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This thread is privately moderated by phil alvirez, who may elect to delete unwanted replies.
Jan 22, 2012, 08:50 PM
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esc for brushed or brushless motors


i asked Lucien Miller, of innov8tive designs, what's the difference bet escs for brushed or brushless motors. he said:
Brushed ESC's require only one transistor typically to turn the power on and off between the battery and motor. In a brushed motor, the commutation happens internally in the motor, so you simply need to feed it voltage. If you have a 12 volt battery and hook it directly to the motor, it will run at a certain speed. If you put an ESC in between the motor and ESC, and have the ESC operate so that it turns on and off quickly, normally around 2000 or 3000 times per second, you can vary the amount of power that reaches the motor.

If the ESC is on for half of the time and off for half of the time during each cycle, the average effective voltage that the motor gets is 6 volts, and you have half throttle. If it is on for 1/4 of the time and off for 3/4 of the time, you effectively get 3 volts, and you have 1/4 throttle.

In brushless motors, there is no commutator, so that has to be done in the speed controller. Also, brushless motors are usually 3 phase motors, and that is why they have 3 wires. A brushless speed controller usually requires a minimum of 6 transistors, 3 N-channel and 3 P-channel. When the motor runs at full throttle, the ESC sends out pulses in turn to phase A, then Phase B and finally Phase C before repeating the process. Each time you go through one cycle of all 3 phases, the motor rotates through 2 magnets in the housing. This process repeats over and over again as the motor spins. For less than 100% throttle, the ESC chops up each of the phase pulses into smaller pulses, just like the brushed ESC does, and this provided reduced effective voltage to the motor and it slows down.

actually, the process is very complicated and would take several pages to fully explain, but that is the basic difference between brushed and brushless ESC's.
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