Simple Q about induction motor

[aabbddlah]

hello

i v got a small question about induction motors


why does the steady state torqe is equal to zero when rotor speed is equal to 314 rad/s? and
why when rotor speed is for example is equal to 100 , torque maintain a higher positive value

many thanks

 

[Bob S]

Induction motors have a copper busbar cage (called a squirrel cage) embedded in the rotor laminations. The torque is created by the stator field interacting with the field created by the currents in the squirrel cage. No currents are generated in the squirrel cage when the rotor RPM is synchronous with the excitation field in the stator. So a 4-pole induction motor has no torque at 1500 RPM (50 Hz), but a lot at 1450 RPM.
Bob S

 

[oswaler]

Hi there,

Thank you for your question about induction motors. The steady state torque is equal to zero when the rotor speed is equal to 314 rad/s because at this speed, the rotor is rotating at synchronous speed with the magnetic field of the stator. This means that the rotor and stator magnetic fields are perfectly aligned, resulting in no torque being produced.

On the other hand, when the rotor speed is lower, such as 100 rad/s, the rotor is rotating at a speed lower than synchronous speed. This causes a difference in speed between the rotor and stator magnetic fields, resulting in a positive torque being produced to try to align the two fields.

I hope this helps to answer your question. If you have any further questions, please let me know. Thank you.