This paper presents a new stator topology of fractional-slot concentrated-windings permanent-magnet (FSCWPM) machine in order to reduce the electromagnetic vibration. First of all, the space orders and corresponding
frequencies of the lowest order radial force of FSCW-PM machines is studied. A 12-slot/10-pole FSCW-PM machine is used as an example, and its lowest order radial force harmonics are calculated by analytical method and finite element method, respectively. Then, in order to minimize the amplitude of the vibration acceleration, a new stator structure of 12-slot/10-pole machine is designed, by which the amplitude of the lowest order radial force is greatly reduced. Afterwards, the modal and vibration experiments are performed. The result shows that the 2^nd order radial force with 2f0 frequency contributes most to overall vibration. Finally, vibration simulation models of both machines are established, the results show that the machine with unequal teeth design effectively reduce the electromagnetic vibration.