|
Home > Archive > Alternative Power sources > December 2005 > Car Alternators?
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
|
|
| James Storm 2005-12-18, 11:21 am |
| Car alternators use diodes to rectify a/c to d/c. Has anyone tested them
without there diodes? I am curious as to the voltage and frequency
output is when unregulated and what was the alternator speed? Is there
enough of anything there to use?
Thanks.
--
James Storm
aka Stormy Weather
jstorm@ptd.net
| |
| nospam@nouce.bellatlantic.net 2005-12-18, 11:21 am |
| On Sun, 18 Dec 2005 09:51:33 -0500, James Storm <jstorm@ptd.net>
wrote:
>Car alternators use diodes to rectify a/c to d/c. Has anyone tested them
>without there diodes? I am curious as to the voltage and frequency
>output is when unregulated and what was the alternator speed? Is there
>enough of anything there to use?
>Thanks.
Yes, years ago it was sometimes done by amatuers. The alternator was
left intact with diodes and regulator but the AC side windings were
brought out and used with three transformers (delta or Y) to step up
the 13Vac to around 600-800V for then common tube radios. Power
was around 400-800W regions and not taxing capability. Regualtion
was around 10% at 13.8 for the DC side and around would wander
between 630 to 780 for a nominal 700V system (fine for tube transmit).
Frequency is all over the map but 200 at idle and over 1000Hz at
nominal cruse speeds sticks in my mind. Anyone that has worked
with mobile radio of other gear knows alternator whine.
Heres the case, if run at constant RPM the frequency is fairly high
(above 60hz) but the voltage will depend on the field excitation but
can be anywhere from 12V to as high as 40(thereabouts).
Allison
| |
| Duane C. Johnson 2005-12-18, 2:21 pm |
| Hi James;
James Storm <jstorm@ptd.net> wrote:
> Car alternators use diodes to rectify a/c to d/c.
> Has anyone tested them without there diodes?
> I am curious as to the voltage and frequency output
> is when unregulated and what was the alternator speed?
The frequency is dependent on the speed the alternator
is turning and the voltage of the 3 phase AC is
somewhat dependent on the field excitation current.
Often up to 36VAC, sometimes as high as 72VAC.
Frequency can be quit high. Exceeding 1000 Hz at times.
Some micro hydro users have used alternators in this
fashion. They would use surplus 3 phase 400Hz
transformers to step the voltage up for transmission
to a location near the house. They then used another
transformer to step the high voltage back down.
Rectifier diodes can now be used in the conventional
way to charge the system battery.
> Is there enough of anything there to use?
> Thanks.
Duane
--
Home of the $35 Solar Tracker Receiver
http://www.redrok.com/led3xassm.htm [*]
Powered by \ \ \ //|
Thermonuclear Solar Energy from the Sun / |
Energy (the SUN) \ \ \ / / |
Red Rock Energy \ \ / / |
Duane C. Johnson Designer \ \ / \ / |
1825 Florence St Heliostat,Control,& Mounts |
White Bear Lake, Minnesota === \ / \ |
USA 55110-3364 === \ |
(651)426-4766 use Courier New Font \ |
redrok@redrok.com (my email: address) \ |
http://www.redrok.com (Web site) ===
| |
|
|
<nospam@nouce.bellatlantic.net> wrote in message
news:r1uaq1h62uc67s3bkd7ot9dm465hqeuln2@4ax.com...
> On Sun, 18 Dec 2005 09:51:33 -0500, James Storm <jstorm@ptd.net>
> wrote:
>
>
> Yes, years ago it was sometimes done by amatuers. The alternator was
> left intact with diodes and regulator but the AC side windings were
> brought out and used with three transformers (delta or Y) to step up
> the 13Vac to around 600-800V for then common tube radios. Power
> was around 400-800W regions and not taxing capability. Regualtion
> was around 10% at 13.8 for the DC side and around would wander
> between 630 to 780 for a nominal 700V system (fine for tube transmit).
> Frequency is all over the map but 200 at idle and over 1000Hz at
> nominal cruse speeds sticks in my mind. Anyone that has worked
> with mobile radio of other gear knows alternator whine.
