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'[EE]: Car alternator as a bldc motor'
2012\06\07@160957 by Luis Moreira

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Hi Guys,
Just came across some videos on YouTube about using a car alternator as a
sort of bldc motor, as any of you tried this before? It seems like a very
neat thing to try...  Any results that you may want to share? I am curious
about speed and torque possible with one of these.
Best Regards
           Lui

2012\06\08@082453 by Moreira, Luis A

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Hi Guys,

I sent this email yesterday from my other email address but it didn't get to the list somehow... strange.
Anyway, just came across some videos on YouTube about using a car alternator as a sort of bldc motor, as any of you tried this before? It seems like a very neat thing to try...  Any results that you may want to share? I am curious about speed and torque possible with one of these.
Best Regards
           Luis

2012\06\08@090443 by Ruben Jönsson

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It did get to the list, I saw it earlier.

/Ruben

>
>
> Hi Guys,
>
> I sent this email yesterday from my other email address but it didn't get to
> the list somehow... strange.

===========================================
Ruben Jönsson
AB Liros Electronic
Box 9124
200 39 Malmö Sweden
http://www.liros.se
Tel +46 40142078
============================================

2012\06\08@090550 by M.L.

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On Fri, Jun 8, 2012 at 8:24 AM, Moreira, Luis A <spam_OUTLuis.MoreiraTakeThisOuTspamccfe.ac.uk> wrote:
>
>
> Hi Guys,
>
> I sent this email yesterday from my other email address but it didn't get to the list somehow... strange.
> Anyway, just came across some videos on YouTube about using a car alternator as a sort of bldc motor, as any of you tried this before? It seems like a very neat thing to try...  Any results that you may want to share? I am curious about speed and torque possible with one of these.
> Best Regards
>            Luis


Yes it can be done. They're very inefficient as a general rule but I
think you can get good speed out of them. Torque is probably not very
high.
They would know more about this at the evtech list:
http://evtech.org/

--
Martin K.

2012\06\08@105736 by John Ferrell

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I am a fan of Youtube. There are many really good videos there from repairing appliances to academic Lectures.
However, there seems to be an increasing tendency for pranksters to present convincing demonstrations of things that just are not so.

In the case of brushless motors I have just enough experience(model airplanes) and information (internet) to want to believe posts like this without adequate evidence. If you do any lab work to prove or disprove the use of an alternator in this manner you would do us all a favor in sharing it!

On 6/8/2012 8:24 AM, Moreira, Luis A wrote:
>
> Hi Guys,
>
> I sent this email yesterday from my other email address but it didn't get to the list somehow... strange.
> Anyway, just came across some videos on YouTube about using a car alternator as a sort of bldc motor, as any of you tried this before? It seems like a very neat thing to try...  Any results that you may want to share? I am curious about speed and torque possible with one of these.
> Best Regards
>              Luis
>

-- John Ferrell W8CCW
“During times of universal deceit,
  Telling the TRUTH becomes a revolutionary act”
     George Orwell


2012\06\08@111913 by RussellMc

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         BCC: Peter - comment welcomed.

> Anyway, just came across some videos on YouTube about using a car alternator as a sort of bldc motor, as any of you tried this before? It seems like a very neat thing to try...  Any results that you may want to share? I am curious about speed and torque possible with one of these.

Please provide some links to videos etc that you consider pertinent.

A car alternator has in the vast majority of a rotor  which is excited
via brush feed. That makes it non-brushless to start as is.

When the device is an alternator the 'field'  is a rotating magnet and
the power input is via shaft mechanical drive and the brushes need
transfer only field power so brush needs are far lighter than for
power feed via brushes. Rotor is usually fix magnetised in polarity so
DC feed via sliprings rather than a commutator can be used.

For the device to be a motor if the rotor is still a rotor (and not
clamped with stator as rotor as is done for some re-applications) then
rotor can still be a brush fed "DC" magnet. Stator coils now have
rotating field applied at full power and system should be able to be
made to work OK.  This is NOT brushless but it uses sliprings and not
commutator and electrical energy transfer to rotor is small % wise.
Effiiciency needs to account for DC magnet drive but should be able to
be "OK" [tm].

If the rotor is re-fitted to have permanent magnets (as is sometimes
done for alternator applications) a true BLDC can be produced.
Efficiency seems likely to be similar to other implementations.

