| 摘要 |
PURPOSE:To prevent a fan and the exciting force of an armature from resonating through spark by arranging the center of one brush in the position of from -10% to +10% of the center between commutator segments, when the center of the outer brush is placed in the center of a commutator segment. CONSTITUTION:The number of segments of a commutator 1 is 23, and the brush space C between brushes 2a and 2b is 3.5 times as much as a commutator segment pitch. In this manner, the point of time, when sparks fly in the brush 2a, and the same, when sparks fly in the brush 2b, differ from each other by 0.5 segment pitch, which is the half of usual 1 segment pitch. Consequently, the frequency of the exciting force of an armature through spark is twice as much as usual one and said exciting force is the half of usual force so that resonance with a fan is eliminated and noise can be reduced.
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