# The starting current of an induction motor is five times the full load current while the full load slip is 8%. Find the ratio of starting torque to fu

158 views
in General
closed
The starting current of an induction motor is five times the full load current while the full load slip is 8%. Find the ratio of starting torque to full load torque.
1. 8.0
2. 4.0
3. 0.6
4. 2.0

by (35.4k points)
selected

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