• At standstill condition the value of slip is One.
• Slip is defined as the difference between synchronous speed (speed of the stator magnetic field) and the actual speed of the rotor divided by synchronous speed.
• At standstill condition, the rotor is not rotating, so the actual speed of the rotor is zero. 

The slip at standstill can be calculated as follows:

Slip = (synchronous speed - rotor speed) / synchronous speed Slip = (ns - 0) / ns Slip = 1

This means that the rotor is not able to keep up with the rotating magnetic field, and the slip is at its maximum value of 1.

The high slip value results in a low starting torque, which is why induction motors require some kind of external assistance during startup, such as a starting capacitor or a soft starter.