D.C. Motors

Misshapen or pitted commutator segments or improper brush contact can cause excessive vibration in D.C. motors with the commutator. The frequency will be at the segment pass frequency, which is the number of commutator segments times the RPM.

If the 360 Hz peak in the vibration spectrum rises significantly, the likely cause is probably open circuited field windings, loose electrical connections, or malfunctioning SCRs.