Permanent magnet synchronous motors (PMSMs) are widely used for many purposes because of their efficiency and energy density. Because of their increased use, they require improved efficiency, lower noise, and fewer vibrations. Static eccentricity and roundness degradation generate a magnetic unbalance in the magnetic gap and cause a low-order harmonic electromagnetic force and cogging torque that creates noise and vibration. Since multi-three-phase PMSMs can individually control the phase current of each group, it is possible to reduce magnetic unbalance in the magnetic gap; however, to control the phase current of each group, the magnetic unbalance must be detected. In this study, we use the harmonics of no-load stator voltages to theoretically and analytically detect static eccentricity on multi-three-phase PMSMs.