In an inverter system including of an electric-power converter and an ac rotating machine, over-voltage generated in the ac rotating machine is controlled by a low-cost system configuration. The system includes: an electric-power converter; a three-phase ac rotating machine; and a four-core non-coaxial cable, having a ground line and three-phase electric-power supplying lines, connecting the electric-power converter to the three-phase ac rotating machine. One or two capacitors are connected between the ground line and one or two of the electric-power supplying lines, at electric-power supplying terminals on the rotating machine, so that respective capacitances between the three-phase electric-power supplying lines and the ground line are approximately equal to each other.
