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Magnet Energization in Brushless Motors

This article was originally published in RC Driver’s September 2015 issue.
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Hey Tony. How are the magnets on a brushless motor energized in sequence?
Kieran Sweaney, Bellingham, WA


Hiya Kieran, This is an article in itself so I’ll give a quick explanation. Let me start by saying that the magnets in a brushless motor are no longer attached to the can, like a brushed motor. They are instead wrapped around the central rotor while the wire coils are attached to the can. So in brushless motors, the magnets are not being energized anymore (like a brushed motor) … the coils are. The battery sends juice to the ESC which sends three sepa- rate pulses (one for each wire) to the mag- netic poles (or wire coils) that are fixed around the magnetic rotor. These pulses ‘pulse’ in a way that rotates the rotor. If more juice is introduced (for instance, you pulling the throttle more), the timing or fre- quency of these pulses is increased, spin- ning the rotor faster. If you let off the throttle (to slow down), the timing or frequency of these pulses is decreased. I hope that helps you out. —Tony

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