Alternator as motor during acceleration?

[Piotrsko]

Sometimes I'm careless, other times I just like to annoy people

[Tahoe_Hybrid]

Originally Posted by serialk11r

Alternators aren't good for motor conversions because they have too many poles for any off the shelf motor controller to handle. At least that's what I thought when I was trying to figure out if it was feasible. A more minor problem is that alternators also tend to have inefficient thick laminations.

Replacing the whole alternator with a permanent magnet motor would be my preference, but getting it to work with the serpentine belt and adding a second tensioner are kind of annoying.

It might be easier to make a custom rotor for the alternator with less pole pairs but you need to know your physics.

As far as voltage and stuff goes, it's pretty simple, just match the maximum torque on the alternator pulley. Rough estimate is 1kW at 1400rpm idle (2x crank speed) = 7 Nm for a smaller alternator, double for some newer cars. Set the motor controller's current limit to whatever produces that torque. A larger pulley will give you proportionally more up to the limit of the belt and tensioner.

alternators are just three phase motors that uses a rectifier to 14.vDC have you ever cracked one open?

[serialk11r]

Originally Posted by Tahoe_Hybrid

alternators are just three phase motors that uses a rectifier to 14.vDC have you ever cracked one open?

Yes they are "just" 3 phase motors with a variable rotor field.

Controlling them is still a problem compared to other motors for the reasons mentioned (also the rotor field is another variable to optimize) and they are less efficient.