Editing Linear induction motor (section)

==Forces==

===Thrust===
[[File:Couple glissement MAs.svg|thumb|right|Thrust generated as a function of slip]]
The drive generated by linear induction motors is somewhat similar to conventional induction motors; the drive forces show a roughly similar characteristic shape relative to slip, albeit modulated by end effects.<ref name=force>Force Analysis of Linear Induction Motor for Magnetic Levitation System 14th International Power Electronics and Motion Control Conference, EPE-PEMC 2010</ref>

Equations exist for calculating the thrust of a motor.<ref>Journal of Modern Transportation June 2012, Volume 20, Issue 2, pp 76–81 A novel method to calculate the thrust of linear induction motor based on instantaneous current value</ref>

===End effect===
Unlike a circular induction motor, a linear induction motor shows 'end effects'. These end effects include losses in performance and efficiency that are believed to be caused by magnetic energy being carried away and lost at the end of the primary by the relative movement of the primary and secondary.

With a short secondary, the behaviour is almost identical to a rotary machine, provided it is at least two poles long but with a short primary reduction in thrust that occurs at low slip (below about 0.3) until it is eight poles or longer.<ref name=personalView>linear Electric Machines- A Personal View ERIC R. LAITHWAITE, FELLOW, IEEE, PROCEEDINGS OF THE IEEE, VOL. 63, NO. 2, FEBRUARY 1975</ref>

However, because of end effects, linear motors cannot 'run light' -- normal induction motors are able to run the motor with a near synchronous field under low load conditions. In contrast, end effects create much more significant losses with linear motors.<ref name=personalView/>

===Levitation===
[[File:Linear motor torque curve.png|thumb|Levitation and thrust force curves of a linear motor]]
In addition, unlike a rotary motor, an [[electrodynamic levitation]] force is shown, this is zero at zero slip, and gives a roughly constant amount of force/gap as slip increases in either direction. This occurs in single sided motors, and levitation will not usually occur when an iron backing plate is used on the secondary, since this causes an attraction that overwhelms the lifting force.<ref name=force/>
{{clear}}