I've copied this to a man who actually knows the real answer and it
will be interesting to see what he says :-).


             Russell

2012\06\08@112130 by M.L.

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On Fri, Jun 8, 2012 at 10:57 AM, John Ferrell <.....jferrell13KILLspamspam@spam@triad.rr.com> wrote:
> I am a fan of Youtube. There are many really good videos there from
> repairing appliances to academic Lectures.
> However, there seems to be an increasing tendency for pranksters to
> present convincing demonstrations of things that just are not so.
>
> In the case of brushless motors I have just enough experience(model
> airplanes) and information (internet) to want to believe posts like this
> without adequate evidence. If you do any lab work to prove or disprove
> the use of an alternator in this manner you would do us all a favor in
> sharing it!
>

John,
It's not magic! As you probably know, the difference between a motor
and an alternator like this is a "simple" issue of commutation. You
certainly need some electronics to control the phases. Otherwise it
should work.

-- Martin K

2012\06\08@122954 by Isaac Marino Bavaresco
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Em 8/6/2012 12:18, RussellMc escreveu:

{Quote hidden}

If the rotor is short-circuited, then we have a 3-phase induction motor...


Isaac

2012\06\08@124351 by RussellMc

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> If the rotor is short-circuited, then we have a 3-phase induction motor....

I haven't examined an auto alternator with that in mind BUT a squirrel
cage motors is a very very specialised beast indeed, optimised to
achieve the rather interesting dual task of exciting the rotor and
applying a rotating motive field to drive it. The rotor excitation is
achieved by the slip frequency field whereas a brushed DC slipring fed
field is  mechanically vastly vastly* different. May be able to be
made to rotate but I'd doubt it would be able to be made to make much
power at all**.


      Russell

* [TM]

** But, as ever, I may be wrong.  Just ask Bob B :-)

2012\06\08@142344 by John Ferrell

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With Brushless Motors, the devil is in the details!

Start up, timing, switching, loading, transients, noise (both electrical & audible) are all problems to address. Handling a hundred or so amps is OK, but a brush less the size of an alternator would likely be in the 4Kw-5hp range with Currents & voltages that are outside my normal bounds. I would guess that the form factor would dictate an In Runner which is inclined to be high revving, short power band...
OTH, the more I learn. the more I find that I don't know... I wonder what electric vehicles are currently using... off to Google...

On 6/8/2012 11:20 AM, M.L. wrote:
{Quote hidden}

-- John Ferrell W8CCW
“During times of universal deceit,
  Telling the TRUTH becomes a revolutionary act”
     George Orwell


2012\06\08@142813 by Isaac Marino Bavaresco

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Em 8/6/2012 13:43, RussellMc escreveu:
>> If the rotor is short-circuited, then we have a 3-phase induction motor....
> I haven't examined an auto alternator with that in mind BUT a squirrel
> cage motors is a very very specialised beast indeed, optimised to
> achieve the rather interesting dual task of exciting the rotor and
> applying a rotating motive field to drive it. The rotor excitation is
> achieved by the slip frequency field whereas a brushed DC slipring fed
> field is  mechanically vastly vastly* different. May be able to be
> made to rotate but I'd doubt it would be able to be made to make much
> power at all**.
>
>
>        Russell
>
> * [TM]
>
> ** But, as ever, I may be wrong.  Just ask Bob B :-).


And if the rotor is short-circuited through a rheostat (well, not
exactly a short circuit) then we get a "torque motor" (a motor that
maintains a nearly constant torque, even stalled).


Isaac

2012\06\08@160455 by Matt Bennett

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On Fri, June 8, 2012 1:23 pm, John Ferrell wrote:
> With Brushless Motors, the devil is in the details!
>
> Start up, timing, switching, loading, transients, noise (both electrical
> & audible) are all problems to address. Handling a hundred or so amps is
> OK, but a brush less the size of an alternator would likely be in the
> 4Kw-5hp range with Currents & voltages that are outside my normal
> bounds. I would guess that the form factor would dictate an In Runner
> which is inclined to be high revving, short power band...
> OTH, the more I learn. the more I find that I don't know... I wonder
> what electric vehicles are currently using... off to Google...

