Rotating electric machine control device and electric power steering device using the same

1. A rotating electric machine control device for controlling a rotating electric machine having at least one winding set, which includes a plurality of windings for a plurality of phases respectively, the rotating electric machine control device comprising:

at least one inverter having an upper arm element connected to a high-potential side and a lower arm element connected to a low-potential side of the upper arm element, and converting an electric power of the rotating electric machine;

a terminal voltage detection device detecting a terminal voltage of each phase of a respective winding;

a resistor connecting each phase of a respective winding and a positive side of a power supply; and

a control device having a signal generation device that generates a control signal for controlling an on and off operation of the upper arm element and the lower arm element, and a failure detection device that detects a failure based on a sum of the terminal voltage in all of the phases when all of the control signals relating to the upper arm element and the lower arm element represents an off command, and a rotation speed of the rotating electric machine is lower than a predetermined rotation speed threshold.

2. The rotating electric machine control device according to claim 1 , further comprising:

a rotational angle sensor detecting a rotational angle of the rotating electric machine, wherein:

the failure detection device determines whether the rotation speed is lower than the rotation speed threshold, based on the rotation speed calculated by the rotational angle.

3. The rotating electric machine control device according to claim 2 , wherein:

in a case where the rotational angle sensor is normal, the failure detection device determines whether the rotation speed is lower than the rotation speed threshold, based on the rotation speed calculated by the rotation angle; and

in a case where the rotational angle sensor is not normal, the failure detection device estimates that the rotation speed is lower than the rotation speed threshold when an amplitude of the terminal voltage is less than a predetermined determination feasibility threshold.

4. The rotating electric machine control device according to claim 3 , wherein:

the at least one winding set includes a plurality of winding sets;

the at least one inverter includes a plurality of inverters, each of which corresponds to one of the winding sets; and

in a case where the rotational angle sensor is not normal, and the amplitude of the terminal voltage is normal according to a comparison among the amplitudes of the terminal voltages calculated for the inverters respectively, the failure detection device estimates that the rotation speed is less than the rotation speed threshold when the amplitude of the terminal voltage is less than the determination feasibility threshold.

5. The rotating electric machine control device according to claim 1 , further comprising:

a bus voltage detection device detecting a bus voltage of a positive-side bus connecting a high-potential side of the upper arm element and the positive-side of the power supply, wherein:

the failure detection device detects a failure based on the bus voltage and a sum of the terminal voltages of all the phases.

6. An electric power steering device comprising:

the rotating electric machine control device according to claim 1 ; and

the rotating electric machine outputting an assisting torque to assist a steering operation of a driver.