces current in the rotor. If the rotor is fed instead, the rotor windings must be configured to create an RMF that interacts with the stationary (shorted) stator conductors to produce equivalent electromagnetic torque.

Key Formulas: $s = \frac{N_s - N_r}{N_s}$ — Slip calculation formula; $f_r = s \cdot f_s$ — Rotor frequency under slip condition

Key Points: Induction motors are essentially generalized transformers with a moving secondary.; The air gap flux is produced by the excitation current in whichever winding acts as the primary.; For standard induction motors, the stator is usually the primary and rotor is the secondary for mechanical design reasons.; Feeding the rotor requires slip rings or specialized collector systems if it is to rotate relative to the source.

Advantages: Flexibility in machine design; Allows for speed control via rotor-side frequency injection (Doubly Fed Induction Machines)

Disadvantages: Complexity in physical connection to the rotating part; Increased insulation requirements for rotor windings

Applications: Doubly Fed Induction Generators (DFIG) in Wind Turbines; Slip ring induction motor starters; Frequency converters

Additional Info: In a Doubly Fed Induction Generator (DFIG), both stator and rotor are connected to different power sources to control reactive power and torque.. Options B and C are partially correct in context of standard motors, but Option A is the comprehensive correct choice.

Answer: A is correct — Induction motors rely on relative magnetic coupling, allowing excitation of either the stator or the rotor.

Exam Tip: Always remember that an induction motor is a transformer with a rotating secondary; the reciprocity of induction holds true regardless of which side is energized.

Related Questions

Discussion (0)