>From my discussions with some local EV builders, AC induction motors
(ACIM) are the most popular. Brushless motors use permanent magnets, and
at least the last time I surveyed the landscape, in the range of power an
EV needs, a brushless motor is just too heavy.

I'd love to see a car with each wheel powered individually with its own
hub-motor, but at least for now, the unsprung weight makes the vehicle
impractical (poor handling and the very real possibility of a pot-hole not
just bending a rim, but taking out a very expensive piece of your
drivetrain).

I would love to be shown just exactly how wrong I am.

Regards,

Matt Bennett
Just outside of Austin, TX
30.51,-97.91

The views I express are my own, not that of my employer, a large
multinational corporation that you are familiar with

2012\06\08@192233 by M.L.

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On Fri, Jun 8, 2012 at 4:04 PM, Matt Bennett <.....mattpiclistKILLspamspam.....hazmat.com> wrote:
> From my discussions with some local EV builders, AC induction motors
> (ACIM) are the most popular. Brushless motors use permanent magnets, and
> at least the last time I surveyed the landscape, in the range of power an
> EV needs, a brushless motor is just too heavy.

Most builders use series wound DC motors. The "Advanced DC" 9" motor
is the most common.
http://evalbum.com/mtrbr

AC Propoulsion and Siemens are likely the most popular for AC conversions.

-- Martin K

2012\06\09@000111 by RussellMc

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> I've copied this to a man who actually knows the real answer and it
> will be interesting to see what he says :-).

He said:

Hi Rusl,yep did this for Bosch Australia in 88,10 N-m on their 85 amp
alternator,ok for engines up to 1000 cc,had sychronous retification
built in.
But too expensive back then due to cost of electronics!

_______________

24 years ago.
Nothing new under the sun.

10 N.m = 1 kg.m = 1 Watt per RPM.
ie 1000 Watts at 1000 rpm and 10 kW at 10,000 RPM if it would work at
those revs (DTTAH).

I assume the comment about 1000cc motors related to use as a starter
motor. Maybe not.


       Russel

2012\06\09@073115 by John Gardner

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....Nothing new under the sun.

Indeed. 1901...

http://en.wikipedia.org/wiki/Lohner-Porsche



On 6/8/12, RussellMc <EraseMEapptechnzspam_OUTspamTakeThisOuTgmail.com> wrote:
{Quote hidden}

>

2012\06\09@074410 by John Gardner

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No reference handy, but Porsche later designed a hub-motor
electric (1920s?) which featured regenerative braking - Other
aspects of that vehicle later showed up in the Volkswagen.

Jac

2012\06\11@145308 by Electron

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Mechanical power may be transmitted from engines placed just above the wheels
and suspensions, i.e. the engines would be acting as sprung masses.

I've even seen hydraulic power transmission (think about Christini 2-wheel drive
bikes).

Cheers,
Mario



At 22.04 2012.06.08, you wrote:
{Quote hidden}

>

2012\06\12@100317 by Matt Bennett

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On Mon, June 11, 2012 1:52 pm, Electron wrote:
>
>
> Mechanical power may be transmitted from engines placed just above the
> wheels
> and suspensions, i.e. the engines would be acting as sprung masses.

No doubt- my curiosity with hub-motors is driven by a few things- probably
mostly about how it would change the paradigm of automotive design- move
the motive force of the vehicle- open up the center of the vehicle.  Once
you have to include transmissions and such, you have a couple very large
area between the wheels that must be dedicated to the drivetrain.

> I've even seen hydraulic power transmission (think about Christini 2-wheel
> drive
> bikes).

As I understand hydraulic power transmission, it is quite inefficient- the
wikipedia article quotes at least 25% transmission losses- Which may be
competitive with current technology, but, particularly with an EV, this
type of loss translates into additional weight in batteries you must lug
around. And heat- lots of heat.

I have been expecting to see rock-crawler type vehicles with hydraulic
drive- but those in general are quite low speed (or only bursts of higher
speed), and weight is not as critical an issue.


Matt Bennett
Just outside of Austin, TX
30.51,-97.91

The views I express are my own, not that of my employer, a large
multinational corporation that you are familiar with

2012\06\12@115717 by John Gardner

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The figure usually bandied around for efficient "lock-up"
torque converters is 10% - Still not trivial...

Jac

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