As industrial technology continues to evolve, synchronous machines powered by inverters are widely implemented to provide enhanced control performance. However, the inverter-fed systems can lead to asymmetries in the three-phase voltages, generating common-mode voltage (CMV) in machines with Y-winding connections configuration. Influenced by the parasitic capacitive effects between the internal conductors of the machine, the CMV results in a potential difference between the shaft and the housing, known as the common-mode shaft voltage (CMSV). When the CMSV exceeds a certain threshold, it can cause the lubricating film of the bearings to break down. To mitigate the risk of bearing failure due to the CMSV, this paper proposes a method for extending stator length, with the advantages of simpler and more cost-effective. This paper first presents the mechanism and mathematical model of CMSV generation, followed by an analysis of potential suppression measures. Furthermore, a method of extending the stator lamination length to reduce the coupling capacitance between the stator windings and the rotor is proposed, thereby achieving suppression of shaft voltage. Finally, a three-dimensional finite element analysis (3D-FEA) software is used to analyze and evaluate the model with different degrees of extending the axial length of the stator or rotor lamination and the machine with different stator inner diameter to axial length ratios. The longer the extension of the stator lamination length, the greater the suppression capability for CMSV. For machines with a larger stator inner diameter to axial length ratio, this method exhibits a more pronounced effect on attenuating the CMSV. Conversely, extending the axial length of the rotor significantly increases the CMSV.