What is the speed of the rotor magnetic field with respect to rotor?
(i) Frequency of stator current = 50 Hz (ii) Speed of rotor magnetic field w.r.t. rotor = (N. -N) = 1500 – 1440 = 60 rpm. Rotor magnetic field is in the same direction of rotation of rotor. (iii) Speed of stator magnetic field w.r.t. stator = N = 1500 rpm.
What is the speed of rotating magnetic field?
Speed is important to the rotating magnetic field of an AC motor. It is known as “synchronous speed.” This speed is calculated by dividing 120 times the frequency (F) by the number of poles (P). As an example, the synchronous speed for a 2-pole motor operated at 60 Hz is 3,600 RPM.
How do you find the speed of an induction rotor?
The synchronous speed of the rotor in RPM N = 120f/P where f is the frequency of the stator current and P is the number of poles. The operating speed No = N – Ns where Ns is the slip speed.
What is the speed of the rotating magnetic field in RPM produced by the stator currents?
Hence the magnetic flux in the stator is said to rotate at synchronous speed (Ns). For example, for a 6-pole, 50 Hz, 3-phase induction motor, Ns = 120 * 50/6 = 1000 rpm. It means that the flux rotates around the stator at a speed of 1000 rpm.
What is rotor speed?
Rotor speed depends, in part, on rotor diameter. Rotor speeds typically lie in the 120–210 m/s range, but mostly between 150 and 190 m/s, with a tendency to be higher with a smaller rotor diameter [6].
What is the relative speed between the stator magnetic field and rotor in the induction motor?
zero
In synchronous machine, the rotor and stator fields rotate at synchronous speed and hence the relative speed between them is zero. In DC machine, both the fields rotate at same speed and hence the relative speed between them is zero.
What is the speed of the rotor field in space?
The speed of rotor field flux is synchronous speed (Ns) and the speed of the stator is zero as the stator doesn’t rotate. The relative speed between the rotor field and stator is synchronous speed and it is 1500 rpm.
What is rotating magnetic field in induction motor?
The rotating magnetic field is produced by the three-phase current of the stator in the actual three-phase induction motor. It can be replaced by permanent magnets in a permanent magnet synchronous motor. The three-phase windings of the inner stator are spaced 120° electrical degrees apart.
What is rotor speed and synchronous speed?
The synchronous speed refers to the stator rotating magnetic field, which depends on the number of poles and frequency. The other speed is the rotor’s. The rotor speed will be always slower than the stator speed, we call it slip. Without the slip, the squirrel cage induction motor doesn’t have torque.
How do you calculate rotor speed on a 3 phase induction motor?
Rotor speed of an induction motor is given by
- N r = (1 – s) N s
- N r = (1 + s) N s
- N r = (s 2 – 1) N s
- N r = (s – 1) N s
What is the speed of rotating magnetic field produced in the stator Mcq?
Explanation: Rotating field speed (Ns) = 120f/(p r.p.m) = synchronous speed.
Why rotor speed is less than synchronous speed?
Actual speed of the induction motor will be less than the synchronous speed. The reason for this is if the armature turns exactly at synchronous speed, then the magnetic field of the stator windings no longer cuts the rotor windings. Under this condition, no current would be induced to the rotor windings.
What is rotor speed in 3 phase induction motor?
In a three-phase induction motor, The stator is stationary, and the rotor is a rotating part. Both the stator field and rotor field rotate with synchronous speed. The rotor rotates with a speed less than synchronous speed.
When the relative speed between the magnetic fields of stator and rotor does is zero under steady-state operation?
In synchronous machine, the rotor and stator fields rotate at synchronous speed and hence the relative speed between them is zero. In DC machine, both the fields rotate at same speed and hence the relative speed between them is zero.
What happens to the relative speed between rotor and stator when the magnetic flux increases?
✔Ans = The speed of rotor gradually increases and tries to catch up with the speed of rotating magnetic field, but it fails to reach synchronous speed, because if it catches up with speed of magnetic field, relative speed becomes zero and hence no EMF will be induced in the rotor conductors, the torque becomes zero.
What is the speed of stator rotating magnetic field with respect to rotor rotating magnetic field?
The relative speed between the rotor field and stator is synchronous speed and it is 1500 rpm.
Why is it not possible for the rotor speed to be equal to that of the revolving field speed?
It is impossible for the rotor of an induction motor to turn at the same speed as the rotating magnetic field. If the speeds were the same, there would be no relative motion between the stator and rotor fields; without relative motion there would be no induced voltage in the rotor.
What is rotor speed formula?
s = N s − N r N s. ⇒ N r = (1 – s) N s. Where Ns is the synchronous speed. And Nr is the rotor speed. The frequency of rotor current = sf.
Which speed is synchronous speed in 3 phase induction motor?
In an induction motor, the speed at which the rotating magnetic field (RMF) rotates is known as synchronous speed (NS).
What is speed control of induction motor?
Induction motor speed control is a process of manipulating currents in an induction motor to regulate speed. While often used in fixed frequency applications, induction motors are popular for variable frequency applications such as industrial drives and electric vehicles.
What is the speed of magnetic field in induction motor?
Speed of Rotating Magnetic Field in Induction Motor The magnetic field in three phase induction motor (RMF) rotates at a constant speed called synchronous speed (Ns), which is given by, N S = 120f 1 /P RPM where f 1 = Frequency of stator supply
What is the speed of rotor with respect to stator rotating field?
As the speed of the stator rotating magnetic field is Ns, the speed of rotor with respect to the stator rotating magnetic field is – sNs. The value of s will depend on the load. NOTE: The speed of the rotor rotating field with respect to the stator is Ns and with respect to the stator rotating magnetic field is zero.
What is the difference between synchronous and induction motor?
Whereas a synchronous motor’s rotor turns at the same rate as the stator field, an induction motor’s rotor rotates at a somewhat slower speed than the stator field. The induction motor stator’s magnetic field is therefore changing or rotating relative to the rotor.
What is the synchronous speed of magnetic field?
The speed of the rotating magnetic field is known as synchronous speed (NS). The value of synchronous speed depends upon the number poles (P) on the stator and the supply frequency (f).