If the commutator is not mechanically true, what issue is most likely?

• A. Brush chatter and erratic commutation
• B. Increased efficiency
• C. Reduced noise
• D. Faster speed

Answer: (A)

When the commutator isn’t true, its surface isn’t a perfect cylinder. As the rotor turns, the contact between a brush and a commutator segment becomes uneven, causing the point of contact and the current reversal to drift. That leads to inconsistent timing and pressure at the brush, producing sparks, vibration, and irregular electrical contact. The most likely outcome is brush chatter and erratic commutation, with noticeable noise, vibration, and wear.

The other options describe improvements that wouldn’t result from a out-of-true commutator. In practice, mis-truing tends to hurt performance by increasing wear and noise and often reducing efficiency or smooth speed, not improving them.