What would be the current of the 3-ph AC motor, if it lost one feeding phase?
The load, efficienty and power factor (theoreticly would say stay) constant.
Power factor, efficiency and a few other things do not stay constant. So your question cannot be answered, really.
But, of course, if it is some kind of example or test used in school, you can always calculate what current the three impedances pass. Wye or delta? Hint: does it really matter?