M
Michael
Guest
Why do vehicle alternators not employ permanent (Nd) magnets?
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T
Tim Wescott
Guest
Michael wrote:
with its supporting circuitry it may be bigger than current technology.
An alternator that uses DC magnets will have an output voltage that is
very strongly coupled to it's speed and that cannot be adjusted.
Instead, you'd need to have some sort of a switching power supply
circuit to take whatever happened to come off the alternator and feed it
to the battery.
Normal 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.
--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
No, but by the time you finish surrounding a permanent field alternatorOn Mar 11, 4:05 pm, Jamie
jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
Michael wrote:
Why do vehicle alternators not employ permanent (Nd) magnets?
cost, heat, and size ?
Ah, so electromagnets have a larger magnetic field per unit volume?
with its supporting circuitry it may be bigger than current technology.
An alternator that uses DC magnets will have an output voltage that is
very strongly coupled to it's speed and that cannot be adjusted.
Instead, you'd need to have some sort of a switching power supply
circuit to take whatever happened to come off the alternator and feed it
to the battery.
Normal 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.
--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
J
Jamie
Guest
Michael wrote:
Why do vehicle alternators not employ permanent (Nd) magnets?
cost, heat, and size ?
S
Sjouke Burry
Guest
Michael wrote:
the output voltage.
Because they use the dc magnetizing current to adjustWhy do vehicle alternators not employ permanent (Nd) magnets?
the output voltage.
M
Michael
Guest
On Mar 11, 4:05 pm, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
Ah, so electromagnets have a larger magnetic field per unit volume?
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
Michael wrote:
Why do vehicle alternators not employ permanent (Nd) magnets?
cost, heat, and size ?
Ah, so electromagnets have a larger magnetic field per unit volume?
S
sparky
Guest
On Mar 11, 6:48 pm, Michael <mrdarr...@gmail.com> wrote:
The output voltage can be regulated much easier.On Mar 11, 4:05 pm, Jamie
jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
Michael wrote:
Why do vehicle alternators not employ permanent (Nd) magnets?
cost, heat, and size ?
Ah, so electromagnets have a larger magnetic field per unit volume?
J
John Larkin
Guest
On Thu, 11 Mar 2010 15:09:49 -0800 (PST), Michael
<mrdarrett@gmail.com> wrote:
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
<mrdarrett@gmail.com> wrote:
Some motorcycle alternators do, spinning a PM field and using fixedWhy do vehicle alternators not employ permanent (Nd) magnets?
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
M
Michael
Guest
On Mar 11, 8:37 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
Wow, thanks! I'll have to look into those.
Thanks to all for the replies
Michael
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 11 Mar 2010 15:09:49 -0800 (PST), Michael
mrdarr...@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
D
default
Guest
On Thu, 11 Mar 2010 15:09:49 -0800 (PST), Michael
<mrdarrett@gmail.com> wrote:
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
--
<mrdarrett@gmail.com> wrote:
They do. Motorcycles have been PM'd for many years now. Modern onesWhy do vehicle alternators not employ permanent (Nd) magnets?
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
--
T
TE Cheah
Guest
| 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 ?
| 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 ?
S
Sjouke Burry
Guest
TE Cheah wrote:
you are trolling.| 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 ?
You must hate 99.8 percent of all cars, or more likely
J
Jasen Betts
Guest
On 2010-03-12, TE Cheah <4ws@gmail.com> wrote:
'altenator warning' lamp.
I assume you mean a permanent magnet altenator, the are brushless
electromagnet field altenators.
--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
have you measured it? typically it is exactly enough to light the| 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.
'altenator warning' lamp.
no, but it could make the engine harder to start.Does a brushless alternator
likewise waste amperes before an engine is started successfully ?
I assume you mean a permanent magnet altenator, the are brushless
electromagnet field altenators.
--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
T
TE Cheah
Guest
| > I loath the amperes wasted by alternator's excitor circuit before
| > engines are started successfully.
| have you measured it?
No.
| typically it is exactly enough to light the 'altenator warning' lamp.
Wikipedia says a 70 amp alternator uses 2 amp as exciter, so I
think exciter should be activated only after engine starts.
| > Does a brushless alternator
| > likewise waste amperes before an engine is started successfully ?
| no, but it could make the engine harder to start.
How ?
| I assume you mean a permanent magnet altenator
No, see http://en.wikipedia.org/wiki/Alternator#Brushless_alternators
, in 4-09 1 Toyota salesman said new Camry ( but not lower models
) has this.
I suspect rare earth magnets can't be used ; heat will ruin these
magnets.
| > engines are started successfully.
| have you measured it?
No.
| typically it is exactly enough to light the 'altenator warning' lamp.
Wikipedia says a 70 amp alternator uses 2 amp as exciter, so I
think exciter should be activated only after engine starts.
| > Does a brushless alternator
| > likewise waste amperes before an engine is started successfully ?
| no, but it could make the engine harder to start.
How ?
| I assume you mean a permanent magnet altenator
No, see http://en.wikipedia.org/wiki/Alternator#Brushless_alternators
, in 4-09 1 Toyota salesman said new Camry ( but not lower models
) has this.
I suspect rare earth magnets can't be used ; heat will ruin these
magnets.
J
Jasen Betts
Guest
On 2010-03-13, TE Cheah <4ws@gmail.com> wrote:
current from separate (positive side) rectifier diodes (D+ terminal) which
was fed back into the altenator exitation (DF terminal) by the regulator
with it's stopped or at low RPM the exciter current coming from the lamp
circuit is is only a few hundered millianps, once the speed gets up
the rectifier kicks in to supply the power.
if that current is't taken mostly from the rectifiers then it's going
to cost the same,
if you're worried you could rig a horn relay (form C automotiver relay) to
cut the feed to the altenator when you activate the starter.
--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
the last altenator I looked closely at an altenator it took the exciter| > I loath the amperes wasted by alternator's excitor circuit before
| > engines are started successfully.
| have you measured it?
No.
| typically it is exactly enough to light the 'altenator warning' lamp.
Wikipedia says a 70 amp alternator uses 2 amp as exciter, so I
think exciter should be activated only after engine starts.
| > Does a brushless alternator
| > likewise waste amperes before an engine is started successfully ?
| no, but it could make the engine harder to start.
How ?
current from separate (positive side) rectifier diodes (D+ terminal) which
was fed back into the altenator exitation (DF terminal) by the regulator
with it's stopped or at low RPM the exciter current coming from the lamp
circuit is is only a few hundered millianps, once the speed gets up
the rectifier kicks in to supply the power.
Those things still need power for the exiters stationary winding.| I assume you mean a permanent magnet altenator
No, see http://en.wikipedia.org/wiki/Alternator#Brushless_alternators
if that current is't taken mostly from the rectifiers then it's going
to cost the same,
if you're worried you could rig a horn relay (form C automotiver relay) to
cut the feed to the altenator when you activate the starter.
--- news://freenews.netfront.net/ - complaints: news@netfront.net ---