Re: EV Generator

[jklein <jklein@hpower.com>]

FYI, modern alternators have more then 6 diodes. I have seen as many as 12. This
is done to try to clean up the power for the computers in the cars. I use to work
for an auto parts manufacturer, and I was a little surprised to see this myself.

Joseph F. Klein
Sr. Process Technologist
H-Power Corp.

LEE A HART wrote:

> > If a car alt. were 50 % eff. they would burn up when I ran them at
> > these power levels and they didn't. They run about 3khz to 35khz with
> > 7 poles. Check your sources.       electricly yours jerry dycus
>
> I have tested car alternators too, and they really are only 50-60% efficient
> at best. (It always amazes me that the auto companies can design such
> inefficient motors and generators :-)
> It's not hard to see why their efficiency is so low. Let's assume you spin an
> alternator with a 1 HP motor. 1 HP = 746 watts, so that's our power input.
>
> Let's be generous and say the v-belt is 95% efficient. Then we have 746w x
> 0.95 = 709 watts at the alternator's shaft.
>
> Let's continue to be generous and say the fan only uses 5%. Now we have 709w x
> 0.95 = 673 watts left to spin the rotor.
>
> A good quality 1 HP motor or generator is about 80% efficient. Its losses
> include bearing friction, brush (slip ring) drag, magnetization, winding
> resistance, and rotor wind resistance losses. So 673w x 0.8 = 538 watts of
> electrical energy.
>
> But there is also an internal 6-diode bridge rectifier. Each diode has a 1v
> drop, and there are two in series for each path for a 2v drop. So you have to
> generate 16v to get a 14v output. 14v/16v is 88%, so we have 538w x 0.88 = 471
> watts left (34 amps at 14v).
>
> The field winding and regulator draw about 1 amp, so they take 14v x 1a = 14
> watts. 471w - 14w = 457 watts output.
>
> So where do we stand? 457 watts out / 746 watts in = 60% efficiency.
>
> Lee Hart                     If you would not be forgotten
> 4209 France Ave. N.          Soon as you are dead and rotten
> Robbinsdale, MN 55422 USA    Either write things worth the reading
> phone (612) 533-3226         Or do things worthy of the writing
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