Patent ID: 8598826

Claim:
A control system for an electric motor to which electric power is supplied from a DC power supply via a three-phase inverter, the three-phase inverter including switch units respectively provided on a positive side and a negative side of arms corresponding to respective phases, each switch unit including a switching element and a reflux diode connected in parallel thereto, comprising: a phase current detection unit including three sensors for detecting phase currents which flow between the inverter and the electric motor; a DC component acquiring unit for acquiring DC components of the respective phase currents; and a short-circuiting determination unit for determining that a short-circuit failure occurs in the inverter when at least two of the DC components of the three phase currents acquired by the DC component acquiring unit exceeds a threshold, wherein the short-circuiting determination unit determines that the short-circuit failure occurs in the inverter when all the DC components of the three phase currents exceed the threshold, and determines not only that the short-circuit failure occurs in the inverter but also that one of the sensors making up the phase current detection unit fails when two of the DC components of the three phase currents exceed the threshold.