As shown in the illustration, which brush holder would be appropriate to use in a bi- directional motor? Illustration EL-0029

Correct Answer: Option D — radial mount

Radial mount brush holders position the carbon brush perpendicular to the commutator or slip ring surface. According to IEEE 45 and rotating machinery design principles, this neutral angle configuration allows the motor to reverse direction without wedging, chipping, or fracturing the brush, unlike directional leading or trailing mounts.