List of Figures iv
List of Symbols
1 Introduction 1
2 Review of Literature
2.1 Linear Induction Motor 2
2.2 Double layer Winding
2.3 Electro-magnetic Bearings 6
3 Work Progress 9
The main idea behind this project is to understand the designing and operation of a Linear Levitating Machine and be able to create a successful prototype using the knowledge that we have acquired.
Through this project we want to design and develop a machine which is capable of moving with the help of electromagnetic forces produced by the poles made by the stator windings and is lifted up due to the force ...view middle of the document...
Again, in contrast with its rotary country part, an LIM may have a moving primary (with a fixed secondary), or a moving secondary (the primary being stationary).
The simplest form of construction of a linear Motor is like a three phase induction motor. It has three phase windings housed in slots in a field system. It is simply the primary winding on a stator in case of an induction motor from middle.
A flat or single-sided LIM i.e., a SLIM, is obtained by the imaginary process of “cutting” and “unrolling” a rotary induction motor as shown in figure. In practice, the primary or stator of a LIM consists of a rectangular slotted structure formed by a stack of steel laminations. Within the slots of the primary stack are laid the poly phase windings to produce the linearly travelling magnetic field, just like the rotating magnetic field in a rotary induction motor, produced by the poly phase stator windings. The secondary of the LIM, or rotor which is an aluminium sheet (or copper), with or without a solid back iron plate, completes the magnetic circuit and creates the magnetic flux linkage across the air gap. This in turn induces a voltage on the conductive wall, which generates an eddy current in the conducting outer layer of the secondary. The interaction between the eddy current and the changing electromagnetic field generates electromagnetic thrust on the plate in the longitudinal direction of the motor.
1. Short primary linear induction motor
2. Short secondary linear induction motor
When the primary is excited by a balanced three phase supply, a rotating electro-magnetic flux is induced in primary. The synchronous speed of the field is given by the equation:
NS = 2fs /p
Here fs is supply frequency (Hz), p is the number of poles, Ns is the synchronous speed of the rotation of magnetic field in revolutions per second.
The developed field will results in a linear travelling field, the velocity of which is given by the equation vs = 2*t*fs m/s. here vs is velocity of linear travelling field, t is the pole pitch. For a slip of s, the speed of conducting slave in a linear motor is given by vr = (1-s)*vs
Linear Motors have found a number of applications. Some of the most commonly used ones are listed below:
a. Automatic sliding doors in an electrical train,
b. Metallic belt conveyer,
c. Mechanical handling equipment, such as propulsion of a train of tubs along a certain route,
d. Shuttle- propelling application.
e. High and medium speed applications have been tried with linear motor propulsion of vehicles with air cushion or magnetic suspension.
f. High speed application as a travelling crane motor where the field system is suspended from hoist.
2.2 DOUBLE LAYER WINDING
The armatures of nearly all synchronous generators and motors, and most induction motors are wound with double-layer windings. In a double layer winding,...