Page 133 - Handbook of Electrical Engineering

INDUCTION MOTORS 115

Table 5.2. Per-unit reactances and starting-to-full-load torque ratio for LV two-pole
motors
Rated power Slip (pu) X 1 X 20 X 21 X M T s /T n
(kW)
11 0.0433 0.0840 0.114 0.0531 2.317 1.50
15 0.0355 0.0833 0.124 0.0528 2.503 1.61
22 0.0282 0.0825 0.137 0.0527 2.752 1.73
30 0.0237 0.0819 0.147 0.0529 2.970 1.80
37 0.0216 0.0815 0.153 0.0532 3.126 1.84
45 0.0191 0.0812 0.159 0.0536 3.278 1.86
55 0.0173 0.0809 0.165 0.0541 3.442 1.86
75 0.0150 0.0804 0.173 0.0551 3.708 1.85
90 0.0138 0.0802 0.178 0.0558 3.874 1.83
110 0.0126 0.0799 0.182 0.0567 4.064 1.80
132 0.0117 0.0797 0.186 0.0576 4.244 1.76
160 0.0108 0.0795 0.189 0.0587 4.442 1.70
200 0.00995 0.0793 0.193 0.0601 4.682 1.63
250 0.00917 0.0791 0.196 0.0617 4.934 1.55
315 0.00846 0.0790 0.198 0.0635 5.207 1.45

Table 5.3. Per-unit resistances and starting-to-full-load current ratio for LV four-pole motors
Rated power Slip (pu) R 1 R 20 R 21 R c I s /I n
(kW)

11 0.0527 0.0405 0.0379 0.0497 14.92 6.01
15 0.0436 0.0361 0.0319 0.0488 16.06 6.03
22 0.0352 0.0311 0.0261 0.0478 17.41 6.06
30 0.0299 0.0275 0.0225 0.0471 18.43 6.08
37 0.0270 0.0252 0.0204 0.0468 19.07 6.10
45 0.0246 0.0232 0.0187 0.0464 19.63 6.13
55 0.0225 0.0213 0.0172 0.0462 20.16 6.16
75 0.0197 0.0186 0.0152 0.0458 20.86 6.22
90 0.0183 0.0171 0.0142 0.0456 21.22 6.26
110 0.0170 0.0156 0.0132 0.0455 21.55 6.31
132 0.0159 0.0144 0.0124 0.0454 21.79 6.37
160 0.0148 0.0131 0.0117 0.0453 21.99 6.43
200 0.0138 0.0118 0.0109 0.0453 22.14 6.52
250 0.0129 0.0106 0.0102 0.0453 22.21 6.62
315 0.0121 0.00942 0.00965 0.0454 22.19 6.74

represented by a series circuit of the R + jX type. This approach can be used to represent the deep-bar
effect in the rotor of an induction motor. It has the effect of splitting the rotor bars into a set of outer
bars and a set of inner bars, both sets then being independent of each other. In addition the resistances
become simple reciprocal functions of slip, whilst the inductive reactances remain constant as the
slip varies.
Let the outer bars be represented by the series branch R 22 /s + jX 22 and the inner bars by the
branch R 33 /s + jX ,where s is the slip. Let the sum of the two branches be R 23 /s + jX .Itis
23
33