How voltage is induced in the rotor of an induction motor?
Operating principle. In a three-phase induction machine, alternating current supplied to the stator windings energizes it to create a rotating magnetic flux. The flux generates a magnetic field in the air gap between the stator and the rotor and induces a voltage which produces current through the rotor bars.
What does the rotor do in an induction motor?
The rotor is located inside the stator and is mounted on the AC motor’s shaft. The term “rotor” is derived from the word rotating. The rotor then is the rotating part of the AC motor. The objective of these motor components is to make the rotor rotate which in turn will rotate the motor shaft.
What is induced emf in induction motor?
The conductors of the rotor are stationary. This stationary conductor cut the rotating magnetic field of the stator, and because of the electromagnetic induction, the EMF induces in the rotor. This EMF is known as the rotor induced EMF, and it is because of the electromagnetic induction phenomenon.
Why an EMF is induced at the rotor side of a three-phase induction motor?
Injecting Slip Frequency EMF into Rotor Side When the speed control of three phase induction motor is done by adding resistance in rotor circuit, some part of power called, the slip power is lost as I2R losses. Therefore the efficiency of three phase induction motor is reduced by this method of speed control.
What is rotor induced emf?
3 Rotor induced e.m.f. and current. The rate at which the rotor conductors are cut by the flux, and hence their induced e.m.f., is directly proportional to the slip, with no induced e.m.f. at synchronous speed (s = 0) and maximum induced e.m.f. when the rotor is stationary (s = 1).
What is rotor emf?
Rotor EMF. When the rotor is stationary, the 3-phase induction motor behaves as a 3-phase transformer with secondary winding short circuited. Thus, the per phase induced EMF in the rotor (or secondary) is given by, RotorEMF/Phase,πΈ2=πΈ1Γπ2π1=πΎπΈ1β¦(
How does the rotor of an induction motor rotate?
The rotor of the induction motor rotates in the same direction as that of the rotating magnetic field. Actually when you give 3 -phase supply to the stator windings, a rotating magnetic field is produced.
Why does rotor current flow through rotor bar instead of rotor core?
When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. This rotating magnetic field has a speed which is known as the synchronous speed. This rotating magnetic field induces the voltage in rotor bars and hence short-circuit currents start flowing in the rotor bars.
How is an emf induced?
An emf is induced in the coil when a bar magnet is pushed in and out of it. Movement of a magnet relative to a coil produces emfs as shown. The same emfs are produced if the coil is moved relative to the magnet. The greater the speed, the greater the magnitude of the emf, and the emf is zero when there is no motion.
Where is emf induced in motor?
A motor has coils turning inside magnetic fields, and a coil turning inside a magnetic field induces an emf. This emf, known as the back emf, acts against the applied voltage that’s causing the motor to spin in the first place, and reduces the current flowing through the coils of the motor.
What is rotor EMF?
What is frequency of rotor induced emf?
The frequency of the induced emf in rotor is? Explanation: The induced frequency will be f = P(Ns-Nr)/2. f = 4(1500-1450)/2 = 100 Hz.
Does the rotor of an induction motor induce EMF to the stator?
The rotor does not induce emf to the stator. It is the opposite. βAn induction motor is an AC electricmotor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic inductionfrom the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor.β.
What is the equation of induced voltage in the rotor?
The equation of induced voltage in the rotor is Eb = s*E. Where is E = stator emf. s = slip of the induction motor. However there is a difference in the effect of back emfs of Induction motor and DC motor. In DC motor at the starting the back emf is zero, while in Induction machine Back emf is maximum.
What is an induction motor?
βAn induction motor is an AC electricmotor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic inductionfrom the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor.β
What is the rotor frequency of 3-phase induction motor?
But, the frequency of the current and EMF in the rotor circuit of the 3-phase induction motor is variable and depends upon the difference between the synchronous speed (NS) and the rotor speed (Nr), i.e., on the slip. Thus, the rotor frequency is given by, π π = (π π β π π) π 120 β¦ (2)