Synchronous Motors
Electrical Engineering
(ELE-232)
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Electrical Engineering - Synchronous Motors, Study notes of Electrical and Electronics Engineering
In this document description about Synchronous Motors, Synchronous Motors Basic features, Synchronous Motor Construction, Some Facts about Synchronous Motor, Synchronous Motor Construction, Synchronous Motors Basic features.
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Synchronous Motors
Electrical Engineering (ELE-232)
Synchronous Motors
Basic features
- (^) As the name implies, a synchronous motor runs at synchronous speed (Ns = 120f/P)
- (^) Same as alternators: Stationary Armature and Rotating Magnetic Field.
- (^) A Three phase input is required for a Synchronous Motor.
- (^) Three phase AC input is taken at Stationary Armature windings.
Synchronous Motors
Basic features
- (^) The speed of rotation is based on the
frequency of the source.
(Ns = 120f/P)
- (^) Since the frequency is fixed, the motor speed
stays constant irrespective of the load or
voltage of 3- phase supply.
Synchronous Motor
Construction
- (^) A synchronous motor is a machine that operates at synchronous speed and converts electrical energy into mechanical energy.
- (^) It is fundamentally an alternator operated as a motor.
- (^) Like an alternator, a synchronous motor has the following two parts: - (^) Rotor - (^) Stator
Synchronous Motor
Construction
- (^) A rotor that has a set of salient poles excited by direct current to form alternate N and S poles.
- (^) The exciting coils are connected in series to two slip rings and direct current is fed into the winding from an external exciter mounted on the rotor shaft.
Synchronous Motor
Construction
- (^) The number of poles determines the synchronous speed of the motor:
Some Facts about Synchronous
Motor
- (^) Salient pole type.
- (^) Not self-starting.
- (^) It is difficult to produce initial starting torque.
- (^) External source is required for starting
- (^) induction motor principle or a separate starting motor for this purpose.
Some Facts about Synchronous
Motor
- (^) It is known as doubly excited machine:
- (^) Stator: By an AC Source:
- (^) Rotor: By as DC Source:
Some Facts about Synchronous
Motor
- (^) How three phase current carrying conductor can produce a rotating magnetic field….
Operating Principle
- (^) Difficult to start Synchronous Motor…..
- (^) No Starting Torque….
- (^) The fact that a synchronous motor has no
starting torque can be easily explained.
Operating Principle
- (^) Motor Input at Rotor Winding: DC Applied voltage
- (^) Motor Input at Stator Winding: 3 Phase AC
- (^) The stator winding produces a rotating field which revolves round the stator at synchronous speed Ns(= 120 f/P). (Ref. Demo)
Operating Principle
- (^) Next Step:…..... DC current is taken for….
- (^) .……..Setting the field poles
- (^) ...……At rotor part
- (^) ..…..…But not rotating at beginning
Operating Principle
- (^) Suppose at any instant, the stator poles are at positions A and B as shown in Fig. MZS FKEE, UMP 19
Operating Principle
- (^) It is clear that poles NS and NR repel each other and so do the poles SS and SR. Therefore, the rotor tends to move in the anticlockwise direction.