THE MOTOR STRUCTURE

All motors have a similar basic construction. Each has two main parts:

            1.         The stator.
            2.         The rotor.

The stator is normally mounted on the frame.  This frame is usually cylindrical in shape.  The field poles with field windings on them are part of the stator.  The identification plate is also mounted on the stator. The frame has end bells or plates attached to it. These hold the bearings.  When the rotor shaft journals are mounted in the bearings, the bells support the rotor.

The rotor is mounted on a shaft, which has two journal bearings, one at each end.  The bearings are accurately machined to provide the proper amount of endplay for the rotor.  There is a clearance of .001 to .002 between the motor shaft and the bearing

The windings are insulated copper wire.  This insulation is usually a polyester material.  It is resistant to moisture and has considerable dielectric and mechanical strength.

Both alternating current (AC) and direct current (DC) may be used to operate electric motors.  Following motor types are most commonly used: -


AC - Single phase

            Split phase induction.
            Capacitor-start induction.
            Capacitor-start, capacitor run.
            Shaded pole.
            Universal.
            Repulsion.

AC - Three phase

            Squirrel cage induction
            Wound rotor induction
            Synchronous

DC -    Series
            Shunt
            Compound

Today, the capacitor motor is being used on most household applications.  It is the most popular single-phase machine.