>
> Heres the case, if run at constant RPM the frequency is fairly high
> (above 60hz) but the voltage will depend on the field excitation but
> can be anywhere from 12V to as high as 40(thereabouts).
>
>
> Allison
It would have to be a lot higher frequency than 1000 Hz. A car engine
fast-idles at 1000 RPM and often runs at over 2500 RPM at cruising speed.
An alternator generally runs much faster than the engine due to its driven
pulley being much smaller than the drive pulley on the engine. Assuming the
stator-rotor combination in an alternator is configured to reverse polarity
twice each revolution, at load-bearing speeds, the frequency could easily be
above 5000 Hz.
| |
| SolarFlare 2005-12-18, 5:21 pm |
| You forget one big thing. If the alternator is from an
American built design, they surely must have gotten the
alternator down to half or quarter of a pole by now to
cheapen the design as much as they could. Your freq
calcs would be off by a large factor then.
LOL
"JoeSP" <olegp@telus.net> wrote in message
news:Ocjpf.8573$ic1.1614@edtnps90...
> It would have to be a lot higher frequency than 1000
Hz. A car engine
> fast-idles at 1000 RPM and often runs at over 2500
RPM at cruising speed.
> An alternator generally runs much faster than the
engine due to its driven
> pulley being much smaller than the drive pulley on
the engine. Assuming the
> stator-rotor combination in an alternator is
configured to reverse polarity
> twice each revolution, at load-bearing speeds, the
frequency could easily be
> above 5000 Hz.
>
>
| |
| nospam@nouce.bellatlantic.net 2005-12-18, 6:21 pm |
| On Sun, 18 Dec 2005 19:59:42 GMT, "JoeSP" <olegp@telus.net> wrote:
>
><nospam@nouce.bellatlantic.net> wrote in message
>news:r1uaq1h62uc67s3bkd7ot9dm465hqeuln2@4ax.com...
>
>
>It would have to be a lot higher frequency than 1000 Hz. A car engine
>fast-idles at 1000 RPM and often runs at over 2500 RPM at cruising speed.
Now remember this RPM (the M is in minutes) and HZ (is cycles per
Second) to convert one from the factor is 60.
So 1200 RPM is 20 RPS and if an alternator has 12 poles that's only
240hz. Assuming a single phase alternator. Since most are three
phases we'll have to divide number of poles by number phases
getting only 4. Multiply 20RPS by 4 poles we get 80Hz.
If we take the alternator to 6000 RPM (cruzin at 80 in 3rd gear
in a R2 powered 82 toyota) we are at 1000RPS and that 12 pole
alternator is cranking a whopping 4000hz.
The usual ratio is around 2:1 from engine accessory drive to
alternator.
Most auto alternators are around 3-5 poles per phase especially
older ones.
So at the extreme your likely right. At the time the articles were
written the usual 289/263/350 V8 idled at 550-600 and cruse was
around 2000RPM with redline (road roaches) under 4500rpm.
So for some old 454 powered Caddy slogging down the road the
alternator might just be putting out at 2400 Alternator shaft RPM
with an 9 pole alternator (GM ya know) for a astounding 120hz.
And theres a chance i'm high by two on this if memory boffed it.
Allison
| |
| clare at snyder.on.ca 2005-12-18, 9:21 pm |
| On Sun, 18 Dec 2005 15:04:28 GMT, nospam@nouce.bellatlantic.net wrote:
>On Sun, 18 Dec 2005 09:51:33 -0500, James Storm <jstorm@ptd.net>
>wrote:
>
>
>Yes, years ago it was sometimes done by amatuers. The alternator was
>left intact with diodes and regulator but the AC side windings were
>brought out and used with three transformers (delta or Y) to step up
>the 13Vac to around 600-800V for then common tube radios. Power
>was around 400-800W regions and not taxing capability. Regualtion
>was around 10% at 13.8 for the DC side and around would wander
>between 630 to 780 for a nominal 700V system (fine for tube transmit).
>Frequency is all over the map but 200 at idle and over 1000Hz at
>nominal cruse speeds sticks in my mind. Anyone that has worked
>with mobile radio of other gear knows alternator whine.
