Linear Induction Motor
A Linear Induction Motor is a non-contacting, high speed, linear motor that operates on the same principal as a rotary, squirrel cage, Induction Motor. It is produced linear motion instead of rotary motion as in a induction motor.
In Linear Induction Motor stator known as primary and rotor known as secondary.
When three phase supply is connected to the primary of Linear Induction Motor. hence, traveling flux wave is produced. this flux wave travel along the length of primary part of Linear Induction Motor and induced an EMF in the secondary.current is circulate in secondary because of this EMF. traveling wave is interact with induced current by that EMF and it will be produced translational force.If one part is moving and other is fixed,then force is produced on the moving part(primary or secondary).
- If primary is fixed, force will produced on the secondary part and it will be move in same direction of traveling wave.
- If secondary is fixed, force will produced on the primary part and it will be move in opposite direction of traveling wave.
figure shows the traction locomotive using linear induction motor. This system has secondary is fixed and primary is movable.
Lets consider, linear induction motor for traction locomotive system.
By using pantograph single phase supply is collected from overhead conductor. this single phase supply is given to the converter which is convert single phase in to three phase. three phase primary winding is used, three phase supply is given to that three phase primary winding. Traveling flux is induced, because of three phase primary winding and that flux is linked with the secondary part and induced EMF in secondary. So that EMF is circulate the current in the secondary which is interacts with the traveling flux of primary and it will produced force on the moving part. here, secondary is fixed and primary is movable. therefore, locomotive is run, because of produced forced is acting on locomotive.
the synchronous speed of Linear IM is given by,
Vs = 2 τ f meter/sec
where, f = frequency
τ = pole pitch
Application Linear Induction Motor:-
- traction locomotive system.
- pulling machine.
- electromagnetic pump.
- high speed vehicle .
- door sliding purpose .
Advantages Linear Induction Motor:-
- No limitation to obtain maximum speed.
- Rotation of parts avoided, so mechanical loss is less.
- initial cost is low.
- maintenance is less.
- Its power to weight ratio is batter, then the rotary IM.
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