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Topic: Driving a Car Alternator as a Motor (Read 7729 times) previous topic - next topic


I am hellbent on turning my spare alternator into a motor and using my Arduino Uno to drive it. I guess I could get an already-available controller, but I want to play with how much voltage I can put through it, etc. I've been exploring this idea for a few days and this is how far I got in my search.

The rotor takes 12 volts DC. I have sweet access to the terminals of the stator. I have some high-capacity MOSFETs on the way. The Arduino should have the PMW capabilities to handle this, right? (I'm told that I need synced PWM channels and that Arduino has them. I don't know yet what exactly this means, but if I need them and the thing has then than it's all good, right?)

I can write the code, but I need detailed info to do it. I could also use a list of additional components that I will need and an explanation as to what exactly they do. 

Thanks in advance.


I suspect that an alternator (minus its rectifier) would behave like a brushless motor - except that it uses an electromagnet rather than a permanent magnet.

I also suspect that brushless motors need phased power rather than simple PWM.

Two or three hours spent thinking and reading documentation solves most programming problems.


Car alternators are 3 phase with a full wave diode bridge to produce the DC.
The only way to run one as a motor is to supply 3 phase AC at whatever frequency you want the motor to run at.
Its possible but a lot of work, and needs specialised electronics.


You can run an alternator as a motor by connecting the three wires from the stator to an relative inexpensive sensorless ESC for BLDC (electronic speed control for brushless DC). I have done this, and it works. However, because it's sensorless, the motor can't start under load and looses synchronization if your apply too much load to it while it's running. I would speculate that in order to make good use of an alternator as a motor (BLDC), you would need to add sensors to it and use a BLDC sensored controller. The supply voltage would probably need to be at least 24v, but ideally a lot more, like 48 - 96V. An alternator easily generates more than a 100V, without regulation. Also the controller needs to be able to supply a lot of current, probably at least 100A.
You should not supply the rotor with 12V, but instead something like 6V, or better use PWM regulation. With a regulated supply to the rotor you can get "electric gears". Hi power to the rotor equals hi torque and low rpm, and low power equals hi rpm and low torque.

Check this link: http://www.rcgroups.com/forums/showthread.php?t=905411

Good luck,

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