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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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