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    Induction

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    adarsh
    The document summarizes the construction and operation of 3-phase induction motors. It describes the key components of the stator and rotor, including squirrel cage and wound rotor designs. It explains that the stator generates a rotating magnetic field from AC current that induces current in the rotor, producing torque. It notes that the rotor must operate slightly slower than synchronous speed in order to generate this induced current.

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    Induction

    Uploaded by

    adarsh
    105 views5 pages
    The document summarizes the construction and operation of 3-phase induction motors. It describes the key components of the stator and rotor, including squirrel cage and wound rotor designs. It explains that the stator generates a rotating magnetic field from AC current that induces current in the rotor, producing torque. It notes that the rotor must operate slightly slower than synchronous speed in order to generate this induced current.

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    The document summarizes the construction and operation of 3-phase induction motors. It describes the key components of the stator and rotor, including squirrel cage and wound rotor designs. It explains that the stator generates a rotating magnetic field from AC current that induces current in the rotor, producing torque. It notes that the rotor must operate slightly slower than synchronous speed in order to generate this induced current.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    105 views5 pages

    Induction

    Uploaded by

    adarsh
    The document summarizes the construction and operation of 3-phase induction motors. It describes the key components of the stator and rotor, including squirrel cage and wound rotor designs. It explains that the stator generates a rotating magnetic field from AC current that induces current in the rotor, producing torque. It notes that the rotor must operate slightly slower than synchronous speed in order to generate this induced current.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    of 5

    1.

    INDUCTION MOTORS
    OBJECTIVE -
    1. Construction, types and principle of operation of 3-phase induction motors.
    2. Equivalent circuit of 3-phase induction motor. 3. Different
    types of starters like auto-transformer starter, star-delta starter.
    4. Principle of operation of single phase induction motor
    CONSTRUCTION -
    A typical motor consists of two parts namely stator and rotor like other type of
    motors. 1. An outside stationary stator having coils supplied with AC current to
    produce a rotating magnetic field, 2. An inside rotor attached to the output
    shaft that is given a torque by the rotating field.
    STATOR -

    ROTOR –
    Squirrel cage rotor – In the squirrel-cage rotor, the rotor winding consists of
    single copper or aluminium bars placed in the slots and short-circuited by end-
    rings on both sides of the rotor. Most of single phase induction motors have
    Squirrel-Cage rotor. One or 2 fans are attached to the shaft in the sides of rotor
    to cool the circuit.
    Wound Rotor -In the wound rotor, an insulated 3-phase winding similar to the
    stator winding wound for the same number of poles as stator, is placed in the
    rotor slots. The ends of the star-connected rotor winding are brought to three
    slip rings on the shaft so that a connection can be made to it for starting or
    speed control. It is usually for large 3 phase induction motors. Rotor has a
    winding the same as stator and the end of each phase is connected to a slip
    ring. Compared to squirrel cage rotors, wound rotor motors are expensive
    and require maintenance of the slip rings and brushes, so it is not so common
    in industrial application
    Name plate of 3 phase induction motor-

    PRINCIPLE OF OPERATION -
    An AC current is applied in the stator armature which generates a flux in the
    stator magnetic circuit. This flux induces an emf in the conducting bars of
    rotor as they are “cut” by the flux while the magnet is being moved (E = BVL
    (Faraday’s Law)) A current flows in the rotor circuit due to the induced emf,
    which in term produces a force, (F = BIL) can be changed to the torque

    MOTOR SLIP

    The rotor in an induction motor can not turn at the synchronous speed. In
    order to induce an EMF in the rotor, the rotor must move slower than the SS.
    If the rotor were to somehow turn at SS, the EMF could not be induced in the
    rotor and therefore the rotor would stop. However, if the rotor stopped or
    even if it slowed significantly, an EMF would once again be induced in the rotor
    bars and it would begin rotating at a speed less than the SS.

    The relationship between the rotor speed and the SS is called the Slip.
    Typically, the Slip is expressed as a percentage of the SS. The equation for the
    motor Slip is:
    % S = (SS – RS)/SS X100
    Where:
    %S = Percent Slip SS = Synchronous Speed (RPM) RS = Rotor Speed (RPM)

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