In this paper, a new diagnostic mean is introduced for accurate, reliable, and effective diagnosis of faults in delta-connected induction motors. This mean is the zero-sequence stator current spectrum. The study is carried out with analytical calculations and finite-element method simulations. Most common faults are examined for a 4-kW cage induction motor. The analysis will reveal that the proposed mean is able to successfully identify the static eccentricity fault, even in induction motors which produce principal slot harmonics, the broken bar fault, the unbalanced voltage supply, and the stator interturn short-circuit. It will also be shown that through the proposed method, it is possible to distinguish the interturn short-circuit from the unbalanced voltage supply.