To provide a motor drive system S in which translocation of a current and switching of windings can be integrally performed by using a high-reliability and low-cost semiconductor device.

Regarding phase windings U, V, W, one end is connected to an output terminal of a first inverter 14 and another end is connected to an output terminal of a second inverter 15. Further, one end of each of the phase windings U, V, W is connected to an input terminal of a three-phase full-wave rectifier 16. A short circuit 17 for short-circuiting positive and negative terminals is connected to the three-phase full-wave rectifier 16, and a semiconductor switch 18 is provided in the short circuit 17. By synchronously operating the first and second inverters 14 and 15 in the state where the semiconductor switch 18 is turned off, operation is performed as a motor with a number M of serial conductors watched from between three-phase lines. By operating the second inverter 15 while turning off the first inverter 14 in the state where the semiconductor switch 18 is turned on, operation is performed as a motor with a number √3 M of serial conductors watched from between three-phase lines.