Transient Behavior of the Resultant Airgap Field During Run-Up of an Induction Motor

The present paper deals with the transient behavior of the main airgap field of an induction machine starting from rest. This is often visualized as a revolving field having constant steady-state speed and direction. In this paper the results obtained show the complex movement of the field as a space vector. It is shown that the transient airgap field has a variable speed and amplitude and sometimes moves in the reverse direction. The results are used to explain the occurrence of transient torque reversals and motor operation over synchronous speed.