Class: BEE2-A
Time Allowed: 10 mins
Maximum Points: 10
Reg. No:
QUIZ EIGHT - SOLUTION
NOTE: Please draw labelled circuit diagrams where appropriate, show complete calculations, and reasoning
to get maximum marks.
1. A 3 phase, 10hp, 208V, 60Hz, 6 poles wound rotor induction machine has a stator to rotor turns ratio of
1:0.5 and both stator and rotor are connected in Y.The motor speed is 1140 rpm. Determine:
a. The operating slip. [2]
b. The voltage induced in the rotor per phase. [3]
c. The frequency of the induced voltage. [1]
d. The rpm of the rotor field with respect to the rotor. [2]
e. The rpm of the rotor field with respect to the stator. [2]
SOLUTION
a. nsync =120fe
P=120×60
6= 1200rpm
s=nsync−nm
nsync
×100% = 1200−1140
1200 ×100% = 0.05
b. E2=sE2o=sE1
a
E2= 0.05 ×1
2×208
√3= 3V
c. fr=sfe= 0.05 ×60 = 3Hz
d. nrotorf ield =nstatorf ield =nsync = 1200rpm
nrotor =nm= 1140rpm
→The rpm of the rotor field w.r.t. rotor = 1200 - 1140 = 60 rpm
e. nrotorf ield = 1200rpm, nstator = 0rpm [Stator is stationary].
→The rpm of the rotor field w.r.t. stator = 1200 - 0 = 1200 rpm
1
docsity.com