an investigation of dual stator winding induction machines

L
2
2
S πµ 0rl
⎛ 3P2
N s2
⎞ 2πµ
0rl
2
ij = − ⎜ ⎟ = − N
2
s2
(3.49)
54P2
g 0 ⎝ S ⎠ 3g
0
where, i , j = X , Y,
Z and i ≠ j .
3.5 Calculation of Rotor Inductances
A method to adequately model a squirrel cage rotor has been set forth in [1.10, 2.3].
The squirrel cage rotor with n (even or odd) bars and two end rings to short circuit all the
bars together is considered as n identical magnetically coupled circuits. Each circuit is
composed of two adjunct rotor bars and segments of the end rings connect two adjacent
bars together at both ends of the bars. Each bar and end ring segment of the rotor loop is
equivalently represented by a serial connection of a resistor and an inductor as shown in
Figure 3.5.
The resistance and the inductance of the rotor bar are represented by r b and l b
respectively; the resistance and inductance of the partial end winding in the rotor loop are
represented by r e and l e respectively. Three rotor loops are shown in Figure 3.5 and the
current flowing through the rotor loops are represented by i k −1,
i k and i k + 1 respectively.
Since every rotor loop is treated as an independent phase, a healthy cage rotor having n
rotor bars becomes a n phases balanced system.
The turn function of th
i rotor loop is shown in Figure 3.6 (a). Since a constant air gap
length is considered in this chapter, the winding function of the th
i rotor loop can be
easily found with Figure 3.6 (b).
104