Which statement best describes AC induction motors?

Which statement best describes AC induction motors?

• A. They have no brushes or armature
• B. They use carbon brushes for commutation
• C. They require a commutator
• D. They rely on external magnets

Answer: (A)

AC induction motors transfer power to the rotor by electromagnetic induction from a rotating magnetic field created by the stator windings fed with AC. Because the rotor is not electrically connected to the supply, there are no brushes and no commutator needed. This makes induction motors robust and low-maintenance. Carbon brushes and a commutator imply a DC-type machine or a motor with a wound-rotor that still requires commutation, which induction motors do not use. They do not rely on external magnets for normal operation (that would describe permanent-magnet or some synchronous machines), whereas an induction motor achieves rotation purely through induced rotor currents driven by the stator’s rotating field.

AC induction motors transfer power to the rotor by electromagnetic induction from a rotating magnetic field created by the stator windings fed with AC. Because the rotor is not electrically connected to the supply, there are no brushes and no commutator needed. This makes induction motors robust and low-maintenance.

Carbon brushes and a commutator imply a DC-type machine or a motor with a wound-rotor that still requires commutation, which induction motors do not use. They do not rely on external magnets for normal operation (that would describe permanent-magnet or some synchronous machines), whereas an induction motor achieves rotation purely through induced rotor currents driven by the stator’s rotating field.