Download Prof: URVISH MEVADA

TITLE OF CONCEPT
AC MACHINE
WINDING
DESIGN.

PREAPED BY :
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GUIDED BY:
Prof: URVISH MEVADA
ELEMENTARY CONCEPT
 Electromechanical energy conversion occurs when
changes in the flux linkages λ resulting from
mechanical motio
Magnetic Field
Horizontal axis
d
e(t ) 
dt
e(t)
 Armature winding: AC current carrying winding
 Synchronous machine
 Induction machine
 Armature winding is stator winding (stationary)
 Synchronous machine Field winding is on the rotor
INTRODUCTION TO AC MACHINES
AC Machines: Synchronous Machines and Induction Machines
Synchronous Machines:
•Two-pole, single phase machine
•Rotor rotates with a constant speed
•Constraction is made such that air-gap
flux density is sinusoidal
•Sinusoidal flux distribution results with
sinusoidal induced voltage
(a) Space distribution of flux density and
(b) corresponding waveform of the generated voltage for the single-phase
generator.
•Four-pole, single phase machine
•a1,-a1 and a2,-a2 windings connected in
series
•The generator voltage goes through two
complete cycles per revolution of the
rotor. The frequency in hertz will be twice
the speed in revolutions per second.
p
 ae   a
2
p n
fe 
2 60
n: rpm
fe: Hz
Field winding is a two-pole
distributed winding
Winding distributed in multiple slots
and arranged to produce sinusoidal
distributed air-gap flux.
Elementary two-pole cylindricalrotor field winding.
Schematic views of three-phase generators: (a) twopole, (b) four-pole, and (c) Y connection of the
windings.
Induction Machines:
•The stator winding excited by
ac current. The current
produces a rotating magnetic
field which in turn produces
currents in rotor conductors due
to induction.
•These machines mostly used
as motors.
•Rotor windings are short
circuited (electrically) and
frequently have no external
connections.
•Stator and rotor fluxes rotate in
synchronism with each other
and that torque is related to the
relative displacement between
them.
•Rotor does not rotate
synchronously
Typical induction-motor speed-torque
characteristic.
Inside View of An Induction Motor and Winding
Windings placed in stator slots
AC Machines:
The mmf of one phase of a distributed two-pole,
three-phase winding with full-pitch coils.
4  k N ph ia 
p 

 cos  a 
Fag1  

p
2 

k
Winding factor (usually between
0.85 and 0.95)
N ph Series turns per phase
MAGNETIC FIELDS IN ROTATING
MACHINERY
The air-gap mmf and
radial component
of Hag for a concentrated
full-pitch winding.
4  Ni 
H ag1    cos  a
  2g 
Distributed winding:
4  k w N ph ia   p 
 cos  a 
H ag1  
 gp  2 
The air-gap mmf of a distributed winding on the rotor
of a round-rotor .
Fag1 
4  kr N r I r 
p 

 cos  r 
 p  2 
Finite-element solution of the magnetic field distribution in a salient-pole ac
machine. Field coils excited; no current in armature coils. (General Electric
Company.)
Flux created
by a single
coil side in
a slot.
(a) full-pitch coil and
(b) fractional-pitch coil
Elementary
generator
Elementary
cylindrical-rotor,
two-phase
synchronous
machine