Specifications

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3. DETAILS OF WINDING
3.1 DETAILS ABOUT THE WINDING COIL
A length of wire lying in the magnetic field and in which an emf is induced is called a coil.
The coils used in windings are shown in Fig. 3.1.
Fig. 3.1 (a) represents a coil with only one turn in it. Each coil has active and inactive sides.
A coil can in general have any number of turns. A single turn/coil has two active sides, or
otherwise called as conductors. Similarly, a two turn coil has four conductors and a three turn
coil has 6 conductors. Generally, the total number of conductors per coil,
Z
C
= 2T 3.1
and, the total number of conductors for a given machine
Z = Z
C
C 3.2
where Z
C
= total number of conductors per coil
C = number of coils
Z = total number of conductors
T = number of turns per coil
Fig, 3.1 (b) represents multi turn coil.
Active side of a coil : It is the part of a coil which lies in the slots under a magnetic poleand emf
is induced in this part only. In Fig. 3.1 (a), coil sides AB and CD are called as active sides. For
a double layer winding, one half portion of the coil drawn with solid line corresponds to the coil
side lying on the top of a slot, and the dotted line corresponds to the coil side lying in the bottom
layer of another slot. This type of representation is used for double layer winding. For a single
layer winding, the complete coil is represented by a solid line.
Inactive side of a coil : The inactive side of a coil consists of two portions, namely the front end
side and the back end side. In Fig. 3.1 (a), the portion of the conductor which joins the two active
sides and placed around the core, is called the back end side of the coil. The portions which are
used to connect other coils are called front end side. These ends have two leads called as
Fig.3.1 - Winding Coil representation
Active sides
N
S
a) Single turn coil
b) Multi turn coil
Back end
side
Front
end side
A
B
C
D
N
S
SF