>
>Heres the case, if run at constant RPM the frequency is fairly high
>(above 60hz) but the voltage will depend on the field excitation but
>can be anywhere from 12V to as high as 40(thereabouts).
>
>
>Allison
Can actually go well above 120 volts on the DC side unregulated.
| |
| meow2222@care2.com 2005-12-19, 1:21 am |
| James Storm wrote:
> Car alternators use diodes to rectify a/c to d/c. Has anyone tested them
> without there diodes? I am curious as to the voltage and frequency
> output is when unregulated and what was the alternator speed?
Car alts do 2-3 times engine speed, so they go over 10,000 rpm.
> Is there
> enough of anything there to use?
50A x 15v = 750 watts. Remove regulation and your V can triple, giving
2kW or so, if you ever manage to spin them fast enough.
Their other downside is that they are wound field, not permanent
maggot, so they consume some of what they produce. Also there is some
question over whether dc must be applied to the field to get them to
begin producing output. I once used to run one to charge dead
batteries, and it always fired up ok, but whether this residual
magnetism can be relied on for self starting I dont know.
NT
| |
| meow2222@care2.com 2005-12-19, 1:21 am |
| SolarFlare wrote:
> You forget one big thing. If the alternator is from an
> American built design, they surely must have gotten the
> alternator down to half or quarter of a pole by now to
> cheapen the design as much as they could. Your freq
> calcs would be off by a large factor then.
>
>
> LOL
Lol. Still trying to work out how to design that...
NT
| |
| daestrom 2005-12-19, 5:21 pm |
|
<nospam@nouce.bellatlantic.net> wrote in message
news:tnkbq1l4r7pp4urm56kchqklefck5vrp67@4ax.com...
> On Sun, 18 Dec 2005 19:59:42 GMT, "JoeSP" <olegp@telus.net> wrote:
>
>
> Now remember this RPM (the M is in minutes) and HZ (is cycles per
> Second) to convert one from the factor is 60.
>
> So 1200 RPM is 20 RPS and if an alternator has 12 poles that's only
> 240hz. Assuming a single phase alternator. Since most are three
> phases we'll have to divide number of poles by number phases
> getting only 4. Multiply 20RPS by 4 poles we get 80Hz.
>
Sorry, but your 'alternator math' is a bit faulty. If a unit has 12 poles
and you spin it at 1200 RPM, you get 120 hz, not 240. That is because it
takes two poles to create one cycle (both the 'N' and 'S' pole must pass a
given point to complete a cycle). That adds another factor of '2'. f =
n*p/120, where n is speed in RPM and p is the number of poles. (120 is
simply your '60' times '2').
Also, a three phase alternator does not need three times as many poles.
Although there are three times the armature windings, the number of poles is
the same. So a 12 pole, 1200 RPM 3-phase machine still generates 120 hz.
> If we take the alternator to 6000 RPM (cruzin at 80 in 3rd gear
> in a R2 powered 82 toyota) we are at 1000RPS and that 12 pole
> alternator is cranking a whopping 4000hz.
>
> The usual ratio is around 2:1 from engine accessory drive to
> alternator.
>
> Most auto alternators are around 3-5 poles per phase especially
> older ones.
Not in the US. Most US alternators are actually more on the order of 24 to
28 poles. Running the engine at cruising speed of 2000 RPM, with 2:1 belt
drive gives you about 933 hz (4000*28/120) and 3-phase output, that is then
rectified to DC.
At 500 RPM idle, frequency is about 233 hz.
daestrom
| |
| daestrom 2005-12-19, 5:21 pm |
|
"SolarFlare" <sfl.are@hot.mail.invalid> wrote in message
news:rtSdncL25tAAWTjeRVn-vQ@golden.net...
> You forget one big thing. If the alternator is from an
> American built design, they surely must have gotten the
> alternator down to half or quarter of a pole by now to
> cheapen the design as much as they could. Your freq
> calcs would be off by a large factor then.
