This blog post is from an updated section of Bodine Electric’s Small Motors Handbook. To download this article as a PDF, please click here.
Although commutator and brush assemblies may be used in some types of alternating current (AC) gearmotors and motors (series-/universal wound), brushless induction-type designs are by far the most common and most reliable for industrial AC motors and gearmotors that operate from an AC power source or from an AC speed control (adjustable speed drive).
In an AC induction motor or gearmotor, the stator winding sets up a magnetic field which reacts with the current-carrying conductors of the rotor to produce rotational torques. The rotor currents are induced in the rotor conductors by the stator’s changing magnetic field, rather than by means of a commutator and brushes. This induction action is the central operating principle of AC induction motors.
AC power is commercially supplied in both single-phase and three-phase forms. The essential operating characteristics of AC induction motors and gearmotors will vary according to:
1) winding types (split-phase, shaded-pole, three-phase, etc.), and
2) the number of phases, the frequency, and the voltage of the power source.
2.2 POLYPHASE MOTORS (Two or Three Phases)
The production of a rotating magnetic field can be simply illustrated by considering a two-phase motor with two embedded stator windings for establishing the magnetic fields. Read More…