A particularly promising industrial prime mover is a line start permanent magnet synchronous motor (LSPMSM). LSPMSMs, just as other energy receivers, are exposed to the noxious impact of various power quality disturbances. Previous works on this issue have been limited to the effect of voltage harmonics, voltage unbalance and voltage deviation on the motor. This study initiates novel research on the LSPMSM supplied with the voltage containing subharmonics, which involve components with frequencies less than that of the fundamental component. The results of experimental investigations are presented for a factory-made 3-kW LSPMSM. Voltage subharmonics were found to exert an extraordinarily harmful influence on motor under consideration. Subharmonics of values similar to those reported in real power systems were determined to cause unacceptable vibration.