Your Guide to Choosing the Best Brush Grade for Motor/Generator Efficiency

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How to handle a request for a harder or softer carbon brush grade and our carbon motor brushes, ac motor brush.

We often receive requests for a change in brush grade, but it’s important to look at the problem from all angles before making the switch to a hard or softer carbon brush. For instance, you may think a harder brush grade will offer better brush life or prevent excessive dusting. However, oftentimes the carbon brush grade is not the reason for poor performance in the brush circuit. Before proceeding with a change in brush grade, we must understand the application and get to the root cause of the problem to maximize motor/generator efficiency.

Step 1. Gather Information

When a motor OEM manufactures a motor, they engineer it to operate within the parameters of the nameplate. Usually, little consideration is given to the application, environment, ambient outside temperatures, humidity, duty cycle, etc..

Before modifying the brush grade, it is crucial to gather comprehensive information. Below is an extensive list encompassing all the essential information needed to optimize motor/generator efficiency and maximize brush life: 

  1. What is the problem that needs to be resolved by moving to a harder or softer grade?
  2. What is the condition of the brush holders?
  3. What is the condition and design of the springs? What is the spring force?
  4. What is the condition of the contact surface (commutator or slip ring)?
  5. What is the environment like (climate, ambient temperature, humidity)?
  6. What is the application (paper, steel, concrete manufacture, annealing, etc.)?
  7. What type of cooling is used (blower, inside or outside air)?
  8. What is the duty cycle?
  9. What is the load?
  10. How many total brushes are being used?

Step 2. Consult with Experts for Brush Grade Selection

When all this information is taken into consideration, the data can be reviewed and run through a few formulas to determine the proper brush and grade to optimize motor/generator efficiency for your application. It’s possible that the application may call for a different carbon grade. However, the issue could also be related to spring pressure, the numbers of brushes, bad surface conditions, or other factors. Collecting the data above will enable Helwig Carbon engineers to make a recommendation on how to maximize the brush life and performance.

Helwig Carbon also has expert Field Service Representatives that can assist you to diagnose issues and assist with solutions on site.

Please contact us or go here to find your local Field Service Representative.

Michael A. Burke Sr.
Field Service/Sales Representative for Texas, Oklahoma, Arkansas & Louisiana
Helwig Carbon Products Inc.


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