Patent ID: 8659253

Claim:
An electric power steering device for assisting a steering force of a driver of a vehicle with a driving force of a motor comprising: an electric power source for supplying first current; a controller for setting a current instruction value, which provides the driving force of the motor; a plurality of electric power converters for converting the first current from the electric power source to second current corresponding to the current instruction value; a plurality of pairs of windings, each of which correspond to a respective electric power converter, and generates the driving force of the motor when the second current is supplied from the electric power converter to the winding; and a failure detection element for detecting the first current flowing through the electric power converters and the second current flowing through the windings, and for detecting failure of the electric power converters and the windings, wherein the controller reduces the current instruction value to be equal to or smaller than a predetermined instruction value of a normal operation when the failure detection element detects the failure, and wherein, when the failure detection element detects the failure, the controller controls the electric power converter in a normal state based on a reduced current instruction value to supply the second current to a corresponding winding in the normal state.