[ausev] dc motors vs dc generators

[Clendon Gibson]

I am electrical engineer, but not a power specialist, so take what I say with a grain of salt.

The basic principle involved means that a DC generator and a motor can be the same. I would think in practice that there would be differences to watch for. For example, I would expect a DC generator to have voltage regulation circuitry that would be unnecessary to the motor. Applying power to the output of voltage regulation electronics would most likely not power the generator to act as a motor, and would likely damage the voltage regulation circuitry.

Why don't you post the generators and motors you have in mind. People with specific experience in them can tell you more about what you need to know.

Fundamentally the difference between the two is what is causing the motor/generator to turn. DC Motors turn because an electro-magnetic field is being applied to it. DC generators turn because something else, maybe wind power, a gas engine, etc... is driving it. If you discount where the energy is coming from and any add-on circuitry, generators and motors are pretty much the same.

Another thing that may be different, although it probably depends on the size of the motor/generator. I would think motors would tend to use permanent magnets. Some generators, notably car alternators, use an active coil that is charged by the cars battery to apply the magnetic field that the magnets would provide. The reason is that this allows a fairly simple voltage regulation. (If you change the voltage used in the active coil, the resulting voltage out changes proportionally. Can't do that with permanent magnets.)

If you want the basics of DC motors wikipedia is a great place to start.

http://en.wikipedia.org/wiki/Dc_motor#Brushless_DC_motors

----- Original Message ----
From: Donovan Becker <dbecker215 at hotmail.com>
To: ausev at austinev.org
Sent: Monday, April 23, 2007 3:08:48 PM
Subject: [ausev] dc motors vs dc generators

I know that there are a bunch of electrical engineers within this group, so 
I wanted ask if any of ya'll could tell me the difference between dc motors 
and dc generators. I read recently that they're the same, you just spin the 
shaft faster than the rated output to create energy. Is this true? In case 
your wondering this does involve ev's, just in an indirect manner. Thanks.

Donovan

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