I notice that your precious-metal motors and graphite commutated motors have the same terminal resistance for the same motor. That seems unlikely to me. What is a typical resistance of the two brushes when going from precious metal (which is basically zero) to graphite? Some companies model this as a series resistance and others knock off some voltage. What does Maxon do? @ Ask The Experts

Motors and Motion Control Q&A

I notice that your precious-metal motors and graphite commutated motors have the same terminal resistance for the same motor. That seems unlikely to me. What is a typical resistance of the two brushes when going from precious metal (which is basically zero) to graphite? Some companies model this as a series resistance and others knock off some voltage. What does Maxon do?

Answered July 30th, 2010 by Expert: Paul McGrath

Our motors are built with either precious-metal brushes or graphite brushes. We do offer some of our motors in specific sizes in both versions. On the smaller motors, the terminal resistance can be the same for both precious metal and graphite. On the larger motors, the resistance of the graphite brushes might be slightly higher. It is also important to note that the contact resistance of the graphite brushes changes depending on load. We list our specs based on 25°C ambient.

Paul McGrath

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