- 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 are the main application of synchronous motor?
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 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 are the main parts of synchronous motor?
A synchronous motor is generally made up of two parts,
a stator the stationary part of the machine that carries the armature winding in
which the voltage is generated, and a rotor the rotating part of the machine that produces the main field flux.
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 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.
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 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 is the difference between synchronous and asynchronous motor?
Synchronous motor is a machine whose rotor speed and the speed of the stator magnetic field is equal. Asynchronous motor is a machine whose rotor rotates
at the speed less than the synchronous speed
. … Synchronous motor does not have slip.
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 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.
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 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’.
What is Xs in synchronous motor?
Figure 1: Per-phase equivalent circuit for synchronous generator. Armature resistance Ra is neglected and Xs = ωeLs is
the stator synchronous reactance
. Often, we drop the “f” subscript and simply write the generated voltage as ˆEa. Its angle, δ is called the torque angle or power angle.
What are advantages and disadvantages of synchronous motors?
Its
starting torque is zero
. These motors have tendency to hunt. When loading on the synchronous motor increases beyond its capability, the synchronism between rotor and stator rotating magnetic field is lost and motor comes to halt. Collector rings and brushes are required resulting in increase in maintenance.
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.
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 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 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.
What are types of synchronous motor?
- Non-excited motors.
- DC-excited motors.
- Examples.
- Use as synchronous condenser.
- Steady state stability limit.
- Other.
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 main difference between synchronous and asynchronous transmission?
| Basis for Comparison Synchronous Transmission Asynchronous Transmission | Transmission manner Sends data in the form of blocks of frames Sends 1 byte or character at a time | Synchronization Present with the same clock pulse. Absent | Implemented by Hardware and software Hardware only | Transmission speed Fast Slow |
|---|
What is the speed regulation of a synchronous motor?
Synchronous motor running at the constant synchronous speed. Therefore there is no speed loss, so the speed regulation of synchronous motor
is zero
.
What is the difference between synchronous and asynchronous?
Synchronous = happens at the same time.
Asynchronous = doesn’t happen at the same time
.
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.
What is the difference between synchronous motor and generator?
Almost all aspects of synchronous motor like construction, working, is similar to the synchronous generator but the difference is that
generator converts mechanical power into electrical and motor converts electrical into mechanical
. … The resultant circuit of a synchronous motor is shown in a given figure.
How many categories can the synchronous motor be divided into?
Explanation: The synchronous motors can be divided into
5 types
of categories. They are hydro-generators, turbo-alternators, engine driven generators, motors, compensators.
How do you calculate torque of a synchronous motor?
- The stator and rotor iron have infinite permeability. …
- All the magnetic flux crosses the air gap perpendicularly. …
- The air gap length is very small when compared to the axial length of synchronous machine. …
- Only fundamental sine component of stator and rotor mmf wave is considered.
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.
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 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.
What is the difference between synchronous and induction generator?
Difference between synchronous generator and induction generator. In a synchronous generator, the waveform of generated voltage is synchronized with (directly corresponds to) the
rotor speed
. … Induction generator takes reactive power from the power system for field excitation.
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.
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.
What is the V curve of synchronous motor show relationship between?
Detailed Solution. Synchronous motor: V curves for synchronous motor give the relation between
armature current and DC field current
.
What is the synchronous impedance?
The synchronous impedance may be defined as
the vector sum of the armature resistance and synchronous reactance
. It is denoted as Z
s
.
What is EF in synchronous generator?
E
f
which denotes
excitation voltage
. V
t
which denotes terminal voltage. I
a
which denotes the armature current. … r
a
which denotes the armature per phase resistance.
