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Home > Archive > Electrical Engineering > January 2007 > how to limit a DC generator ?
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how to limit a DC generator ?
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| I've got a plan to exchange the AC windings in a small 600w petrol
generator for a 12 v DC dynamo, as used to be used in cars, before
alternators , so i will have a battery charger for my boat.
However i want to have a way to control the maximum amp out put of the
generator, so that i can tune it to the engine power, i expect the full
output will be too much load for the engine.The engine is a fixed speed
@ 3000 rpm.
Any sugestions ?
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| John Gilmer 2007-01-08, 9:25 am |
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"Motor" <tadworth178@hotmail.com> wrote in message
news:1168263547.253050.290090@11g2000cwr.googlegroups.com...
> I've got a plan to exchange the AC windings in a small 600w petrol
> generator for a 12 v DC dynamo, as used to be used in cars, before
> alternators , so i will have a battery charger for my boat.
"They" stopped using "generators" on cars and switched over the
"alternators" for a good reason.
However, you still might be able to find a "voltage" regulator at any place
that handles automobile parts.
When the voltage regular fails on a dynamo system, the generator overheats.
The "hot part" in a dynamo is inside and can't be cooled. A dynamo
regulator usually has a current sensing coil. An alternator regular just
has the voltage control. In either case they control the output by
controlling the current if the "field" winding. The relay (in a relay
system) often "vibrates" on and off. It works.
If your problem is that the dynamo draws more shaft power than your engine
can comfortable supply, the solution is to change the pulley size and slow
down the dynamo.
>
> However i want to have a way to control the maximum amp out put of the
> generator, so that i can tune it to the engine power, i expect the full
> output will be too much load for the engine.The engine is a fixed speed
> @ 3000 rpm.
>
> Any sugestions ?
>
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| TimPerry 2007-01-08, 9:25 pm |
| Motor wrote:
> I've got a plan to exchange the AC windings in a small 600w petrol
> generator for a 12 v DC dynamo, as used to be used in cars, before
> alternators , so i will have a battery charger for my boat.
>
> However i want to have a way to control the maximum amp out put of the
> generator, so that i can tune it to the engine power, i expect the
> full output will be too much load for the engine.The engine is a
> fixed speed @ 3000 rpm.
>
> Any sugestions ?
assuming the existing generator is functioning and outputs sufficient power,
is an appropriate voltage and frequency... why not just get a battery
charger and run it? let say you decide on a peak load of 300W divide by
13.8 volts to get 21 amps.
they would let you run a couple of typical 10A chargers and you would get
the benefit of whatever regulation and 'smart' features that are built in to
the charger.
| |
| Dean Hoffman 2007-01-08, 9:25 pm |
| In article <1168263547.253050.290090@11g2000cwr.googlegroups.com>,
"Motor" <tadworth178@hotmail.com> wrote:
> I've got a plan to exchange the AC windings in a small 600w petrol
> generator for a 12 v DC dynamo, as used to be used in cars, before
> alternators , so i will have a battery charger for my boat.
>
> However i want to have a way to control the maximum amp out put of the
> generator, so that i can tune it to the engine power, i expect the full
> output will be too much load for the engine.The engine is a fixed speed
> @ 3000 rpm.
>
> Any sugestions ?
Farmers sometimes would use a rheostat and just turn a knob to
adjust the voltage. They used these on irrigation power units with
alternators. These engines would run hundreds of hours in the summer
and would ruin batteries due to overcharging. Some alternators must've
had defective voltage regulators.
Dean
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| John G 2007-01-09, 3:25 am |
|
"Motor" <tadworth178@hotmail.com> wrote in message
news:1168263547.253050.290090@11g2000cwr.googlegroups.com...
> I've got a plan to exchange the AC windings in a small 600w petrol
> generator for a 12 v DC dynamo, as used to be used in cars, before
> alternators , so i will have a battery charger for my boat.
>
> However i want to have a way to control the maximum amp out put of the
> generator, so that i can tune it to the engine power, i expect the
> full
> output will be too much load for the engine.The engine is a fixed
> speed
> @ 3000 rpm.
>
> Any sugestions ?
>
You may well find that changing the windings for DC 12volts and changing
the slipring commutator for
a segmented arrangement for DC will be too much. or even if you use an
AC arrangement and diodes the rewinding will be quite a task.
Much easier as someone else suggested, just get an inverter and a mains
battery charger.
A lot of small petrol generators already come with a DC output (not
yours I guess).
--
John G.
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| Setanta 2007-01-12, 3:25 am |
|
"Motor" <tadworth178@hotmail.com> wrote in message
news:1168263547.253050.290090@11g2000cwr.googlegroups.com...