>
Actually, US alternators have gone 'the other way'. One common design has
28 poles. But only one winding on the rotor. By literally coiling the
winding around the shaft (on a spacer spool), it creates a magnetic field
that is aligned along the shaft. But then a pair of flat disks with 14
'teeth' cut into them are placed on opposite ends of the shaft against each
side of the coil. The 'teeth' from each disk are 'folded' over bent so they
point towards the opposite disk, and one disk is rotated slightly so its
teeth fit between the bent teeth of the other disk. The result is 28
'teeth' overlapping the outer rim of the coil, and 28 alternating (no pun
intended) 'N' and 'S' poles around the rim.
daestrom
| |
| nospam@nouce.bellatlantic.net 2005-12-19, 6:21 pm |
| On Mon, 19 Dec 2005 20:26:53 GMT, "daestrom"
<daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:
>
>Sorry, but your 'alternator math' is a bit faulty. If a unit has 12 poles
>and you spin it at 1200 RPM, you get 120 hz, not 240. That is because it
>takes two poles to create one cycle (both the 'N' and 'S' pole must pass a
>given point to complete a cycle). That adds another factor of '2'. f =
>n*p/120, where n is speed in RPM and p is the number of poles. (120 is
>simply your '60' times '2').
Thanks for the refresh. I did say at the end I was likely off by two
but the brain been doing the stuff for decades and it's an error I
still often make and know it. ;)
My basis for the alternator was a late 60s GM model. I know htey have
both gotten simpler in construction and a bit better.
>Not in the US. Most US alternators are actually more on the order of 24 to
>28 poles. Running the engine at cruising speed of 2000 RPM, with 2:1 belt
>drive gives you about 933 hz (4000*28/120) and 3-phase output, that is then
>rectified to DC.
>
>At 500 RPM idle, frequency is about 233 hz.
>
>daestrom
Falls in like with my ear (alternator whine on some 2m radios!).
Allison
| |
| SolarFlare 2005-12-19, 9:21 pm |
| oooops. Looks like many have very fast clocks and need
to have "hand" training again...LOL
Hz = cycles per second not CPM cycles per minute
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in
message
news:hIEpf.52903$ME5.51344@twister.nyroc.rr.com...
> Sorry, but your 'alternator math' is a bit faulty.
If a unit has 12 poles
> and you spin it at 1200 RPM, you get 120 hz, not 240.
That is because it
> takes two poles to create one cycle (both the 'N' and
'S' pole must pass a
> given point to complete a cycle). That adds another
factor of '2'. f =
> n*p/120, where n is speed in RPM and p is the number
of poles. (120 is
> simply your '60' times '2').
>
> Also, a three phase alternator does not need three
times as many poles.
> Although there are three times the armature windings,
the number of poles is
> the same. So a 12 pole, 1200 RPM 3-phase machine
still generates 120 hz.
>
in 3rd gear[color=darkred]
that 12 pole[color=darkred]
drive to[color=darkred]
phase especially[color=darkred]
>
> Not in the US. Most US alternators are actually more
on the order of 24 to
> 28 poles. Running the engine at cruising speed of
2000 RPM, with 2:1 belt
> drive gives you about 933 hz (4000*28/120) and
3-phase output, that is then
> rectified to DC.
>
> At 500 RPM idle, frequency is about 233 hz.
>
> daestrom
>
>
| |
| daestrom 2005-12-20, 7:21 pm |
|
"SolarFlare" <sfl.are@hot.mail.invalid> wrote in message
news:FuqdnTCJLtlczjrenZ2dnUVZ_smdnZ2d@golden.net...
> oooops. Looks like many have very fast clocks and need
> to have "hand" training again...LOL
>
>
> Hz = cycles per second not CPM cycles per minute
>
What you on about now?
Nowhere did I calculate CPM, so you seem to have a reading comprehension
problem again.
daestrom
| |
| SolarFlare 2005-12-20, 8:21 pm |
| Not getting enough sleep again? Got an algorythm to
resolve that just won't resolve?...LOL
I was commenting *to* you...not **about** you.
Take a pill. over to you...
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in
message
news:vy%pf.53030$ME5.32769@twister.nyroc.rr.com...
>
> What you on about now?
>
> Nowhere did I calculate CPM, so you seem to have a
reading comprehension
> problem again.
>
> daestrom
>
>
|
|
|
|
|