introduction to rotating machines

Mr. D. GaneshElectrical Science – II

INTRODUCTION TO ROTATING MACHINES

BASIC MACHINE TYPES :



DYNAMICALLY INDUCED EMF :

Electromechanical energy conversion takes place whenever a change in flux linkages is associated with mechanical motion.

Voltage is generated in a coil when there is a relative movement between the coil and magnetic field.

The Field Winding, which are the primary source of flux in the machine. They are arrange to produce cyclic North-South space distribution of Poles.

Coils are several in number in practical machines and are suitably distributed and connected in series/parallel and in star/delta 3-φ connection to give desired Voltage and to supply rated Current; this arrangement is called Armature Winding.



WHERE TO PLACE FIELD & ARMATURE WINDINGS ?

Stationary Member Rotating Member

STATOR ROTOR



ROTATING MACHINES :

Electric Generator (TPM=TG) : TPM :Prime mover Torque TG: Generator Torque

Electric Motor (TM=TL) : TM :Motor Torque TL: Load Torque



CONSTRUCTIONAL FEATURES :

STATOR ROTOR

Field Winding Armature WindingIn General

In Case of Synchronous Machines

Field WindingArmature Winding

These are DC exited to produce alternate N-S poles in pairs

The interaction between primary field and current carrying armature conductors causes production of torque of electromagnetic origin.



ROTOR

Salient-pole Rotor

Non-Salient-pole Rotor (Cylindrical Rotor)

For Low Speed Applications

For High Speed Applications



SYNCHRONOUS

MACHINE

1. Field wdgs are placed on rotor and stator carries armature wdgs.

2. The field wdgs are excited through slip-rings from a DC Source.

3. Generally a small DC Generator called exited is coupled to the shaft of the synchronous machine.

alternator.swf



DC MACHINE

1. Field wdgs are placed on stator and Rotor carries armature wdgs.

2. AC voltages and Currents induced in the armature wdg has to converted to DC using rotational mechanical converter called commutator.



INDUCTION

MACHINE1. The stator carries 3-φ wdg , which when excited by 3-φ

ac source that sets up rotating flux pattern with N-S poles in the air-gap at synchronous speed.

2. Armature wdgs are short circuited.



FLUX DENSITY DISTRIBUTION IN ELECTRICAL MACHINES:

Flat-topped wave

To generate Sinusoidal flux , the pole faces in

such a machine are there fore CLAMPERED.



ELECTRICAL Vs MECHANICAL ANGLES:

θele = (P/2) θ mech



FLUX DENSITY DISTRIBUTION IN ELECTRICAL MACHINES:

Another method of achieving a

nearly sinusoidal B-wave is to use

cylindrical rotor structure.



THREE PHASE ALTERNATOR (GENERATOR )- WINDING TYPES



THREE PHASE ALTERNATOR (GENERATOR )- WINDING TYPES

θele = (P/2) θ mech



TYPES OF WINDINGS



TYPES OF WINDINGS



TYPES OF WINDINGS



TYPES OF WINDINGS



TYPES OF WINDINGS



TYPES OF WINDINGS





































































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introduction to rotating machines