l35 3ph im

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Post on 13-Sep-2014

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  • Converts electrical power into mechanical powerEnergy transfer by means of electromagnetic inductionIndustrial & Commercial Applications Pumping Systems Refrigeration Systems Compressors Fans & Blowers Industrial Drives

  • Rotating Magnetic Field3 phase supply is given to a balanced 3 phase winding.3 alternating magnetic fluxes displaced mutually at 120o is produced.

  • Considering different instances of time:(i) At wt = 0oThe instantaneous fluxes are

    The resultant magnetic flux is 1.5 times peak value and Acting at 90o to axis of reference.

  • (ii) At wt = 60oThe instantaneous fluxes are

    The resultant magnetic flux is 1.5 times peak value and actingat 30o to axis of reference. i.e., rotated by 60o w.r.t. previous angle

  • Similarly if various instances are considered upto 360o, it is seen that the resultant always has a magnitude of 1.5 times peak value and pointing in a direction at the angle of consideration.For every 360o, the resultant magnetic field completes one rotation.Inference:When 3 phase currents flow in a balanced 3 phase winding, a rotating magnetic field is created which has constant magnitude, but rotates in synchronism with supply frequency.

    This speed of rotating magnetic field is called SYNCHRONOUS SPEED

  • Construction Squirrel Cage, Slip Ring Connection Stator : Star, Delta Rotor : Cage, Wound Application Constant Power, Constant Torque, Constant Speed, Variable Torque - Variable Speed

  • Stator frame: Cast Iron, Mechanical Support to stator core Stator core: Stack of cylindrical steel laminations Stator Slots: Inner periphery, Windings

  • Types on the basis of rotor construction Squirrel Cage Rotor Slip Ring Rotor Cylindrical Laminated core Slots cutout on outer periphery Conductors placed in slots

  • Skewed arrangement Copper or Aluminum Bars Conductors shorted by end rings Closed rotor circuit

  • One end of Rotor conductors connected to each other (Star)External resistance Other ends connected to slip rings Slip rings in contact with brushes Brushes connected to external resistance

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