Specifications

27
Solution :From equation 3.11, m = = 3 From equation 3.8, angle between adjacent slots,
â = = 20
0
. From equation 3.10, K
d
= = 0.96
Winding Factor, K
W
: It is defined as the product of pitch factor and distribution factor.
K
W
= K
P
K
d
3.12
Example 3.6 : Find the winding factor for the Example 3.5.
Solution : From equation 3.9, K
P
=
From equation 3.12, K
W
= K
P
K
d
= 0.96 x 0.94 = 0.902
Mechanical and Electrical degrees: Mechanical degree, θ
md
is used for accounting the
angle between two points on a circle/round object based on their mechanical or physical
placement. Fig. 3.4 (a) shows four points A, B, C, and D marked around a circle. Taking point
A as reference, ie., as 0
0
, point C is located exactly opposite to point A and is marked as 180
mechanical degree or simply 180
0
degrees. In between points A and C, points B and D are
marked as 90
0
and 270
0
respectively. Point A is also marked as 360
0
, as it is the same point as
the reference point, reached after going around circle once.
Fig.3.4 - Mechanical and Electrical Degrees
Electrical degree, q
ed
is used for accounting the angle between two points in rotating electrical
machines. Since all electrical machines operate with the help of magnetic fields, the electrical
degree is used with reference to the polarity of the magnetic field. Consider a two pole machine,
as shown in Fig. 3.4 (b). Point A is exactly under the North pole field and is selected as reference
point with 0
0
. Point C is under the South pole and magnetically opposite to North pole. It is
marked as 180
0
ed
or 180
0
e. After one encircling, point A is reached and marked as 360
0
ed
or
360
0
e. Fig. 3.4 (b) is identical to Fig. 3.4 (a), for a two pole machine.
A
B
C
D
0
90
180
270
(a)
A
B
C
D
0
90
180
270
S
N
A
B
C
D
0
180
360
540
N2
N1
S1
S2
(b) (c)
360 360
720
36
3x4
180
s
p
180
36
4
=