Question

A 3-phase, 400 V, 50 Hz induction motor runs at 1440 RPM. If the synchronous speed is 1500 RPM, what is the slip?

• A. 2%
• B. 4%
• C. 6%
• D. 8%

Hint:

Slip is critical for torque in induction motors; always use RPM for calculations.

Answer 1

The Correct Option is B

Step 1: Recall slip formula
Slip ($s$) = $\frac{N_s - N_r}{N_s} \times 100$, where $N_s$ is synchronous speed, $N_r$ is rotor speed.
Given: $N_s = 1500$ RPM, $N_r = 1440$ RPM.
Step 2: Substitute values
$s = \frac{1500 - 1440}{1500} \times 100$.
Step 3: Calculate slip
$\Rightarrow s = \frac{60}{1500} \times 100 = 4%$.