> I've got a plan to exchange the AC windings in a small 600w petrol
> generator for a 12 v DC dynamo, as used to be used in cars, before
> alternators , so i will have a battery charger for my boat.
>
> However i want to have a way to control the maximum amp out put of the
> generator, so that i can tune it to the engine power, i expect the full
> output will be too much load for the engine.The engine is a fixed speed
> @ 3000 rpm.
>
> Any sugestions ?
>
Depends upon the dynamo
Lucas type C40 is very common (but you can check the body - its stamped
there)
The closed bracket type was normally used for agri/marine and had a
regulator called an RB108
The type of regulator for 12v car systems for this type of dynamo (with open
bracket - ventilation) is called an RB340
(All Lucas part numbers- although there were many spurious manufacturers)
3000 rpm should be fine for this dynamo - if there is no loading apart from
charging your batteries - although it might be an idea to assess exactly
what the loading will be.....how deep are the batteries cycled -
The closed type is regulated at a lower setpoint to prevent oveheating
If this isnt the case I'm sure I can find a solution given the dynamo type
There are a few different configuarions
Setanta
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| Thanks for your input, but this will be direct drive, no pulleys.
John Gilmer wrote:[color=darkred]
> "Motor" <tadworth178@hotmail.com> wrote in message
> news:1168263547.253050.290090@11g2000cwr.googlegroups.com...
>
> "They" stopped using "generators" on cars and switched over the
> "alternators" for a good reason.
>
> However, you still might be able to find a "voltage" regulator at any place
> that handles automobile parts.
>
> When the voltage regular fails on a dynamo system, the generator overheats.
> The "hot part" in a dynamo is inside and can't be cooled. A dynamo
> regulator usually has a current sensing coil. An alternator regular just
> has the voltage control. In either case they control the output by
> controlling the current if the "field" winding. The relay (in a relay
> system) often "vibrates" on and off. It works.
>
> If your problem is that the dynamo draws more shaft power than your engine
> can comfortable supply, the solution is to change the pulley size and slow
> down the dynamo.
>
| |
|
| Thanks for your input, but this will be direct drive, no pulleys.
John Gilmer wrote:[color=darkred]
> "Motor" <tadworth178@hotmail.com> wrote in message
> news:1168263547.253050.290090@11g2000cwr.googlegroups.com...
>
> "They" stopped using "generators" on cars and switched over the
> "alternators" for a good reason.
>
> However, you still might be able to find a "voltage" regulator at any place
> that handles automobile parts.
>
> When the voltage regular fails on a dynamo system, the generator overheats.
> The "hot part" in a dynamo is inside and can't be cooled. A dynamo
> regulator usually has a current sensing coil. An alternator regular just
> has the voltage control. In either case they control the output by
> controlling the current if the "field" winding. The relay (in a relay
> system) often "vibrates" on and off. It works.
>
> If your problem is that the dynamo draws more shaft power than your engine
> can comfortable supply, the solution is to change the pulley size and slow
> down the dynamo.
>
| |
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| tried this system with a 20 amp charger and the actual output is only a
couple of amps, i think there are big losses along the way with this
TimPerry wrote:
> Motor wrote:
>
> assuming the existing generator is functioning and outputs sufficient power,
> is an appropriate voltage and frequency... why not just get a battery
> charger and run it? let say you decide on a peak load of 300W divide by
> 13.8 volts to get 21 amps.
> they would let you run a couple of typical 10A chargers and you would get
> the benefit of whatever regulation and 'smart' features that are built in to
> the charger.
| |
| TimPerry 2007-01-20, 9:25 am |
| Motor wrote:[color=darkred]
> tried this system with a 20 amp charger and the actual output is only
> a couple of amps, i think there are big losses along the way with this
> TimPerry wrote:
battery chargers have built in resistance to prevent explosions when the
cables or battery become shorted,
there are not any other significant losses in a charger.
the current will depend on the battery parameters and state of charge.
any charging method that does not incorporate current limiting will be quite
dangerous.
| |
| Salmon Egg 2007-01-20, 5:25 pm |
| On 1/20/07 7:07 AM, in article
9aGdnVMjW6v4rS_YnZ2dnUVZ_rSjnZ2d@adelphia.com, "TimPerry"
<timperry@noaspamadelphia.net> wrote:
> battery chargers have built in resistance to prevent explosions when the
> cables or battery become shorted,
Most of these charges will have high leakage step down transformers rather
than resistive loading. The inductance is before the rectifiers.
Bill
-- Fermez le Bush--about two years to go.
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