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Understanding of Linear Induction Motor

By Cayla | Published on Sep 16,2015

Guide: The linear motor is a power driver device that directly transfer electrical energy to linear motion mechanical power. It eliminates the need for a large number of intermediate transmission mechanism, speed up the reflect speed of system , improve system accuracy, so it is widely used in industry. Linear motor according to the structure can be divided; the flat unilateral, bilateral flat, disc-type, cylindrical type (or tube) and so on; according to the principle it can be divided: DC motor, asynchronous motor, synchronous motor and step motor.

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Following is a brief introduction of simple structure, easy use, reliable operation linear induction motor.

Structure of linear induction motor includes stator, rotor and support wheel for linear motion. In order to ensure there is good electromagnetic field coupling between stator and mover in the stroke range, core length range of stator and mover is unequal. The stator can be made short and long stator. Due to the high cost of long stator structure, high operating costs, so it is rarely used. Linear motor is the same as rotating magnetic field, the stator core is folded by the silicon, surface has opened a gullet; slot embedded three-phase, two-phase or single-phase windings; single-phase linear induction motor can be made to shaded pole, but also through capacitive phase shift. Linear induction motor mover has three forms:

(1) Magnetic mover:

mover is made of a conductive material (steel), play both the role of the magnetic circuit and electric conduction as a cage-type promoter.

(2) Non-magnetic mover:

the mover is made of non-magnetic material (copper), is made mainly from the conductive effect, this form of linear induction motor there is a the larger air gap in, the excitation current and the loss is large.

(3) The magnetic material surface of mover

It is covered with a layer of conductive material, magnetic material only play a role in electric conduction as magnetic circuit; covering the conductive material for the squirrel cage winding.

Due to linear induction motor with magnetic mover, it's structure is simple. the movers are not only used as magnetic, conductive material, and even can be used as structural components, it has broad application prospects.


The working of linear induction motor is the same as rotary induction motor. The stator windings are connected to AC power, after poly-phase alternating current being generated, a steady magnetic field traveling wave is produced in the air gap (when a rotating magnetic field is large radius, It became the traveling wave magnetic field of linear motion). The magnetic field works along air gap as straight line, while the mover conductor induced electromotive force, and generates a current, the current and the traveling magnetic field interaction, thus generating induction driving force and make the mover traveling along wave direction as straight line. If the linear induction motor stator windings to change power phase sequence, direction of movement of the traveling magnetic field will in turn, according to this principle, can make a linear induction motor for reciprocating linear motion.

Linear Induction Motor is mainly used in high power linear motion mechanism, such as the automatic door opening and closing device, lifting, transfer and lifting machinery and equipment, drive vehicles, especially for high-speed and over-speed transportation. Because traction or driving force can be generated directly, without intermediate interlocking parts, no friction, no noise, no rotor fever, without centrifugal force and other issues. Therefore, its application will be more extensive. Linear Synchronous Motor because of superior performance, applications is the same as the linear induction motor, a substituted trend. Linear stepper motor is used in CNC plotter, recorder, digital control chart machine, CNC cutting machine, disk storage, precision positioning mechanism and other equipment.


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