Correct Answer - Option 4 :
2.0
Concept:
The ratio between the starting torque to full load torque is given by:
\(\frac{{{T}_{st}}}{{{T}_{fl}}}={{s}_{fl}}\times {{\left( \frac{{{I}_{st}}}{{{I}_{fl}}} \right)}^{2}}\)
Where Tst is the starting torque
Tfl is the full load torque
sfl is the slip at full load
Ist is the starting current
Ifl is the rated current
Calculation:
The starting current of a 3-ϕ induction motor is 3 times the rated current. i.e.
Ist = 5 Ifl
Full load slip (sfl) = 8 %
\(\frac{{{T}_{st}}}{{{T}_{fl}}}={0.08}\times {{\left( \frac{{5}}{{1}} \right)}^{2}}\)
= 2.0