Linear Induction Motor

Linear Induction Motor

Linear Induction Motor Rotary, squirrel cage induction motor, split radially along its axis of rotation and flatten out is a linear induction motor that produces direct linear force instead of torque

Linear Induction Motor 

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non-contacting, high speed, linear motor that operates on the same principle as a rotary, squirrel cage, induction motor. capable of speeds up to 1800 in/sec [45 m/s] used in applications where accurate positioning is not required.

Construction primary 

coil assembly and secondary (reaction plate )

Forces Produced

Forces Produced 

LEM’s develop two mutually perpendicular forces, one in the direction of motion and the other normal to the direction of motion.

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The normal force may be an attraction or a repulsion force between the primary and secondary. A machine in which the net force is such that the secondary tends to be suspended over the primary may be used mainly for suspension and called a linear levitation machine (LLM).

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Conversely, a machine used primarily for producing thrust is called a linear motor

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Both LIM’s and LSM’s may be used a levitation or

Operation 

A variable frequency inverter will provide velocity control of a linear induction motor.

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A Linear Induction Motor (LIM) equipped with a linear encoder point to point programmable positioning

Advantages Rotary vs. Linear Motors

Linear Motor Direct thrust Minimal maintenance No internal moving parts Virtually silent operation Very low inertia Higher Cost Less Common

Rotary/Linear Conversion Rotary to linear mechanism required More maintenance More wear Noisy Higher inertia Low Cost Widely Used

Advantages 

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Small, compact – fits into smaller spaces No backlash from gears or slippage from belts – provides smooth operation Reliability – non-contact operation reduces component wear and reduces maintenance Wide speed range Designs are available with either a moving coil or moving magnets.

Limitations 

Costly to purchase and install

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Force Per Package Size: Linear motors are not compact force generators compared to a rotary motor.

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Heating: The forcer is often attached to the load. If an application is sensitive to heat, thermal management techniques need to be applied.

Applications 

Linear applications (lower precision)

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Conveying Systems Cranes Drives Baggage Handling Personal Rapid Transport Systems Theme Park Rides

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On-the-Fly Welder

Appllications 

On-the-Fly Welder

The controller receives velocity and position data from an incremental encoder mounted to a roller on the conveyor belt. The secondary motor/drive system receives instructions from the controller, based on a ratio of the velocity and position information supplied by the primary system encoder. The linear motor forcer carries the weld head and is mounted on an overhead platform in line with the conveyor. .

Applications 

Capsule Filling Machine

Linear Motor • A few countries are using powerful electromagnets to develop high-speed trains, called maglev trains. • Maglev is short for magnetic levitation, which means that these trains will float over a guide way using the basic principles of magnets.

•The principle of a Magnet train is that floats on a magnetic field and is propelled by a linear induction motor. A maglev train floats about 10mm above the guidway on a magnetic field. It is propelled by the guidway itself rather than an onboard engine by changing magnetic fields.

Basic Operation ••Wheels - Supports and guides until levitation occurs Top Halbach Arrays - Levitation •Side Halbach Arrays - Guidance •Bottom Halbach Arrays - Stability for sharp turns

Stopped/Low Velocities

Fast Velocities