The manufacturing errors of machine tools are usually due to the imperfect of bearings, stiffness of spindle, assembly errors, and so on. In addition, the rotor eccentricity of the permanent magnet (PM) machine affects to
the constant torque and speed characteristic of mechanical loads. The errors due to rotor eccentricity is caused by manufacturing process and rotor eccentricity generate unbalanced magnetic force (UMF). The sources of
UMF are generated by the interaction between the rotor magnets and the stator core. Firstly, we suggested that the characteristic analysis results due to rotor eccentricity are calculated by using finite-element (FE) analysis. Moreover, we proposed experimental set to measure the UMF on the PM machines. Finally, we verified the validity of the proposed UMF measurement system by comparison with the measured results and simulation results due to the rotor eccentricity in the PM machine.