synchronos machines
TRANSCRIPT
Outlines:
Introduction
Construction
Working principle
Types of Synchronous Machine
Comparison between cylindrical rotor
type generator and Salient pole rotor
type generator
A synchronous machine is an AC machine whose speed is proportional to the frequency of armature current
A machine which rotates at a speed fixed by the supply frequency and the number of rotor poles is called synchronous machine
It always runs at synchronous or constant speed and has no slip
Synchronous machine includes synchronous generators and synchronous motors
A Synch. Generator consists of two main parts;
1) Stator and
2) Rotor
Stator:- The stator is the stationary parts part of the
Synch. Generator
It works as a armature in synchronous machine
The armature winding is housed in it
Rotor:
Rotor is the rotating part of the synchronous
machine
It work as a field of the synchronous machine
Field system is rotating in the synchronous
machine
Field winding is housed on it
Field winding is excited by DC supply through
brushes and slip ring
It works on the principle of Electromagnetic
induction
In the synchronous generator field system is
rotating and armature winding is steady.
Its works on principle opposite to the DC
generator
High voltage AC output coming from the
armature terminal
Generators:-Hydro-generators (Salient Pole Type): The Synchronous generators driven by water
turbines are known as hydro generators orWater wheel generators
They have rating upto 750 MW and are drivenat speeds ranging from 100 to 1000 RPM
Turbo-alternators (Cylidrical Rotor Type or Wound Rotor Type):
They are driven by steam turbines
The efficiency of steam turbine is high at largespeeds, the turbo-alternators are designed forspeed upto 3000 RPM. Turbo-alternators haveratings upto 1000MW
Engine Driven Generators: These generators are driven by different forms of
combustion engines at speed upto 1500 RPM andrating upto 20 MW
These generators are driven by gas turbines havehigher speeds and also higher power ratings
Motors:-Synchronous Motors: Synchronous motors may be either plain synchronous
machines or synchronous induction machines
The plain Synchronous machine with salient pole iscommonly used
Synchronous motors have some define advantagesover induction motors and these include constantspeed operation, Power factor control and highoperating efficiency
- Also Synchronous motors prove to be cheaperthan induction motors for high power lowspeed applications
- The applications of Synchronous machinesinclude constant speed drives forcompressors, blowers, low head pumps
Compensators:- Synchronous compensators are used for
control of reactive power in power supplynetworks
- They are designed for ratings upto 100 MVArand speed upto 3000 RPM
Synchronous generators are classified in two category according to its rotor construction:
1) Cylindrical Rotor Type
2) Salient pole Rotor Type
Cylindrical Rotor Type:-
This type machines are High speed machines (1000 to 3000 RPM)
This type machine has Small diameter and is large axial length
This type of machines are used in Thermal power plant and gas turbine power plant Where speed requires high
Cylindrical rotor:-
Cylindrical rotor does not have poles that are projecting out.
The air gap between the stator and rotor is uniform.
The smooth cylindrical rotor has small no of poles.
Cylindrical rotors are mechanically strong.
They have small diameters and large axial length.
The prime movers used are steam turbines and electric motors.
They are preferred for high speed alternators which range from 1000 to 3000 RPM
Salient Pole rotor:-
Salient pole rotor does have poles that are projecting out from surface.
The air gap between the stator and rotor is non-uniform.
The salient pole rotor has large no of poles.
Saline Pole rotors are mechanically weak.
They have large diameters and small axial length.
The prime movers used are IC engines and law speed turbine.
They are preferred for law speed alternators which range from 100 RPM to 500 RPM