PowerPoint Presentation
Induction Motors
2Three-Phase Induction MotorInduction motors are used worldwide
in many residential, commercial, industries.Induction Motors
transform electrical energy into mechanical energy. The three phase
induction motor is the most widely used electrical motor. Almost
80% of the mechanical power used by industries is provided by three
phase induction motors because of its simple and rugged
construction, low cost, good operating characteristics, good speed
regulation. In three phase induction motor the power is transferred
from stator to rotor winding through induction. The Induction motor
is also called asynchronous motor.3Induction Motor Components
Stator: 1) Consist of No of stamping which are slotted for
receiving the stator winding.2) Stator carries the 3 Phase winding
is fed from 3 phase supply3) Stator is wound for Fixed No of poles.
No of poles is decided by the requirement of speed.4) Stator
carries the field windings and when fed from 3 phase AC supply,It
produces REVOLVING MAGNETIC FLUX of constant magnitude and rotates
at speed called as Syncronous speed Ns
2) Rotor:
Rotor:There are two types of the rotorSquirrel cage RotorPhase
wound rotor/wound rotor/slip ring rotor.Depending upon the type of
rotor construction used the three phase induction motor are
classified as:Squirrel cage induction motor,Slip ring induction
motor or wound induction motor or phase wound induction motor.
5Squirrel Cage RotorSquirrel cage rotor is most widely used
rotor because its simple and robust construction.It consist of
cylindrical laminated core with parallel slots for carrying rotor
conductors.Conductors are heavy bar of Copper, aluminum or
alloy.Bars are inserted from one end for semi-closed slots.Theses
bars are brazed or electrically welded or bolted to Two Heavy and
stout end rings.Thus giving Cage Type of construction.
Squirrel Cage Rotor
Advantages of squirrel cage induction rotor-Its construction is
very simple and rugged.As there are no brushes and slip ring, these
motors requires less maintenance.Applications: Squirrel cage
induction motor is used in lathes, drilling machine, fan, blower
printing machines etc 8Wound rotor IM
A wound rotor has a 3-phase , Double layer , distributed winding
consist of the coil.It is wound for same No of poles as the stator
pole.It is wound for 3 phase (Always)The rotor winding starred
internally.Other terminals are connected to three slip rings which
turn with the rotor. The slip rings/brushes allow external
resistors to be connected in series with the winding.
9Slip ring RotorAdvantages of slip ring induction motor 1)It has
high starting torque and low starting current.2) Possibility of
adding additional resistance to control speed.
Application: Slip ring induction motor are used where high
starting torque is required i.e in hoists, cranes, elevator
etc.
Construction
Squirrel cage rotorWound rotorNotice the slip
ringsConstruction
Cutaway in a typical wound-rotor IM. Notice the brushes and the
slip ringsBrushesSlip rings12Nameplate
