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Posted by JimChufff on September 2, 2008, 12:35 pm
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Hi all,
Does anyone know anything about making an alternator work as a
motor? I've got a small diesel generator with an alternator attached,
which is currently started by hand. It would be nice to have it start
electrically (using the alternator, then switching to alternator mode
once its going). I have read some stuff about alternators being
structurally simlar to 3 phase motors, so I assume I need to do some
electrinics to make this work, but can't find anything specific on the
web.
thanks in advance
Jim Potter
UK
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Posted by Winston on September 2, 2008, 1:36 pm
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JimChufff wrote:
> Hi all,
> Does anyone know anything about making an alternator work as a
> motor?
...
I did that.
The torque was just dismal.
Your best bet is to buy the 'electric start' kit for your diesel.
--Winston
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Posted by Bruce in alaska on September 2, 2008, 7:56 pm
Please log in for more thread options wrote:
> JimChufff wrote:
>
> > Hi all,
> > Does anyone know anything about making an alternator work as a
> > motor?
> ...
>
> I did that.
>
> The torque was just dismal.
> Your best bet is to buy the 'electric start' kit for your diesel.
>
> --Winston
The way the "Big Boys" do that is to design the Genend with a Fixed
AC Stator, DC Shunt Field, DC Series Field, and DC Commutator. You
drive the DC Series Field, and Shunt Field, as a Motor, with DC,
and then once the engine is going, use the Series Field as the AC
Field winding, and also provide the DC for Starter Battery Charging.
All the Onan and Kohlers used this system for their small Genend
Started Generators.
--
Bruce in alaska
add <path> after <fast> to reply
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Posted by Neon John on September 2, 2008, 3:48 pm
Please log in for more thread options wrote:
>Hi all,
> Does anyone know anything about making an alternator work as a
>motor? I've got a small diesel generator with an alternator attached,
>which is currently started by hand. It would be nice to have it start
>electrically (using the alternator, then switching to alternator mode
>once its going). I have read some stuff about alternators being
>structurally simlar to 3 phase motors, so I assume I need to do some
>electrinics to make this work, but can't find anything specific on the
>web.
I've done that. That alternator behaves as a BLDC or synchronous motor,
depending on how you decide to drive it. IT makes a very inefficient motor
because it is designed to current limit by magnetic saturation when in normal
operation.
I cranked a low compression gasoline engine that had a compression release. I
had a 2:1 gear ratio between the alternator and engine (belt drive). With 24
volts available, the alternator could slowly spin up the engine with the
compression release activated. When I dropped the compression release lever,
the engine either started or coasted to a stop. The alternator lacked the
torque to turn it over against compression. I think that the chances of
starting a diesel are near zero.
What might work is the combination generator/starter motor as used on Cub
Cadet lawn tractors and some other brands. This is essentially the old
fashioned car generator, would and equipped with the proper switching to
operate as a starter motor.
I owned a old Lincoln gas-powered welder that used that method. Again, the
generator was geared to the engine by a 2:1 pulley system. It would turn the
engine over rather smartly. IT might do a small diesel, especially if you had
24 volts available.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
I like you ... you remind me of me when I was young and stupid.
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Posted by bw on September 2, 2008, 9:22 pm
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> Hi all,
> Does anyone know anything about making an alternator work as a
> motor? I've got a small diesel generator with an alternator attached,
> which is currently started by hand. It would be nice to have it start
> electrically (using the alternator, then switching to alternator mode
> once its going). I have read some stuff about alternators being
> structurally simlar to 3 phase motors, so I assume I need to do some
> electrinics to make this work, but can't find anything specific on the
> web.
>
> thanks in advance
>
> Jim Potter
> UK
No, you don't want to use an alternator.
Look up "starter/generator" common before the rise of alternators in the
1960s
Delco made them, same frame, just heavier windings on the armature.
You "could" use a Delco generator, but the windings will melt unless you
limit the start time severly.
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