Editing Electric motor (section)

==Components==
[[File:Stator_and_rotor_by_Zureks.JPG|right|thumb|[[rotor (electric)|Rotor]] (left) and [[stator]] (right)]]

An electric motor has two mechanical parts: the rotor, which moves, and the stator, which does not. Electrically, the motor consists of two parts, the field magnets and the armature, one of which is attached to the rotor and the other to the stator. Together they form a [[magnetic circuit]].<ref name="Scarpino2">{{cite book|last1=Scarpino|first1=Matthew|url=https://books.google.com/books?id=FpEFCwAAQBAJ&q=%22electric+motor%22+armature+lorentz+field+winding|title=Motors for Makers: A Guide to Steppers, Servos, and Other Electrical Machines|date=2015|publisher=Que|isbn=978-0-13-403132-3|doi=|id=}} Section 1.2.2</ref> The magnets create a magnetic field that passes through the armature. These can be [[electromagnet]]s or [[permanent magnet]]s. The field magnet is usually on the stator and the armature on the rotor, but these may be reversed.[[File:Salient-pole_rotor.png|right|thumb|Salient-pole rotor]]

===Rotor===
{{main|Rotor (electric)}}

The rotor is the moving part that delivers the mechanical power. The rotor typically holds conductors that carry currents, on which the magnetic field of the stator exerts force to turn the shaft.<ref name="Induction2">{{cite magazine|author=<!--Staff writer(s); no by-line.-->|date=March 7, 2015|title=Permanent magnet vs. induction motors|url=https://www.turbomachinerymag.com/view/permanent-magnet-vs-induction-motors|magazine=Turbomachinery International|location=United States|publisher=MJH life sciences|access-date=November 8, 2021}}</ref>

===Stator===
{{main|Stator}}

The stator surrounds the rotor, and usually holds field magnets, which are either [[electromagnet]]s (wire windings around a ferromagnetic iron core) or [[permanent magnet]]s. These create a [[magnetic field]] that passes through the rotor armature, exerting force on the rotor windings. The stator core is made up of many thin metal sheets that are insulated from each other, called laminations. These laminations are made of [[electrical steel]], which has a specified magnetic permeability, hysteresis, and saturation. Laminations reduce losses that would result from induced circulating eddy currents that would flow if a solid core were used. Mains powered AC motors typically immobilize the wires within the windings by impregnating them with varnish in a vacuum. This prevents the wires in the winding from vibrating against each other which would abrade the wire insulation and cause premature failures. Resin-packed motors, used in deep well submersible pumps, washing machines, and air conditioners, [[Potting (electronics)|encapsulate]] the stator in plastic [[resin]] to prevent corrosion and/or reduce conducted noise.<ref>{{Cite web|title=Resin-Packed Motors|url=https://www.nidec.com/en/technology/casestudy/resin_pack_motor/|website=Nidec Corporation}}</ref>

=== Gap ===
{{main|Air gap (magnetic)}}

An air gap between the stator and rotor allows it to turn. The width of the gap has a significant effect on the motor's electrical characteristics. It is generally made as small as possible, as a large gap weakens performance. Conversely, gaps that are too small may create friction in addition to noise.

===Armature===
{{See also|Electromagnetic coil}}
The [[Armature (electrical)|armature]] consists of wire windings on a [[ferromagnetic]] core. Electric current passing through the wire causes the [[magnetic field]] to exert a force ([[Lorentz force]]) on it, turning the rotor. Windings are [[Electromagnetic coil|coiled]] wires, wrapped around a laminated, soft, iron, [[Magnetic core|ferromagnetic core]] so as to form magnetic poles when energized with current.

Electric machines come in salient- and nonsalient-pole configurations. In a salient-pole motor the rotor and stator ferromagnetic cores have projections called poles that face each other. Wire is wound around each pole below the pole face, which become north or south poles when current flows through the wire. In a nonsalient-pole (distributed field or round-rotor) motor, the ferromagnetic core is a smooth cylinder, with the windings distributed evenly in slots around the circumference. Supplying alternating current in the windings creates poles in the core that rotate continuously.<ref name="Mortensen (1949)2">{{cite book|last1=Mortensen|first1=S.H.|title=§7-1 'General Picture of a Synchronous Machine' in Sec. 7 – Alternating-Current Generators and Motors|last2=Beckwith|first2=S.|pages=646–47, figs. 7–1 & 7–2}} in {{harvnb|Knowlton|1949}}</ref> A [[shaded-pole motor]] has a winding around part of the pole that delays the phase of the magnetic field for that pole.

===Commutator===
{{main|Commutator (electric)}}
[[File:Universal_motor_commutator.jpg|thumb|[[commutator (electric)|Commutator]] in a [[universal motor]] from a vacuum cleaner. Parts: ''(A)'' commutator, ''(B)'' [[brush (electric)|brush]]]]

A [[commutator (electric)|commutator]] is a rotary [[switch|electrical switch]] that supplies current to the rotor. It periodically reverses the flow of current in the rotor windings as the shaft rotates. It consists of a cylinder composed of multiple metal contact segments on the [[armature (electrical engineering)|armature]]. Two or more [[electrical contacts]] called ''[[brush (electric)|brushes]]'' made of a soft conductive material like [[carbon]] press against the commutator. The brushes make sliding contact with successive commutator segments as the rotator turns, supplying current to the rotor. The windings on the rotor are connected to the commutator segments. The commutator reverses the [[current (electricity)|current]] direction in the rotor windings with each half turn (180°), so the torque applied to the rotor is always in the same direction.{{sfn|Hameyer|2001|p=62}} Without this reversal, the direction of torque on each rotor winding would reverse with each half turn, stopping the rotor. Commutated motors have been mostly replaced by [[brushless DC motor|brushless motors]], [[permanent magnet motor]]s, and [[induction motor]]s.

=== Shaft ===
The motor shaft extends outside of the motor, where it satisfies the load. Because the forces of the load are exerted beyond the outermost bearing, the load is said to be overhung.<ref name=":1">{{cite web |date=2017 |title=How belt drives impact overhung load |url=http://designcenter.gates.com/wp-content/uploads/2015/05/Gates-How-Belt-Drives-Impact-Overhung-Load-White-Paper.pdf |archive-url=https://web.archive.org/web/20160222054609/http://designcenter.gates.com/wp-content/uploads/2015/05/Gates-How-Belt-Drives-Impact-Overhung-Load-White-Paper.pdf |archive-date=February 22, 2016 |access-date=July 28, 2017 |publisher=Gates Corporation}}</ref>

===Bearings===
{{main|Bearing (mechanical)}}

The rotor is supported by [[Bearing (mechanical)|bearings]], which allow the rotor to turn on its axis by transferring the force of axial and radial loads from the shaft to the motor housing.<ref name=":1" />