Protection of Meters
RC Coupled Amplifier
Construction of Three Phase Induction Motor
Classification of Squirrel Cage Induction Motor
Deep Bar Double Cage Induction Motor
Starting Methods for Polyphase Induction Machine
Speed Control of Three Phase Induction Motor
Crawling and Cogging of Induction Motor
Speed Control of Induction Motor Using Static Devices
Schrage Motor Operation Principle and Characteristics of Schrage Motor
Phasor Diagram for AC Series Motor
Linear Induction Motor
Inverted or Rotor Fed Induction Motor
Induction Motor | Working Principle | Types of Induction Motor
Working Principle of Three Phase Induction Motor
Types of Three Phase Induction Motor
Torque Equation of Three Phase Induction Motor
Single Phase Induction Motor
Types of Single Phase Induction Motor | Split Phase Capacitor Start Run Shaded Pole
Equivalent Circuit for an Induction Motor
Losses and Efficiency of Induction Motor
Torque Slip Characteristics of Induction Motor
Testing of Induction Motor
Blocked Rotor Test of Induction Motor
No Load Test of Induction Motor
Circle Diagram of Induction Motor
Linear Induction Motor
Construction of a Linear Induction MotorConstruction wise a LIM is similar to three phase induction motor in more ways than one as it has been depicted in the figure below. In LIM stator and rotor are called primary and secondary respectively. If the stator of the poly phase induction motor shown in the figure is cut along the section aob 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.
There is another variant of LIM also being used for increasing efficiency known as the double sided linear induction motor or DLIM, as shown in the figure below. Which has a primary winding on either side of the secondary, for more effective utilization of the induced flux from both sides.
Working of a Linear Induction MotorWhen the 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, which will travel along the entire length of the primary. Electric current is induced into the aluminum conductors or 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. When supply is given, the synchronous speed of the field is given by the equation :
The developed field will results in a linear traveling field, the velocity of which is given by the equation,
Application of Linear Induction MotorA linear induction motor is not that widespread compared to a conventional motor, taking its economic aspects and versatility of usage into consideration. But there are quite a few instances where the LIM is indeed necessary for some specialized operations.
Few of the applications of a LIM have been listed below.
- Automatic sliding doors in electric trains.
- Mechanical handling equipment, such as propulsion of a train of tubs along a certain route.
- Metallic conveyor belts.
- Pumping of liquid metal, material handling in cranes, etc.