Noise Reduction of the DC Motor for the Electrical Power Steering by Short Circuit Wires for Symmetrical Position

The market of the electrical power steering is expanding rapidly because of its fuel efficiency. The DC motor is generally used in this system, whose noise reduction is demanded. The DC motor has some dispersion in contact number of segments or contact resistance between the brush and the commutator. When these conditions are different with plural brushes, currents in armature coils are in asymmetrical distribution and the unbalanced magnetic pull occurs in radial direction.We measured the radial force and currents in armature coils with the developed experimental apparatus that can also set up the eccentricity of rotor to stator. In this paper, we investigated the factor and the process of the radial force generated in the DC motor. Then we propose short circuit wires for symmetrical position that makes winding current symmetrical and realizes the noise reduction.