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What is the Speed of Rotating magnetic field (r.m.f) Øs produced in the stator?
Variable Speed
Synchronous Speed
Asynchronous Speed
Depends on Load
Synchronous Speed
The speed of the rotating magnetic field (r.m.f) produced in the stator of an induction motor is known as synchronous speed. This speed is constant and depends solely on the frequency of the supply voltage and the number of poles in the stator without being affected by the load.
The speed of the rotating magnetic field (r.m.f) produced in the stator of an induction motor is known as synchronous speed. This speed is constant and depends solely on the frequency of the supply voltage and the number of poles in the stator without being affected by the load.
Ns=P120×f — Synchronous speed calculation
Synchronous speed is calculated using the formula Ns=P120×f, where Ns is the synchronous speed in RPM, f is the frequency of the supply in Hz, and P is the number of poles. The rotating magnetic field is generated by the alternating current in the stator windings, creating a magnetic field that rotates at synchronous speed.
Synchronous speed is independent of load.
It is determined by the supply frequency and number of poles.
Provides constant speed operation.
Efficient for various industrial applications.
Cannot operate below synchronous speed.
Requires specific design for speed control.
Used in synchronous machines.
Common in applications requiring precise speed.
Standard synchronous speed for 50 Hz supply and 4 poles is 1500 RPM.
Option A is incorrect because the speed is not variable; it is constant for a given frequency and pole configuration.
B is correct — The speed of the rotating magnetic field is known as synchronous speed, which is a fixed value based on frequency and number of poles.
Understand the relationship between frequency, number of poles, and synchronous speed, as it frequently appears in various engineering problems.