An induction motor always runs at a speed less than synchronous speed because the rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor to rotate, but due to the lagging of flux current in the rotor with flux current in the stator, the rotor will never reach
Keeping this in consideration, what happens when the speed of an induction motor reaches the synchronous speed?
2)If you drive it by external force to gain synchronous speed, or won't generate torque. If you mean that rotor runs at synchronous speed as the field of the stator , this will cause that slip to be zero , then there will be no torque generated in rotor , then rotor will be at standstill.
What is the difference between synchronous speed and actual speed?
Induction motor with squirrel cage rotor has two different speeds. The synchronous speed refers to the stator rotating magnetic field, which depends on the number of poles and frequency. The other speed is the rotor's. The rotor speed will be always slower than the stator speed, we call it slip.