When a rotor is in a stationary mode, then the frequency of the current generated by that rotor will; be similar to supply current. This frequency is completely dependent on slip speed or also known as relative speed. This happens when that rotor itself starts rotating. Its equation is depicted by,
As per this, whatever be the value of slip, both stat or current and rotor current are efficient enough to produce a magnetic field which sinusoidally distributes at constant speed and magnitude.