Page 108 - Industrial Power Engineering and Applications Handbook

Starting and control of slip-ring induction motors 5/89

C

T

35 dl Id2 /d3 d4 d

d5
d2

d4

d3
I
C
uj
d
d2

dl
‘Contactors connected in A to reduce their size

Figure 5.6(b) Power and schematic diagram for a five-step stator-rotor starter

Once p is known, the resistance value for each step Example 5.3
can be determined. In the above case, the slip S,,, Consider a rotor resistance unit with five sections (total number
corresponds to the slip at the operating point ofthe torque of steps is Six). Then in the previous example (Figure 5.4),
or current curve, where the desired torque T,,, or current considering Tst as 200% and the corresponding slip Sm, as
roughly 14% then
I,,, occurs. This can be obtained from the torque and
current curves available from the motor manufacturer - 0.09
(Figure 5.4). 21 - -
0.14