Insulation Resistance Measurement
Ampere's Circuital Law
Mechanical Equivalent of Heat
Trees and Cotrees
IntegratorClosely Related Articles
3 Phase 1M
Types of 3 Phase IM
Torque in 3 Phase IM
Single Phase Induction Motor
Types of 1 Phase 1M
Equivalent Circuit of IM
Efficiency of Induction Motor
Testing of Induction Motor
Blocked Rotor Test of IM
No Load Test of Induction Motor
Circle Diagram of Induction Motor
Construction of 3 Phase IM
Squirrel Cage Induction Motor
Deep Bar IM
Starting Methods for Polyphase IM
Speed Control of 3 Phase IM
Crawling Cogging of IM
Speed Control of Induction Motor
Phasor Diagram for AC Series Motor
Linear Induction Motor
Rotor Fed Induction Motor
Working Principle of Three Phase Induction Motor
Rotor: Rotor of three phase induction motor consists of cylindrical laminated core with parallel slots that can carry conductors. Conductors are heavy copper or aluminum bars which fits in each slots & they are short circuited by the end rings. The slots are not exactly made parallel to the axis of the shaft but are slotted a little skewed because this arrangement reduces magnetic humming noise & can avoid stalling of motor.
Working of Three Phase Induction Motor
Production of Rotating Magnetic FieldThe stator of the motor consists of overlapping winding offset by an electrical angle of 120°. When the primary winding or the stator is connected to a 3 phase AC source, it establishes a rotating magnetic field which rotates at the synchronous speed. Secrets Behind the Rotation: According to Faraday’s law
an emf induced in any circuit is due to the rate of change of magnetic flux linkage through the circuit. As the rotor winding in an induction motor are either closed through an external resistance or directly shorted by end ring, and cut the stator rotating magnetic field, an emf is induced in the rotor copper bar and due to this emf a current flows through the rotor conductor. Here the relative speed between the rotating flux and static rotor conductor is the cause of current generation; hence as per Lenz's law the rotor will rotate in the same direction to reduce the cause i.e. the relative velocity.
Thus from the working principle of three phase induction motor it may observed that the rotor speed should not reach the synchronous speed produced by the stator. If the speeds equals, there would be no such relative speed, so no emf induced in the rotor, and no current would be flowing, and therefore no torque would be generated. Consequently the rotor can not reach the synchronous speed. The difference between the stator (synchronous speed) and rotor speeds is called the slip. The rotation of the magnetic field in an induction motor has the advantage that no electrical connections need to be made to the rotor. Thus the three phase induction motor is:
- Less armature reaction and brush sparking because of the absence of commutators and brushes that may cause sparks.
- Robust in construction.
- Easier to maintain.
Working Principle of Three Phase Induction Motor - Video
Closely Related Articles Induction Motor | Working Principle | Types of Induction MotorTypes of Three Phase Induction MotorTorque Equation of Three Phase Induction MotorSingle Phase Induction MotorTypes of Single Phase Induction Motor | Split Phase Capacitor Start Run Shaded PoleEquivalent Circuit for an Induction MotorLosses and Efficiency of Induction MotorTorque Slip Characteristics of Induction MotorTesting of Induction MotorBlocked Rotor Test of Induction MotorNo Load Test of Induction MotorCircle Diagram of Induction MotorMore Related Articles Construction of Three Phase Induction MotorClassification of Squirrel Cage Induction MotorDeep Bar Double Cage Induction MotorStarting Methods for Polyphase Induction MachineSpeed Control of Three Phase Induction MotorCrawling and Cogging of Induction MotorSpeed Control of Induction Motor Using Static DevicesSchrage Motor Operation Principle and Characteristics of Schrage MotorPhasor Diagram for AC Series MotorLinear Induction MotorInverted or Rotor Fed Induction MotorNew Articles Measurement of Insulation ResistanceAmpere's Circuital LawMechanical Equivalent of HeatTrees and Cotrees of Electric NetworkDifferentiatorIntegrator