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.
What are the main characteristics of synchronous motor?
- 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.
What is principle of synchronous motor and write characteristic feature of synchronous motor?
Working Principle of Synchronous Motor
The operation of a synchronous motors is that the rotor follows the rotating magnetic field of a stator and rotates at a speed approaching it . The rotor winding is excited by a DC source and the stator winding is excited by AC source.
What is synchronous motor PDF?
Synchronous motor is a doubly fed . motor ; three-phase power is given to. the stator while the rotor is fed from a. DC source for excitation of the field.
What is the advantage of a synchronous motor?
Advantage or Merits:
One of the major advantage of using synchronous motor is the ability to control the power factor . An over excited synchronous motor can have leading power factor and can be operated in parallel to induction motors and other lagging power factor loads thereby improving the system power factor.
What is the 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 are the methods of starting synchronous motor?
- Using Pony Motors : By using the small pony motors like a small induction motor, we can start the synchronous motor. ...
- Using Small D.C. Machine : ...
- Using Damper Winding : ...
- As a Slip Ring Induction Motor ( Synchronous Induction Motor ) :
What are physical characteristics of synchronous machine?
Synchronous motors have the following characteristics: • A three-phase stator similar to that of an induction motor . Medium voltage stators are often used. source of direct current (DC). Both brush-type and brushless exciters are used to supply the DC field current to the rotor.
What are the main parts of synchronous machine?
The principal components of a synchronous motor are the stator and the rotor . The stator of synchronous motor and stator of induction motor are similar in construction. With the wound-rotor synchronous doubly fed electric machine as the exception, the stator frame contains wrapper plate.
What is synchronous motor PPT?
A synchronous motor is electrically identical with an alternator or AC generator . A given alternator ( or synchronous machine) can be used as a motor, when driven electrically. ... It runs either at synchronous speed or not at all i.e. while running it maintains a constant speed.
How is torque produced in a synchronous motor?
The torque of a synchronous motor is produced by the phase difference between the rotating magnetic field and the rotor . The torque is low when there is a small phase difference between the rotating rotor and the rotating magnetic field.
How does a synchronous motor improve power factor?
A Synchronous Motor can be made to operate at unity and leading power factor by just increasing its excitation voltage i.e. by increasing the field current . This advantage of Synchronous Motor is used to improve the power factor.
Can synchronous motor work as generator?
Originally Answered: Can a synchronous motor work as a synchronous generator? Yes . Simply the three phase supply is removed and only the DC field supply is retained. When the motor is run from external prime mover, they become an alternator or synchronous generator.
What is a disadvantage of a synchronous motor?
Disadvantages of Synchronous Motor
It needs frequent maintenance. External DC source is necessary for providing excitation . Additional damper winding is necessary. Hunting takes place if the load is changed suddenly.
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 .
How do you identify a synchronous motor?
if the slip of the motor is zero or the rotor has the same rotational speed as the stator rotating field , the motor is called AC Synchronous motor. if an AC motor has a slip or there is a difference between the stator field speed and the rotor, the motor is called asynchronous motor.
Why DC supply is used in 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 .
Why damper winding is used in synchronous motor?
The main purpose of using Damper winding in synchronous Machine is to provide starting torque and eliminate damping or hunting . The damper winding is used in Synchronous Motor to provide starting torque and the damper winding is used in the synchronous alternator to eliminate damping or hunting.
What are the essential features of synchronous machine?
- 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.
Why synchronous motor has no starting torque?
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.
Which is the main application of synchronous motor Mcq?
Synchronous Motors MCQ Question 10 Detailed Solution
It is used as a reactive power compensator for power factor correction purposes . A synchronous motor running with no load will lead the current i.e. leading power factor like a capacitor.
What is Synchronous Motor and induction motor?
[What is a synchronous & Induction motors] The electromagnetic motor which converts electrical energy into mechanical work at constant speed is called as a ‘Synchronous Motor’. The electromagnetic motor which converts electrical energy into mechanical work at variable speed is called as a ‘Induction Motor’.
Which of the following characteristics is also called load characteristics of synchronous generator?
External Characteristic (V/I L ):
External characteristics are very important to determine the suitability of a generator for a given purpose. Therefore, this type of characteristic is sometimes also called as load characteristic.
What is synchronous motor speed?
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.
What are the different torques of a synchronous motor?
A synchronous motor is started as induction motor till it runs 2 to 5% below the synchronous speed. Afterwards, excitation is switched on and the rotor pulls into step with the synchronously rotating stator field. The amount of torque at which the motor will pull into step is called the pull -in torque .
What is hunting in synchronous machine?
Hunting is the phenomenon of oscillation of the rotor about its steady state position or equilibrium state in a synchronous motor. Hence, hunting means a momentary fluctuation in the rotor speed of a synchronous motor.
Can we use synchronous motor as alternator?
Construction of a synchronous motor is similar to an alternator (AC generator). A same synchronous machine can be used as a synchronous motor or as an alternator.
How do you control speed of synchronous motor?
However, with the invention of solid-state devices, the frequency of the current fed to the synchronous motor can be varied. We can control the speed of the synchronous motor by changing the frequency of the supply to the motor .
What is the difference between synchronous generator and synchronous motor?
In this psot we will discuss Difference between Synchronous Motor & Synchronous Generator. The motor is a device that is used to transform electrical energy into mechanical energy and generator is used to transform mechanical energy into electrical energy.
Can a synchronous machine running as a motor generate voltage?
To operate the machine as a generator, the rotor is driven by a prime mover. ... This is a two-pole machine, so one cycle of voltage is induced by each revolution of the machine. To generate constant-frequency voltages, the speed of the machine must be held constant at synchronous speed.
