In this paper no-load and full-load performance of Permanent Magnet Vernier Generators (PMVGs) is investigated in fully-aligned condition and under different types of mechanical faults. The studied mechanical faults are Static Eccentricity (SE), Dynamic Eccentricity (DE), Inclined Rotor (IR), and Run-out (RO). Furthermore, an analytical model is developed to calculate the permeance of the air-gap and the induced voltages in the health machine and under studied mechanical faults. Then, 2-D and 3-D time stepping finite element method is utilized for performance evaluation of the generator. Some discussions are made on the quality of induced voltages, torque ripples, variations of axial and radial forces and the output power of the generator under the mechanical faults considering resistive, inductive and capacitive loads connected to the terminals of the generator. Finally, the performance of an outer rotor conventional permanent magnet generator (CPMG), considering constant dimensions, constant PM, copper and iron usage is compared with the studied PMVG. The performance of two generators is studied in fully-aligned condition as well as under SE and DE.