It's interesting that this is a brushed design. In the RC car community, brushless motors are generally regarded as superior, but those of course have the rare earth magnet problem.
Technically the brushes can wear out, although there are claims they are good for 150,000-250,000 miles it seems.
It's technically not a brush but a slip-ring. The design of these motors is very similar to automotive alternators, just scaled up 100x (in terms of power).
Brushes are used everywhere for transmitting electrical current between two parts that have an unlimited relative motion.
Brushes are typically made of graphite mixed with some binder. The graphite conducts the electrical current, but it also acts as a lubricant.
The metallic part that is in contact with the brush is called a slip ring, if it is continuous, like in synchronous motors, or a collector ring if it is segmented, like in DC motors or single-phase motors with brushes.
I've probably taken apart 10 automotive alternators. Every single one had brushes.
yeah I misspoke, I meant to say that it's a brush riding on a slip-ring (continuous contact, no arcing, lasts long) rather than a bunch of contacts in a cylinder (commutator, arcing, wears out).
Slip rings have brushes.
Yes but they wear less than DC brushed motors exactly because it's a slip ring and not a commutator
Because it's the discontinuities in the commutator where the sparks fly (with much help from self-induction of the motor's coils) and erode the ring and brushes.
It's brushless: https://www.evspecifications.com/images/news/6ec9484/additio...
Makes me wonder why they made that choice, if what your parent commenter said is true.
"Brushless DC motors" are good because brushed DC motors are constantly switching polarity, which causes arcing of the brushes, which causes wear. The brushes are not there to energize the rotor; the rotor is just magnets after all. The brushes are there to tell the stator to change polarity.
Brushless DC motors don't arc -- because they switch stator polarity with electronics that sense the position of the rotor without rubbing parts. (They can also fine-tune the stator current spikes to make the motor very efficient over a wide speed range, which brushed DC motors cannot do.) The lack of arcing is more important than the fact that they don't have rotating contact points.
Brushed AC motors have rotating contact points (slip rings) but they don't arc (ideally), so the contact points don't degrade as fast as brushed DC motors do. But they do carry a lot of current because their purpose is to energize the rotor. Brushed AC motors are not ideal, but making an AC motor "brushless" is not nearly as big a win as making a DC motor brushless.
Wait. You're saying DC motors require current that's constantly switching polarity? So they're sort of really AC internally?
Yep. All motors require constantly changing current. The distinction between AC and DC motors is whether you feed the motor externally with current that is already alternating sinusoidally, or whether the motor itself turns external DC into some kind of AC.