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From: Sjouke Burry on 11 Mar 2010 19:11
Michael wrote:
> Why do vehicle alternators not employ permanent (Nd) magnets?

Because they use the dc magnetizing current to adjust
the output voltage.
From: John Larkin on 11 Mar 2010 23:37
On Thu, 11 Mar 2010 15:09:49 -0800 (PST), Michael
<mrdarrett(a)gmail.com> wrote:

>Why do vehicle alternators not employ permanent (Nd) magnets?

Some motorcycle alternators do, spinning a PM field and using fixed
output windings. The regulators generally short the output to keep the
charging current down. That seems to work for the fairly low power
needs of a motorcycle.

John

From: Michael on 12 Mar 2010 00:29
On Mar 11, 8:37 pm, John Larkin
<jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote:
> On Thu, 11 Mar 2010 15:09:49 -0800 (PST), Michael
>
> <mrdarr...(a)gmail.com> wrote:
> >Why do vehicle alternators not employ permanent (Nd) magnets?
>
> Some motorcycle alternators do, spinning a PM field and using fixed
> output windings. The regulators generally short the output to keep the
> charging current down. That seems to work for the fairly low power
> needs of a motorcycle.
>
> John


Wow, thanks! I'll have to look into those.

Thanks to all for the replies

Michael
From: default on 12 Mar 2010 09:25
On Thu, 11 Mar 2010 15:09:49 -0800 (PST), Michael
<mrdarrett(a)gmail.com> wrote:

>Why do vehicle alternators not employ permanent (Nd) magnets?

They do. Motorcycles have been PM'd for many years now. Modern ones
can compete with car alternators for power produced. You're familiar
with outboards? Tractors? Even the lowly Briggs added an extra coil
to their early electric start engines using the magneto magnet to
charge the battery.

For some reason cars are often the last vehicles to apply
technological improvements.

http://home.earthlink.net/~trinomial/chgtypes.html
--
From: TE Cheah on 12 Mar 2010 07:21
| car alternators are regulated by adjusting the current to their
| field coils; in effect their motor constants are changed by the
| regulator circuit. This makes them fairly easy to control with very
| little, and efficient, circuitry.

I loath the amperes wasted by alternator's excitor circuit before
engines are started successfully. Does a brushless alternator
likewise waste amperes before an engine is started successfully ?


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