Specifications

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3.3 SLOT INSULATION : Materials used for slot insulation are leatheroid, mica, glass cloth,
and flexible type of micanite. The type of slot insulation will vary according to the capacity of the
machine.
Slot Liner : The slot liner is an insulation sheet cut to the inner dimensions of the slots and
projected on either side of the slots. In some applications, the edges of the slot liner are folded
on either end to prevent them from sliding in the slots, as shown in Fig. 3.8.
Fig.3.8 - Slot Insulation
Coil Separator : When multilayer windings are used, to insulate the winding layers from each
other, coil separators are used, as shown in Fig. 3.8. They should be extended on either side of
the slot.
Packing Strip : The thick insulation paper used in between the slot liner and wedge is called a
packing strip, as shown in Fig. 3.8. This should extend beyond each end of the armature core.
Wedge : It is a solid insulation piece like bamboo or fibre used to prevent the conductors from
coming out of the slots. It should be tightly held in the slots, as shown in Fig. 3.8.
3.4 COIL FORMATION : The annealed copper conductors, normally in round shape, are used
for winding small and medium capacity electrical machines.
Field Coil Formation : Field coils are wound with insulated copper wire whose diameter and
number of turns depend on the exciting voltage and machine capacity. The wire can be wound
on a wooden former that consists of the inner dimensions of the coil.
Stator/rotor/armature Coil Formation : Diamond shaped wooden former is constructed to
the required dimensions, length and width of the coil. The coils are wound over the former with
the help of the coil winding machine. All coils are wound identically. The number of turns depends
on the voltage rating of the machine where as the conductor size depends on the current rating.
3.5 REVOLVING ( ROTOR) WINDING : The winding that rotates with either the rotor of an
induction machine or the armature of a dc machine, is called a revolving winding.
3.6 STATIONARY ( STATOR) WINDING : The winding wound either on the stator of an induction
machine or on the field system of a dc machine is called a stationary winding.
3.7 DC ARMATURE WINDINGS : There are two types of dc armature windings, namely the lap
and wave windings. For development of dc armature windings, few pitches related to the types
of dc armature windings are Back pitch, Front pitch and Winding pitch.