Abstract: An electric power collection and distribution ring includes first to third bus rings configured to collect and distribute electric power from and to winding wires of a plurality of phases. The first to third bus rings include first to third annular conductor parts, respectively, and first to third feeding terminal parts, respectively, configured to feed electric power to the first to third annular conductor parts, respectively. The second feeding terminal part projects toward another side in an axial direction of the first to the third annular conductor parts without projecting toward the one side in the diameter direction than the first annular conductor part. The third feeding terminal part projects toward the another side in the axial direction of the first to the third annular conductor parts without projecting toward the one side in the diameter direction than the second annular conductor part.

Abstract: To make it possible to avoid an unstable state with a simple configuration even one of the phases of the motor fails. A motor drive system in accordance with the present invention includes a motor to which a plurality of phase coils of five phases or more are connected in a star connection, an inverter connected to one end of each of the phase coils, the inverter being configured to convert a DC power into an AC power and supply the AC power to each phase of the motor, a power relay disposed at another end of each of the phase coils, the power relay being configured so as to be able to cut off a supply power to at least one phase coil among the plurality of phase coils of the motor by using a plurality of contact points interposed between the star-connected coils, and a control unit that generates a control signal for the inverter and thereby controls driving of the motor.