ASSIGNMENT 2
UNIT IV – DESIGN OF INDUCTION MOTORS
1) Estimate the main dimensions of 70HP, 400V, 3phase, 50 Hz, star connected 8pole
induction motor for which Bav=0.51 Wb/m2 and ac=30000 ac/m. Take efficiency=92%
and power factor=0.9. Assume Pole length=pole pitch. Estimate the number of stator
conductors are connected in 4 parallel paths. Choose a suitable number of conductors per
slot, so that the slot loading does not excedd 350 amp.conductor.
Answers: D=0.382m, L=0.1491m, Zs=2304conductors, Zss=32, Ss=72.
2) A 20KW, 400V, 3phase, 4pole, 50Hz, 1500rpm, delta connected slip ring induction
motor has Bav=0.5 wb/m2 , ac=26000ac/m, efficiency=0.82, p.f=0.8. Determine the main
dimensions for obtaining best power factor.
Answers: D=0.226m & L=0.175m
3) A415V,3 phase, 50Hz, 6 pole delta connected induction motor has Bav=0.5wb/m2 and
ac=24000ac/m. The stator core lengths are 0.275m and 0.15m respectively. Find the
output of the machine if the full load efficiency and power factor are 0.88 and 0.89
respectively. Determine the number of stator slots, conductor per slot and length of
airgap.
Answers: Q=18.75KW, Ss=54 & lg=0.6mm