Patent ID: 8248010

Claim:
A motor driving device comprising: a motor including a plurality of winding sets having windings corresponding to a plurality of phases; an inverter unit provided for each of the winding sets and configured to supply a current to the windings, the inverter unit including a plurality of switching elements including switching element pairs respectively corresponding to the phases of the windings, each of the switching element pairs including a high potential-side switching element on a high potential side and a low potential-side switching element on a low potential side; a switching unit configured to switch each of the switching elements between on and off; a voltage application unit configured to apply a voltage to the windings without passing through the inverter unit; a power voltage detection unit configured to detect a power voltage between the inverter unit and a power supply; a terminal voltage detection unit configured to detect a terminal voltage at a contact between each of the switching elements and corresponding one of the windings; and a control unit including a rotation control unit, a first failure detection unit, and a second failure detection unit, wherein the rotation control unit is configured to control the switching unit to switch each of the switching elements between on and off to control rotation of the motor, the first failure detection unit is configured to detect a short circuit failure in the switching elements based on the terminal voltage and the power voltage before the rotation control unit starts control of the rotation of the motor, and the second failure detection unit is configured such that, before the rotation control unit starts control of the rotation of the motor and when the first failure detection unit does not detect a failure in the switching elements and in a condition where the switching unit is caused to switch at least one of the high potential-side switching element and the low potential-side switching element on and subsequently switch all the switching elements off, the second failure detection unit determines whether the switching unit is incapable of rendering the switching element non-conductive to detect a short circuit failure in the switching unit based on the terminal voltage and the power voltage.