ANALYSIS OF CHARACTERSTICS OF 3-PHASE INDUCTION MOTOR
1.
INTRODUCTION:
v A 3-phase induction motor consists of
a stator and rotor.
v The stator carries a 3-phase winding
(called stator winding) while the rotor carries a short circuited winding
(called rotor winding).
v Only the stator winding is fed from
3-phase supply.
vThe rotor winding derives its voltage
and power from the externally energized stator winding through electromagnetic
induction.
2. COMPONENTS OF INDUCTION MOTOR:
1.) Rotor..
v The rotor, mounted on a shaft,
is a hollow laminated core having slots on its outer periphery.
v The winding placed in these
slots (called rotor winding) may be one of the following two type :
¡
(i) Squirrel
cage type
¡
(ii) Wound
type
2.)Stator..
v
It consists of a steel frame
which encloses a hollow, cylindrical core made up of thin laminations of silicon
steel to reduce hysteresis and eddy current loss.
v
A number of evenly spaced slots
are provided on the inner periphery of the laminations.
v
The insulated conductors are
placed in the stator slots and are suitably connected to form a balanced
3-phase star or delta connected circuit.
3. WORKING OF INDUCTION MOTOR:
v
When the stator windings are connected to a three-phase power
supply and rotor circuit is closed, the induced voltage in the rotor windings
produce rotor currents that interact with the air gap field to produce torque.
v
Rotor, if free to do so, will start rotating.
v
This field is such that its
poles do not remain in a fixed position on the stator but go on shifting their
positions around the stator.
4. THE VARIOUS METHODS OF SPEED CONTROL OF
3-PHASE INDUCTION MOTOR:
v Pole Changing
v Variable Supply Frequency
v Variable rotor resistance control
v Variable supply voltage control
5. ADVANTAGES OF 3-PHASE INDUCTION MOTOR:
v It has simple and rugged construction.
v It is relatively cheap.
v It requires little maintenance.
v It has high efficiency and reasonably good power
factor.
v It has self-starting torque.
v In fractional-horsepower (less than 1hp) applications,
the single-phase motor will be less efficient.
6. BLOCK DIAGRAM in SIMULINK:
7. BLOCK PARAMETERS:
8. MATLAB-SIMULINK
ANALYSIS:
ØROTOR
SPEED(rad./sec.) and ELECTROMAGNETIC TORQUE(N*m)
§ @(415V
,50 Hz )3-phase Voltage Supply
ØSTATOR
CURRENT(A) and ROTOR CURRENT(A)
§ @(415V
,50 Hz )3-phase Voltage Supply
ØSTATOR
CURRENT(A) and ROTOR CURRENT(A)
§ @(415V
,60 Hz )3-phase Voltage Supply
Ø ROTOR
SPEED(rad./sec.) and ELECTROMAGNETIC TORQUE(N*m)
§ @(415V
,60 Hz )3-phase Voltage Supply
