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In electrical engineering, the armature is the winding (or set of windings) of an electric machine which carries alternating current. [1] The armature windings conduct AC even on DC machines, due to the commutator action (which periodically reverses current direction) or due to electronic commutation, as in brushless DC motors .
A hacksaw blade is commonly used as a feeler. The alternating magnetic field induced by a shorted armature is strong at the surface of the armature, and when the feeler is lightly touched to the iron core of an armature winding, small currents are induced in the feeler that generate a third alternating magnetic field surrounding the feeler.
For a single armature winding, when the shaft has made one-half complete turn, the winding is now connected so that current flows through it in the opposite of the initial direction. In a motor, the armature current causes the fixed magnetic field to exert a rotational force, or a torque, on the winding to make it turn. In a generator, the ...
The stator consists of field windings while the rotor (also called the armature) consists of an armature winding. [4] When both the armature and the field windings are excited by a DC supply, current flows through the windings and a magnetic flux proportional to the current is produced. When the flux from the field interacts with the flux from ...
The windings usually have multiple turns around the core, and in large motors there can be several parallel current paths. The ends of the wire winding are connected to a commutator. The commutator allows each armature coil to be energized in turn and connects the rotating coils with the external power supply through brushes.
If the motor is stalled, the current is limited only by the total resistance of the windings and the torque can be very high, and there is a danger of the windings becoming overheated. The counter-EMF aids the armature resistance to limit the current through the armature. When power is first applied to a motor, the armature does not rotate.
Since the shapes of all windings are the same, the amount of the lines of force will be cut at the same amount in the same direction at the same time in all windings. This creates in phase AC output for these 4 windings. As a result, the output voltage is increased 4 time as shown in the sine wave in the diagram. [4]
In severe cases, this can lead to "birdnesting" as the windings contact the motor housing and eventually break loose from the armature entirely and uncoil. Bird-nesting (the centrifugal ejection of the armature's windings) due to overspeed can occur either in operating traction motors of powered locomotives or in traction motors of dead-in ...