Armature (electrical engineering)

In electrical engineering, an armature is one of the two principal electrical components of an electromechanical machine--a motor or generator. The other is the "field" winding, field magnet. The role of the "field" component is simply to create a magnetic field (magnetic flux) for the armature to interact with, so this component can comprise either permanent magnets, or electromagnets formed by a conducting coil. The armature, in contrast, must carry current so it is always a conductor or a conductive coil, oriented normal to both the field and to the direction of motion, torque (rotating machine), or force (linear machine). The armature's role is two-fold: (a) to carry current crossing the field, thus creating shaft torque (in a rotating machine) or force (in a linear machine), and (b) to generate an electromotive force ("EMF").

In the armature, an electromotive force ("EMF") is created by the relative motion of the armature and the field. When the machine is acting as a motor, this EMF opposes the armature current, and the armature converts electrical power to mechanical torque (and power, unless the machine is stalled) and transfers it to the load via the shaft. When the machine is acting as a generator, the armature EMF drives the armature current, and shaft mechanical power is converted to electrical power and transferred to the load. (In an induction generator, these distinctions are blurred, since the generated power is drawn from the stator, which would normally be considered the field.)

A growler is used to check the armature for shorts, opens and grounds.

Terminology

The parts of an alternator or related equipment can be expressed in either mechanical terms or electrical terms. Although distinctly separate, these two sets of terminology are frequently used interchangeably or in combinations that include one mechanical term and one electrical term. This may cause confusion when working with compound machines such as brushless alternators, or in conversation among people who are accustomed to work with differently configured machinery.

"Mechanical"
Rotor: The rotating part of an alternator, generator, dynamo or motor.
Stator: The stationary part of an alternator, generator, dynamo or motor

"Electrical"
Armature: The power-producing component of an alternator, generator, dynamo or motor. The armature can be on either the rotor or the stator.
Field: The magnetic field component of an alternator, generator, dynamo or motor. The field can be on either the rotor or the stator and can be either an electromagnet or a permanent magnet.

In alternating current machines, the armature is usually stationary (the "stator"). In DC rotating machines other than "brushless DC" machines, it is usually rotating (the "rotor").

The pole piece of a permanent magnet or electromagnet and the moving, iron part of a solenoid, especially if the latter acts as a switch or relay, may also be referred to as armatures

See also

*Armature reaction drop
*Electric generator
*Stator
*CommutatorArmature Reaction in a DC machine: In a dc machine the main field is produced by field coils.In both the generating and motoring modes the armature carries current and a magnetic field is established which is called the armature flux. The effect of armature flux on the main field is called the armature reaction.

The armature reaction 1) Demagnetizes the main field2) Cross magnetizes the main field.

The demagnetizing effect can be overcome by adding extra ampere turns on the main field.The cross magnetizing effect can be reduced by having common poles.

External links

* [http://www.swigercoil.com/upload/newsletter/dcarmature.pdf Example Diagram of an Armature Coil and data used to specify armature coil parameters]