Question

A motor has synchronous speed of \(1000\ \text{rpm}\) and runs at \(950\ \text{rpm}\). If the torque at this slip is \(10\ \text{Nm}\). What is the torque if the slip is doubled? (assume low slip region)

• A. \(5\ \text{Nm}\)
• B. \(10\ \text{Nm}\)
• C. \(20\ \text{Nm}\)
• D. \(40\ \text{Nm}\)

Hint:

In the low slip region of an induction motor, torque is directly proportional to slip.

Answer 1

The Correct Option is C

Concept: In an induction motor, in the low slip region, torque is approximately directly proportional to slip. \[ T\propto s \]

Step 1: Initial torque is: \[ T_1=10\ \text{Nm} \]

Step 2: Since slip is doubled: \[ s_2=2s_1 \]

Step 3: In low slip region: \[ \frac{T_2}{T_1}=\frac{s_2}{s_1} \] \[ \frac{T_2}{10}=2 \] \[ T_2=20\ \text{Nm} \] Therefore: \[ \boxed{20\ \text{Nm}} \]