Brush Arc Noise
Broadband electromagnetic noise produced by the tiny arcs that form as the brush passes between commutator segments in a brushed DC motor. It spreads both between the lines and over the chassis, shortens the range of a radio receiver and corrupts analogue sensor readings. Suppressing it at the source is the most effective method.
As the brush passes from one segment to the next, the winding current is interrupted and a short arc forms. This arc produces continuous pulses at a repetition rate tied to the motor speed; the steep edges of the pulses cover a wide frequency band.
- Differential suppression: a capacitor connected between the motor terminals reduces the line-to-line component.
- Common-mode suppression: capacitors connected between each motor terminal and the motor body open a short path for the component returning over the chassis.
- Series ferrite: a ferrite bead or small choke placed in series with each terminal forms an LC filter together with the capacitors; it is markedly more effective than a capacitor on its own.
- Layout: the suppression components are mounted on the motor's own terminal end, with the shortest possible connections.
This is why having the receiver and the motor on the same vehicle requires care in radio-controlled crane remote controls. With range complaints, the antenna position and the quality of the chassis connection are checked first, then the motor suppression.
The context in which this term is used: Installation, redundancy and field continuity