Speed of synchronous motor depends upon

A) to provide starting torque only. D) to prevent hunting and provide the starting torque. When the excitation of an unloaded salient-pole synchronous motor suddenly gets disconnected. A) The speed varies directly only in proportion to the number of its poles.

B) The speed is independent of the frequency of the voltage supply.

Clearly you have to apply power to the motor and you have to apply enough supply voltage to overcome motor losses.

Once you do that the motor works synchronously off-load but when mechanical load is applied to the shaft there has to be enough current in the source to be able to supply mechanical .

The synchronous speed is the speed of the revolution of the magnetic field in the stator winding of the motor. It is the speed at which the electromotive force is. The frequency of the generated voltage depends upon the number of field poles and on the speed at which the field poles are rotated. Detailed webpage version the video is given below.

As the name suggests Synchronous motors are capable of running at constant speed irrespective of the load acting on them. Unlike induction motors where speed of the motor depends upon the torque acting on them, synchronous motors have got constant . The speed at which an induction motor will operate depends on the input power frequency and the number of electrical magnetic poles in the motor. A synchronous motor must be brought upto synchronous speed before it is loaded. Then increased torque increases the rotor speed , and the motor again regains the synchronous speed , but with the larger torque angle.

In the synchronous motor , the basic magnetic field is obtained by direct current excitation rather than through the air-gap from the. The required pull-in torque depends upon the load torque and the. That depends upon grid frequency and number of coupled poles. In case of induction motor the rotor speed will always less than synchronous speed.

Because of slip, the rotor speed can not catch the synchronous speed. The rotor speed is directly depends upon the load. The load increases, the rotor speed . However, induction motors such as squirrel-cage or wound-rotor motors rotate slightly below synchronous speed , since they depend on electromagnetic induction between the stator and rotor.

The torque produced by three phase induction motor depends upon the following three factors:. Putting the value of flux φ, rotor current I power factor cosθin the equation of torque we get, Combining similar term we get, Removing proportionality constant we get, Where, ns is synchronous speed in r. Here we need to define what is synchronous speed. Before discussing the methods to control the speed of three phase induction motor one should know the basic formulas of speed and torque of three phase induction motor as the methods of speed control depends upon these formulas.