General guidance for performing brush seating or comutator reprofiling in the field.

Orientación general para realizar el ajuste del asiento de las escobillas o del conmutador en el campo.

Ever run across brush arcing or vexing commutation issues? This paper, presented at the 2013 EASA Convention, provides a approach to analyzing brush and commutation problems and failures.

There are times when a DC motor or generator experiences a catastrophic failure and the customer wants to know why it happened. One type of failure that seems to stimulate lively conversation is when the failure involves dramatic damage to the brushholders and commutator. The term "flashover" describes the appearance of the failure; the very name conveys an accurate mental image of the failure. The questions that arise next are predictable: "What caused this?" and "What can be done to prevent a recurrence?" Or, if the motor was recently repaired: "What did you do to my motor to cause this?!" The purpose of this article is to help you answer those questions.

When servicing DC motors, one of the many tests we do to determine the condition of the commutator is to check it for loose bars. We check for loose bars by lightly tapping the face of the commutator with a very small hammer. Then we check for suspicious sounds and movement or vibration of the bars as they're struck. A loose bar will have a dull thud while tight bars will have more of a crisp "peck." You should not feel any movement of the bar with respect to adjacent bars. If the commutator is molded or riveted,it is not repairable and it should be replaced. However, V-ring commutators can be repaired.