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The synchronous motor consists of the stator (armature), end shields and brush assembly, rotor (field), and damper windings. The stator in this motor consists of three phase coils mounted on the stator frame, to form an even number of stator poles and they are 120 degrees apart. The stator windings leads are brought out to a terminal box on the frame, while the rotor contains both the fields and amortisseur windings. The wounded field windings form salient field poles, with alternate polarity and of the same number as the stator poles. The dc source energizes the field circuit. The synchronous motors are fitted with a starting windings called an amortisseur windings, which consists of copper bars fixed in the laminated rotor core of each of the field poles, and brazed to two end rings one on each side of the rotor. The job of supporting the rotor is for the end shields, where the brush assemblies are important to supply dc current to the rotor field circuit.

When a three-phase voltage is applied to the stator windings of the synchronous motor, a rotating magnetic field will be produce. The speed of this magnetic field known as the synchronous speed and this speed depends only on the frequency and the number of stator poles, where the given formula explains the relationship:

Speed = Frequency * 60 / Number of Poles

A starting torque will be produced, when the rotating magnetic field cuts the damper cage windings. The same as in the squirrel cage induction motor, where its speed will increase to a value less than the synchronous speed.

If the rotor field windings were excited from an external dc supply, fixed poles of alternate polarity would be set up in the rotor core. The unlike poles will be attracted from the rotating stator field, and the rotor will be pulled into synchronism or locked into position with the rotating magnetic field. At this moment the rotor will be rotating along at a synchronous speed. The dc rotor field is applied only after the rotor has speeded up to about 95 percent of the synchronous speed.


The Synchronous Motor The synchronous motor consists of the stator (armature), end shields and brush assembly, rotor (field), and damper windings. The stator in this motor consists of three phase coils mounted on the stator frame, to form an even number of stator poles and they are 120 degrees apart. The stator windings leads are brought out to a terminal box on the frame, while the rotor contains both the fields and amortisseur windings. The wounded field windings form salient field poles, with alternate polarity and of the same number as the stator poles. The dc source energizes the field circuit. The synchronous motors are fitted with a starting windings called an amortisseur windings, which consists of copper bars fixed in the laminated rotor core of each of the field poles, and brazed to two end rings one on each side of the rotor. The job of supporting the rotor is for the end shields, where the brush assemblies are important to supply dc current to the rotor field circuit. When a three-phase voltage is applied to the stator windings of the synchronous motor, a rotating magnetic field will be produce. The speed of this magnetic field known as the synchronous speed and this speed depends only on the frequency and the number of stator poles, where the given formula explains the relationship: Speed = Frequency * 60 / Number of Poles A starting torque will be produced, when the rotating magnetic field cuts the damper cage windings. The same as in the squirrel cage induction motor, where its speed will increase to a value less than the synchronous speed. If the rotor field windings were excited from an external dc supply, fixed poles of alternate polarity would be set up in the rotor core. The unlike poles will be attracted from the rotating stator field, and the rotor will be pulled into synchronism or locked into position with the rotating magnetic field. At this moment the rotor will be rotating along at a synchronous speed. The dc rotor field is applied only after the rotor has speeded up to about 95 percent of the synchronous speed.