To study the effect of changing the core area of the stator on the iron loss in the fractional slot concentrated winding (FSCW) permanent magnet (PM) synchronous machine, two sets of research schemes are proposed for the stator slots, which are based on the 8-pole 9-slot PM machine, including only increasing integer multiple of the stator slot width and the number of stator slots without changing the stator slot size by finite element analysis (FEA). Then, the principle of iron loss calculation and detailed comparisons of the performance characteristics of the machines are presented that include important issues such as the harmonic of back EMF, stator yoke flux density, iron loss and eddy current losses in the magnets. The analysis results show that an optimization is carried out to determine the width of stator slot, which reduces the iron loss, magnet eddy current loss and harmonic content without significant decreases in the performance. It is found that properly increasing the width of the stator slot to reduce the influence of iron loss is better than increasing the number of stator slots of the machine. In addition, the torque ripple is more affected by the number of slots in the motor stator than by changing the area of stator slots. The filtering algorithm is applied to the magnetic flux leakage signal collected in the experiment. The results show that the filtering algorithm can filter the noise well.