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Linear induction motor

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Linear induction motor

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Linear induction motor

  1. 1. LINEAR INDUCTION MOTOR By Prof. Abhishek Gedam
  2. 2. WHAT ARE LINEAR MOTORS?  Linear motors are electric induction motors that produce motion in a straight line rather than rotational motion.  In a traditional electric motor, the rotor (rotating part) spins inside the stator (static part)  In a linear motor, the stator is unwrapped and laid out flat and the "rotor" moves past it in a straight line.
  3. 3. CONSTRUCTION OF A LINEAR INDUCTION MOTOR  If the stator of the poly phase induction motor is cut along the section and laid on a flat surface, then it forms the primary of the LIM housing the field system, and consequently the rotor forms the secondary consisting of flat aluminum conductors with ferromagnetic core for effective flux linkage.
  4. 4. WORKING OF A LINEAR INDUCTION MOTOR  Primary of an LIM is excited by a balanced three phase power supply  A traveling flux is induced in the primary instead of rotating 3 φ flux  Electric current is induced into the secondary due to the relative motion between the traveling flux and the conductors  This induced current interacts with the traveling flux wave to produce linear force or thrust F.  If the secondary is fixed and the primary is free to move, the force will move the primary in the direction of the force, resulting in the required rectilinear motion.
  5. 5. SPEED  Synchronous speed of the field 𝒏 𝒔 = 𝟐𝒇 𝒔 𝒑  Where, fs = supply frequency in Hz, p = number of poles
  6. 6.  The developed field will results in a linear traveling field  The velocity of which is given by the equation Vs=2tfs Vs = velocity of the linear traveling field, t = pole pitch For a slip of s, the speed of the LIM is given by Vr=(1-s)vs
  7. 7. ADVANTAGES  There are no moving parts to go wrong  As the platform rides above the track on a cushion of air, there is no loss of energy to friction or vibration  As both acceleration and braking are achieved through electromagnetism, linear motors are much quieter than ordinary motors. DISADVANTAGES Because the air-gap is greater  more power is required  efficiency is lower
  8. 8. APPLICATION OF LINEAR INDUCTION MOTOR  Automatic sliding doors in electric trains.  Mechanical handling equipment, such as propulsion of a train of tubs along a certain route.  Metallic conveyor belts.

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