Editing Synchronous motor (section)

{{Short description|Type of AC motor}}
[[File:Single phase low power synchronous clock motor with removed cover.jpg|thumb|Miniature synchronous motor used in analog clocks. The rotor is made of permanent magnet.]]
[[File:Synchronmot.jpg|thumb|upright|Small synchronous motor with integral stepdown gear from a microwave oven]]

A '''synchronous electric motor''' is an [[AC motor|AC electric motor]] in which, at [[steady state]],<ref name=Fitzgerald1971b>
{{cite book
  | last = Fitzgerald
  | first = A. E.
  | author2 = Charles Kingsley Jr.
  | author3 = Alexander Kusko
  | title = Electric Machinery, 3rd Ed.
  | publisher = McGraw-Hill
  | year = 1972 
  | location = USA
  | pages = 283–330
  | chapter = Chapter 6, Synchronous machines, steady state
  | id = Library of Congress Catalog No. 70-137126
}}</ref> the rotation of the shaft is synchronized with the [[utility frequency|frequency of the supply current]]; the rotation period is exactly equal to an integer number of [[alternating current|AC]] cycles. Synchronous motors use [[electromagnet]]s as the [[stator]] of the motor which create a [[rotating magnetic field|magnetic field that rotates]] in time with the oscillations of the current. The [[rotor (electric)|rotor]] with permanent magnets or electromagnets turns in step with the stator field at the same rate and as a result, provides the second synchronized rotating magnet field. [[Brushless wound-rotor doubly fed electric machine|Doubly fed]] synchronous motors use independently-excited multiphase AC electromagnets for both rotor and stator.<ref>{{cite web | url=https://en.engineering-solutions.ru/motorcontrol/pmsm/ | title=Permanent Magnet Synchronous Motor }}</ref>

Synchronous and [[induction motor]]s are the most widely used AC motors. Synchronous motors rotate at a rate locked to the line frequency since they do not rely on induction to produce the rotor's magnetic field. Induction motors require ''[[Slip (motors)|slip]]'': the rotor must rotate at a frequency slightly slower than the AC alternations in order to induce current in the rotor.

Small synchronous motors are used in timing applications such as in [[Electric clock#Synchronous clock|synchronous clocks]], [[timer]]s in appliances, [[tape recorder]]s and precision [[servomechanism]]s in which the motor must operate at a precise speed; accuracy depends on the [[utility frequency|power line frequency]], which is carefully controlled in large interconnected grid systems.

Synchronous motors are available in self-excited, fractional<ref name="Fitzgerald1971a" /> to industrial sizes.<ref name="Fitzgerald1971b" /> In the fractional power range, most synchronous motors are used to provide precise constant speed. These machines are commonly used in analog electric clocks, timers and related devices.

In typical industrial sizes, the synchronous motor provides an efficient means of converting AC energy to work ([[electrical efficiency]] above 95% is normal for larger sizes){{sfn | Jordan | 2013 | p=106}} and it can operate at leading or unity [[power factor]] and thereby provide power-factor correction.{{citation needed|date=September 2023}}

Synchronous motors fall under the category of ''synchronous machines'' that also includes [[synchronous generator]]s. [[Electric generator|Generator]] action occurs if the field poles are "driven ahead of the resultant air-gap flux by the forward motion of the [[prime mover (engine)|prime mover]]". [[Electric motor|Motor]] action occurs if the field poles are "dragged behind the resultant air-gap flux by the retarding [[torque]] of a shaft [[Electrical load|load]]".<ref name=Fitzgerald1971b/><!-- p. 287 -->

{{Toclimit}}