Synchronous electric motor control device, integrated electric motor system, pump system, and positioning system

A synchronous electric motor control device equipped with a synchronous electric motor in which three-phase stator coils are Y-connected, a detection unit that detects the neutral-point potential, which is the potential at the Y connection point, and an inverter that drives the synchronous electric motor, the inverter being used to control the synchronous electric motor. This synchronous electric motor control device has a measurement mode in which the neutral-point potential is detected while alternating current is supplied to the synchronous electric motor. The synchronous electric motor control device controls the synchronous electric motor on the basis of the neutral-point potential value detected in the measurement mode.