When there is a need for cleaning the contact surfaces of commutators and slip rings with brushes, emery cloth with aluminum oxide is NOT recommended, as conductive abrasive particles will cause arcing and damage to the surface. Many times, stone cleaning, garnet paper and machining are not a convenient, sufficient, or cost-effective option for machines as the priority is to keep the downtime to a minimum. This is when the carbon brush can be designed to clean up the contact surface.

Cuando sea necesario limpiar las superficies de contacto de los colectores y anillos rozantes, NO se recomienda usar tela de esmeril con óxido de aluminio, ya que las partículas abrasivas conductoras pueden causar arcos eléctricos y dañar la superficie. Muchas veces, la limpieza con piedra, el papel granate (Garnett) y el mecanizado no son una opción conveniente, suficiente ni rentable para las máquinas, ya que la prioridad es minimizar el tiempo de parada. En este caso, la escobilla de carbón se puede diseñar para limpiar la superficie de contacto.

This video shows the proper procedure for seating carbon brushes in a DC machine.

This video will walk you through how to check the relative polarity of DC machine interpoles and the armature and correct it if necessary using a simple interpole polarity test.

When working with DC machines, it’s not uncommon to find a customer who runs different products requiring a range of armature current. Unlike other conductors, where lower current is a good thing, carbon brushes are designed for a narrow range of current density. A unique aspect of carbon brush life is that brushes operating at a much lower current density than they are designed for do not last nearly as long as expected.

Al trabajar con máquinas de CC, no es raro encontrar un cliente que fabrica diferentes productos que requieren un rango de corriente de armadura. A diferencia de otros conductores, donde una corriente más baja es algo bueno, las escobillas de carbón están diseñadas con poco margen de densidad de corriente.

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.

This video shows how to adjust the brush neutral position of a DC machine to prevent sparking at the brushes at full load.

This webinar discusses specific procedures to obtain the best possible results when machining & undercutting commutators for DC machines.

A convenient incoming inspection report for basic DC motor conditions and test values.

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.

The paper "DC Motor Testing & Commutation Issues" by Tom Bishop, presented at the EASA Convention 2008, provides a comprehensive guide to testing DC motors and addressing commutation issues. The paper covers various tests to perform during different stages of motor repair, including incoming, post-disassembly, in-process, and final testing. It also discusses the interpretation of DC motor nameplates, testing armatures, commutators, field coils, and interpoles, as well as diagnosing and solving commutation problems.

One of the least understood parts of a DC motor is the commutator. With a little understanding and some helpful tips, commutator life can be maximized.