synchronous speed
induction motor never runs at synchronous speed, if it does so there would not be any relative speed between stator flux and rotor and no emf will induce in rotor and we can not apply motor principle as we need current carrying conductor in magnetic field.
Stator is part of rotating mechanical device thats sorrounds the rotor to rotate it through the induced magnetic field while the Rotor, is the one who is rotated by produced magnetic field in the stator,.
In induction motors no seprate source is required to start the motor,and motor itself induces emf as the word induction clearly reflects it starting principle while in case of synchronous motors ,motor is synchronised with an external source of emf.
if the relative speed of magnetic flux of stator and rotor becomes zero there will be no back emf and eventually the rotor gets zero speed
The induction motor is the special kind of motor which runs below and above the synchronous speed. which the synchronous motor runs nearly equal the synchronous speed. The operation of synchronous motor runs with dc field excited hence separate dc field current is given to the field circuit. where as the induction motor the field and main field is drawn from the same supply hence no excitation is required. But due to this separate starting mechanism has to be required in case of the single phase induction motor.
Slip is referred to as the difference between the speed of the rotor and the speed of the rotating magnetic field in the stator of the induction motor. Speed of the rotor=n(1-s) Speed of the rotating magnetic field= f/p
induction motor never runs at synchronous speed, if it does so there would not be any relative speed between stator flux and rotor and no emf will induce in rotor and we can not apply motor principle as we need current carrying conductor in magnetic field.
The shaft of an AC induction motor rotates because of the torque created by the interaction between the magnetic field of the stator and the magnetic field of the rotor.
A three-phase motor has a steady rotating magnetic field generated by the stator coil, and the rotor just follows the field.
When three phase supply is given to the three phase stator winding of the induction motor,a rotating magnetic field is developed around the stator which rotates at synchronous speed.This rotating magnetic field passes through the air gap and cuts the rotor conductors which were stationary.Due to the relative speed between the stationary rotor conductors and the rotating magnetic field,an emf is induced in the rotor conductors.As the rotor conductors are short circuited, current starts flowing through it.And as these current carrying rotor conductors are placed in the magnetic field produced by the stator, they experiences a mechanical force i.e. torque which moves the rotor in the same direction as that of the rotating magnetic field. the induction motor can't run at the synchronous speed because at synchronous speed the induction motor can not develop any torque to move the rotor from its stationary position.
We know that relative speed is responsible to induce voltage. If rotor and the rotating field (stator) speed is same, no voltage will induced because relative speed will be zero. For IM relative speed is not zero and it does not move with sync. speed, and so it is called asynchronous motor.
A starter is unnecessary because the stator produces a rotating magnetic field.
Stator is part of rotating mechanical device thats sorrounds the rotor to rotate it through the induced magnetic field while the Rotor, is the one who is rotated by produced magnetic field in the stator,.
In an induction motor the rotor currents are induced by the magnetic field of the stator, and if the motor were to run at synchronous speed the induced currents and also the torque would fall to zero. The rotor currents alternate at a low frequency determined by the 'slip', which is the percentage amount that the rotor speed is below the synchronous speed. The output torque is proportional to the slip at near-synchronous speeds.
calculate the synchronous speed from the frequency & the no. of magnetic poles in the stator, then measure the actual speed of it with a tachometer, then subtract the actual speed from the synchronous speed.
if the relative speed of magnetic flux of stator and rotor becomes zero there will be no back emf and eventually the rotor gets zero speed
In induction motors no seprate source is required to start the motor,and motor itself induces emf as the word induction clearly reflects it starting principle while in case of synchronous motors ,motor is synchronised with an external source of emf.