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