![]() ![]() The rotor current due to these emf lags by nearly 90° owing to low 'R' and high 'X' of the rotor winding. The generated rotor emf vary in phase with the stator current and flux. The direction of the emf is determined by fleming's right-hand rule, will be outward on one side of the vertical axis and inward on the other side of the vertical axis as indicated by the dots and crosses as shown in the below figure. ![]() Motor at Running : When, however, the rotor is made to rotate say in the clockwise direction by some external means, the rotor conductors cut across the stator field, causing an emf to be generated in them. The two sets of forces will cancel and the rotor will experience no torque. The forces on the rotor conductors in the top half are in a downward direction, whereas the forces on the rotor conductors in the bottom half are in the upward direction. The behaviour can readily be understood by means of the following example. The axis of the stator and rotor fields are aligned. The operation of a 3-phase induction motor is based upon the application of Faraday Law and the Lorentz force on a conductor. The rotor currents establish poles on the rotor surface and these are in direct line (along the horizontal axis) with the stator poles. The directions of currents in the rotor conductors are also shown. ![]()
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