Synchronous motors. A synchronous engine is one in which the rotor normally rotates at the same velocity as the revolving field in the device. The stator is comparable to that of an induction machine comprising a cylindrical iron frame with windings, usually three-phase, located in slots around the inner periphery.
usually, synchronous motors are used for applications where precise and continuous speed is required. Low power applications of these motors include positioning devices. These are also applied in robot actuators. Ball mills, clocks, record player turntables also make use of synchronous motors.
The principle of operation of a synchronous motor can be understood by taking into consideration the stator windings to be connected to a three-phase alternating-current supply. The result of the stator current can be to establish a magnetic field rotating at 120 f/p revolutions per minute for a frequency of f hertz and for p poles. A direct current in a p-pole field winding on the rotor will also produce a magnetic field rotating at rotor rate. If the rotor acceleration is made equal to that of the stator field and there is no load torque, both of these magnetic fields will have a tendency to align with each other. As mechanical load can be used, the rotor slips back several degrees with respect to the rotating field of the stator, developing torque and ongoing to be drawn around by this rotating field. The angle between the fields increases as load torque is increased. The maximum available torque is accomplished when the angle by which the rotor field lags the stator field can be 90°. Software of more load torque will stall the electric motor.
One benefit of the synchronous electric motor is certainly that the magnetic field of the machine can be produced by the immediate current in the field winding, to ensure that the stator windings have to provide only a power Auto Chèn element of current in stage with the applied stator voltage-i.e., the electric motor can operate at unity power element. This problem minimizes the losses and heating system in the stator windings.