linear induction motor for high speed application especially in traction application to make speed to max value .its operation is almost similar to poly induction motor

1. Presented by
K. SrinivasGuide
Naveen reddy sir
uma Mahesh rao sir

3. Contents:
 What is a machine and a motor?
 Types of motors
 Introduction to induction motor & basic operation of motor
 What is liner motion &linear induction motor
 Construction of linear induction motor
 Types of linear induction motor
 Impact of rotor resistance
 Control mechanism for the change material of rotor winding
 characteristic‘s & different mathematical eq’s
 Applications in real world & in development of country
 Pons & cons
 Conclusion

4. Machine: An apparatus using mechanical power and having several parts each with a
definite function and together performing a particular task.
Extending to electrical machines which comes under an equipment which converts
electrical to mechanical energy and vice versa.
Motor: A motor is an electrical machine that converts electrical to mechanical energy.

5. Is both machine and device are
similar?

6. Types of electrical motors:

7. What is a Induction Motor:
Which converts the electrical to mechanical energy.
Principle:
Based on the FARADAY’S LAWS OF INDUCTION, electromagnetic field i.e.,
emf is induced at slip frequency on rotor side. Hence it is named as INDUCTION
MOTOR.
It is a self starting machine, since the rotating magnetic field is produced
when the supply is given to stator side. This approach is visualized in polyphase
induction motor.

8. Linear Motion:
Linear motion (also called rectilinear motion) is a motion along a straight line,
and can therefore be described mathematically using only one spatial dimension. ...
In general motion, a particle's position and velocity are described by vectors,
which have a magnitude and direction.
If a motor exhibits the above phenomenon then the motor posses the property
LINEAR MOTION.
Linear Motor:
Amotor that produces thrust in a straight line by direct induction rather than
with the use of gears called also Linear induction motor.

9. Linear vs Rotating:
• Linear motion involves an object moving from one point to another in a
straight line.
• Rotational motion involves an object rotating about an axis.

10. Construction:
Linear Induction motor abbreviated as LIM, is basically a special purpose motor
that is in use to achieve rectilinear motion rather than rotational motion as in the
case of conventional motors.
When it comes to construction point of view it is almost similar to Polyphase
induction motor.
A typical air gap in LIM is of order 25mm while in a cylindrical motor it is
about 1mm.

11. 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 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 aluminium 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.

12. Principle of Operation:
When 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
aluminium 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.

13. When supply is given, the synchronous speed of the field is given by the equation :
Where, fs is supply frequency in Hz, and
p = 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 traveling field, the velocity of which is
given by the equation,
where, vs is velocity of the linear traveling field, and t is the pole pitch. For a slip
of s, the speed of the LIM is given by

14. Types of linear induction motor
Iron Core
Coils wound around teeth
of laminations on forcer
Ironless Core
Dual back iron separated by
spacer
Coils held together
with epoxy
Slotless
Coil and back iron held
together with epoxy

15. Iron PlateRare earth magnets
Laminated forcer
assembly and mounting
plate
Coil wound Around
Forcer lamination
Hall effect
and thermal
sensors
Iron Core
Distinguishing Feature
Copper windings around forcer laminations over a single magnet
rail
Pros:
 Highest force available per unit volume
 Efficient Cooling
 Lower cost
Cons:
X High attractive force between forcer & magnet track
X Cogging: iron forcer affects thrust
force as it passes over each
magnet (aka velocity ripple)

16. Distinguishing Feature
Forcer constructed of wound coils held
together with epoxy and running
between two rails (North and South)
Also known as “Aircore” or “U-
channel” motors
Merits:
 No attractive forces in forcer
 No Cogging
 Low weight forcer - No iron means
higher accel/decel rates
Top View
Forcer
Mounting
Plate
Rare
Earth
Magnets
Horseshoe
Shaped
backiron
Winding, held
by epoxy
Hall Effect and
Thermal
Sensors in coil
Front View
Ironless
Demerits:
X Low force per package size
X Lower Stiffness; limited max load without improved structure
X Poor heat dissipation
X Higher cost (2x Magnets!)

17. Distinguishing Feature
Mix of ironless and iron core: coils with
back iron contained within aluminum
housing over a single magnet rail
Advantages over ironless:
 Lower cost (1x magnets)
 Better heat dissipation
 Structurally stronger forcer
 More force per package size
Advantages over iron core:
 Lighter weight and lower inertia forcer
 Lower attractive forces
 Less cogging
Side View
Front View
Back
iron
Mounting
plate
Coil
assemblyThermal
sensor
Rare
Earth
Magnets
Iron
plate
Slotless

18. Disadvantages
X Some attractive force and cogging
X Less efficient than iron core and
ironless - more heat to do the same
job
Side View
Front View
Back
iron
Mounting
plate
Coil
assemblyThermal
sensor
Rare
Earth
Magnets
Iron
plate
Slotless

19. Change of rotor resistance:
Electrical voltage get effected due to resistance of the material which we
use for conduction. In extension to this the rotor secondary resistance is
changed based on the type of the material we use.
Here the rotor resistance differs when primary moves in different areas.

20. Characteristics of LIM:
Different forces in LIM
1. Thrust Force
2. Lateral Force
3. Normal Force

21. Thrust Force which is developed is directly proportional to the square of the
applied voltage and this reduces as the slip value is reducing similar to that of a
induction motor with high rotor resistance.

22. Shape of the magnetic field created by 2pole ,3phase
linear stator over one cycle

23. Applications
Small Linear Motors
 Packaging and Material Handling
 Automated Assembly
 Reciprocating compressors and
alternators
Large Linear Induction Machines
(3 phase)
 Transportation
 Materials handling
 Extrusion presses

26. Pros
1. Direct electromagnetic force (no mechanical elements, no limitations for speed).
2. Economical and cheap maintenance
3. Easy expansion for any linear motion of system topology.
4. Exact positioning in closed loop systems.
5. Possibility to provide inductor and windings separate cooling.
Cons
1)Power factor and efficiency are less than of rotary motors because of a ratio of large
air gap between inductors and pole pitch
2)The longitudinal end effect reduces power factor and efficiency. This can be noticed
only with fast speed and small pole number motors. Influence of the longitudinal end
effect can be reduced with special motor design methods.
3) Extra vibrations with distortions can be noticed because of uncompensated normal
force

27. Conclusion
From above scenario it is clear that
introduction of linearity in the motion of
induction motor makes the equal, linear
development in the country & its technology