The three-phase synchronous motor is a unique and specialized motor. As the name suggests, this motor runs at a constant speed from no load to full load in synchronism with line frequency. … This attraction exerts a torque on the rotor and causes it to rotate at the synchronous speed of the rotating stator field.
How is a 3 phase synchronous motor generally started?
When 3 phase power is supplied to the motor, the motor starts running as an induction motor at a speed below synchronous speed. After some time DC supply is given to the rotor. The motor gets pulled into synchronism after some instant and starts running as a synchronous motor.
What is a synchronous motor used for?
Synchronous motors are normally used in applications in which a constant and precise speed is required. Typical applications of these low power motors are positioning machines. They are also used in robot actuators. Synchronous motors are also used in ball mills, watches, record players, and turntables.
Is synchronous motor single phase or three-phase?
The operation of a synchronous motor is due to the interaction of the magnetic fields of the stator and the rotor. Its stator winding, which consists of a 3 phase winding, is provided with a 3 phase supply, and the rotor is provided with a DC supply.
At what speed do synchronous motors run?
The 3-phase 4-pole (per phase) synchronous motor will rotate at 1800 rpm with 60 Hz power or 1500 rpm with 50 Hz power.
What is the main disadvantage of synchronous motors?
Disadvantages of Synchronous Motor
Synchronous motors require dc excitation which is supplied from external sources. These motors are not self-starting motors and need some external arrangement for its starting and synchronizing. The cost per kW output is commonly higher than that of induction motors.
Which is better synchronous or asynchronous motor?
Synchronous motor is costly as compared to Asynchronous motor. Efficiency of Synchronous motor is greater than Asynchronous motor. By changing excitation the power factor of the Synchronous motor can be adjusted accordingly as lagging, leading or unity, whereas Asynchronous motor runs only at a lagging power factor.
What are the advantages of synchronous motor?
The advantages of the synchronous motor are the ease with which the power factor can be controlled and the constant rotational speed of the machine, irrespective of the applied load. Synchronous motors, however, are generally more expensive and a d.c. supply is a necessary feature of the rotor excitation.
Why is it called synchronous motor?
Definition: The motor which runs at synchronous speed is known as the synchronous motor. The synchronous speed is the constant speed at which the motor generates the electromotive force. The synchronous motor is used for converting the electrical energy into mechanical energy.
What is a 4 pole 3 phase motor?
With a 4-pole machine, the rotor will move from 1 pole pair to the next in 1 AC supply cycle, so will do half a rev in one supply cycle – the synchronous speed is therefore 50/2 revs per second, or 1500 rpm. A 4-pole induction motor will have a nominal speed of 1450 rpm or thereabouts.
What are the applications of 3 phase synchronous motor?
Due to constant speed characteristics, it is used in machine tools, motor generator sets, synchronous clocks, stroboscopic devices, timing devices, belt driven reciprocating compressors, fans and blowers, centrifugal pumps, vacuum pumps, pulp grinders, textile mills, paper mills line shafts, rolling mills, cement mills …
Is 3 phase induction motor is self-starting?
Three-phase induction motor is self-starting, because winding displacement is 120 degrees for each phase and supply also has 120 phase shift for 3-phase. It results in a unidirectional rotating magnetic field is developed in air gap which causes 3-phase induction motor to self-start.
What determines the speed of a 3 phase motor?
The rotating speed of an electric motor depends on two factors: its physical construction, and the frequency (Hz) of the voltage supply. Electrical engineers select the speed of a motor based on the needs of each application, similar to how the mechanical load determines the horsepower required.
What happens to synchronous motor if only field is excited?
As the Field Winding is excited by AC source, an alternating / pulsating magnetic flux will be produced. … The armature conductor at Stator will not see any change in flux due to backward rotating field flux and hence no EMF will be generated in the Armature Terminal of Alternator.
Which speed is synchronous speed in 3 phase induction motor?
Solution. The frequency of 3-phase supply teu le frequency of 3-phase supply led to the induction motor is determined from the speed of the alternator and its number of poles. Supply frequency, 1 = NP/120 = 1000 x 6/120 = 50 Hz Synchronous speed.