HALDIA INSTITUTE OF TECHNOLOGYSYNCHRONOUS MACHINE

BY:-Mitesh kumarRoll no. :- 13/EI/26

Univesity Roll no. :- 10300513026Applied Electronics & Instrumentation

Engg.

Introduction•A synchronous machine is a most important type of electric machine. 

•Synchronous Machine used at generating stations are known as Synchronous Generators or Alternators

•Synchronous motors are widely used in Industries and are well known for their const. speed operation

•Electromechanical energy conversion occurs whenever a change in flux is associated with mechanical motion

Construction of Synchronous MachineIt consists of:

StatorRotorField Windings (On rotor)Armature Windings (On Stator)

Diagram

Stator It is a stationary member

It is the cylindrical portion inside which the rotor rotates

An air gap is provided between the stator and the rotor

Armature winding are 3 phased and are housed in the slots cut in the stator

It consists of cast iron stator frame, a cylindrical laminated , a cylindrical laminated and uniformly slotted core

Rotor Rotor is the rotating part of the machine

Can be classified as: (a) Cylindrical Rotor and (b) Salient Pole rotor

Large salient-pole rotors are made of laminated poles retaining the winding under the pole head.

Armature Windings (On Stator)Armature windings connected are 3-phase and are either star or

delta connected

The windings are 120 degrees apart and normally use distributed windings

The 3-phase armature winding is distributed in the slots along the armature air gap periphery

For example: Consider that we have 18 slots, 2-pole 3-phase winding..

Hence we have 9 slots/per pole as shown figure

The winding diagram of phase ‘a’ can be shown as:

Similarly, phase ‘b’ and phase ‘c’ are distributed in same manner

Field Windings (on Rotor)The field winding of a synchronous machine is always energized

with direct current

Under steady state condition, the field or exciting current is given

Ir = Vf/Rf

Vf = Direct voltage applied to the field winding Rf= Field winding Resistance

The mmf-phase graph can be drawn as:This implies that per phase emf is getting divided in each phase.

When all the 3-phase are connected then mmf-phase graph for each phase is displaced by 120 degrees

Distribution Factor (Kd)

Mostly all the synchronous machines use Distributed winding

 Attempt is made to use all the slots available under a pole for the winding which makes the nature of the induced e.m.f. moe sinusoidal

Consider a sync. Machine with 3-phase winding, Slots, s= 18 slotsPoles=2slots per pole, g= s/p= 9slots/pole/phase= g/3 = 3

Thank you