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The synchronous motor is a type of AC motor that runs at synchronous speed. The asynchronous motor is a type of AC motor that runs on speed less than the synchronous speed. It operates on the principle of magnetic interlocking between rotor and stator field. it is always less than synchronous speed.
What is difference between synchronous and induction motor?
Synchronous motors require an additional DC power source for energizing rotor winding. Induction motors do not require any additional power source. Synchronous motors require additional starting mechanism to initially rotate the rotor near to the synchronous speed. No starting mechanism is required in induction motors.
What are the examples of asynchronous motor?
All induction motors are asynchronous motors. The asynchronous moniker arises from the slip between the rotational speed of the stator field and somewhat slower speed of the rotor. A squirrel cage rotor from an induction motor. This example is from a small air fan.
What is the main disadvantage of synchronous motors?
Disadvantages or Demerits: Synchronous motors requires dc excitation which must be supplied from external sources. Synchronous motors are inherently not self starting motors and needs some arrangement for its starting and synchronizing. The cost per kW output is generally higher than that of induction motors.
Why do we use synchronous motors?
usually, synchronous motors are used for applications where precise and constant speed is required. While used in high power industrial sizes, these motors perform two important functions. One is as an efficient means of converting AC energy into mechanical energy and the other is Power factor correction.
Why synchronous motors are not self starting?
Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator. Once the rotor nears the synchronous speed, the field winding is excited, and the motor pulls into synchronization.
How does a synchronous motor start?
The motor is first started as a slip ring induction motor. The resistance is gradually cut-off as the motor gains speed. When it achieves near synchronous speed, DC excitation is given to the rotor, and it is pulled into synchronism. Then it starts rotating as a synchronous motor.
What are the main characteristics of a synchronous motor?
Main Features of Synchronous Motors Synchronous motors are inherently not self starting. The speed of operation of is in synchronism with the supply frequency and hence for constant supply frequency they behave as constant speed motor irrespective of load condition.
Where is asynchronous motor used?
Thus, this is all about an overview of an asynchronous motor. These motors are frequently used in 90% of the applications all over the world due to reasons like great robustness and reliability. These motors are used in different moving or rotating machines like lifts, fans, grinders, etc.
Why is it called asynchronous motor?
Because induction motor can not rotate at synchronous speed it always rotate less than synchronous speed. in short, induction motor never rotates at synchronous speed so it called asynchronous motor.
Which is better synchronous or 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 counters?
The one advantage of synchronous counter over asynchronous counter is, it can operate on higher frequency than asynchronous counter as it does not have cumulative delay because of same clock is given to each flip flop.
What is the working principle of synchronous motor?
The principle of operation of a synchronous motor can be understood by considering the stator windings to be connected to a three-phase alternating-current supply. The effect of the stator current is to establish a magnetic field rotating at 120 f/p revolutions per minute for a frequency of f hertz and for p poles.
What is the advantage of synchronous current?
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.
Are synchronous motors AC or DC?
In a synchronous motor, AC power is supplied to the stator to generate a rotating magnetic field. DC power is supplied to the rotor which results in discrete North (N) and South (S) poles.
What are the applications of DC motor?
Application of DC Series motor Cranes. Air compressor. Lifts. Elevators. Winching system. Electric traction. Hair drier. Vacuum cleaner and in speed regulation application.
Why the speed of synchronous motor is constant?
Synchronous motors are constant speed motors. They run at the synchronous speed of the supply. As you can see, the synchronous speed depends on the frequency of the supply and the number of poles of the rotor. Changing the number of poles is not easy, so we do not use that method.
Which motors are not self-starting?
Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator.
Are asynchronous motor self-starting?
The current carrying rotor being placed in a magnetic field experiences a torque and hence begins to rotate in the direction of rotating magnetic field. Thus we see that Induction Motor is self-starting. It does not require nay external mean to rotate.
What is synchronous speed of motor?
The synchronous speed of an AC motor is determined by the frequency of the source and the number of poles. The RPM is calculated by multiplying the frequency times 60 and dividing by the number of pairs of poles. Some motors are designed to operate at synchronous speed.
Which type of starter is used for synchronous motor?
Controllers for synchronous motors have four components: a three-pole starter for the ac stator circuit, a contactor for the dc field circuit, an automatic synchronizing device to control the dc field contactor, and a cage-winding protective relay to open the ac circuit if the motor operates too long without.
Why do we give DC excitation to AC synchronous motor?
When AC supply is given to the stator winding or static armature winding of the synchronous motor it creates a rotating magnetic field. If we give DC supply to the field winding or rotor winding of the synchronous motor then the pole created in the rotor will be constant.
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.
