Using high-speed camera, we have been doing some experiments to clarify the mechanism of the commutation spark generation from the image aspect in universal motor. Previously we mentioned about the cases of single and plural number of sparks generation at single commutator segment This time, we took pictures of all the sparks generated during a single-rotation of the motor and examined sparks generation distribution and their positions of the brush. As a result, we observed that the closer the position to the side where the brush and the armature coil are connected the more sparks are generated. Also we measured the voltage between brush and commutator segment.
