A threephase Yconnected ac machine is initially operating un

A three-phase Y-connected ac machine is initially operating under balanced three-phase conditions when one of the phase windings becomes open-circuited. Because there is no neutral connection on the winding, this requires that the currents in the remaining two windings become equal and opposite. Under this condition, calculate the relative magnitudes of the resultant positive- and negative-traveling mmf waves.

Solution

Under this condition, the mmf wave is equivalent to that of a single-phase
motor and hence the positive- and negative-traveling mmf waves will be of equal
magnitude.