Maximum Field Current for Delco 10SI Alternator?

[Ulysses]

Thanks to many people here I finally understand how to get a 12 volt
alternator to produce over 60 volts! I made a crude field control resistor
from some NiChrome wire and, powered by a 4 HP engine it is doing a fine job
of charging my 48 volt battery bank. I am, however, reluctant to connect
the output of the alternator directly to the field rotor without some
resistance inbetween. Will it damage the field coils if I give it full
power? It stll has the internal, original diodes in there so I'm not going
to try it quite yet in any case. The doides are holding up fine at about 30
amps @ 51 VDC but I suspect they are at their limit. That's about the limit
of 4 HP anyway.

 

[Martin Riddle]

I going to guess its around 4amps.
Is the 10si a 60 or 100amp animal?

Cheers

 

[clare at snyder dot ontario dot canada]

BEL electronics used to make an adapter box that ran 12 volts to the
feild and controlled voltage with the throttle (manually) MOST
alternator diodes are 250PIV or better

 

[Vaughn Simon]

I'm interested to hear what is in Don Young's adapter box. I've used power
from one
of these gadgets before but I've never had one open.

We bought one of those boxes 25 years ago for one of our service trucks. The
best answer to your question is "nothing but a big switch" The switch
disconnected the alternator from the truck's DC buss and simultaneously bypassed
the regulator. I don't know if we actually got 120 volts out, but it was
enough to run an electric drill in occasional service. Back then, most of our
trucks either had fanbelt-driven AC generators or 12 VDC/120 VAC MG sets.

Vaughn

 

[[email protected]]

... Many years ago Westinghouse researchers developed a heuristic for
bulb life vs voltage. Life varies as the thirteenth power of voltage
deviation from the nominal.

So a 120V 1000 hour bulb run at 240V would last 1000/(2^13) = 0.12 hours?

... I run ordinary 120 volt, 500 watt quartz-halogen lamps on 240 volts.
The output is dazzling

For how long?

Nick

 

[clare at snyder dot ontario dot canada]

Many lamps will go 3X nominal voltage before instaflashing. Many of those will
operate for satisfactory time periods at the instaflash voltage if brought up slowly,
as with a PWM controller.

If I remember properly from years back, Tungsten Halogen (or metal
halide) bulbs behave differently than standard incandescents due to
the "halide cycle". Tun at too low a voltage the tungsten boils off
and does not form a proper metal halide and does not redeposit on the
filament, causing severely shortened lamp life at moderate
undervoltage. Moderate overvoltage has much less effect , from what I
remember. Big problem with overvoltage on halides is from reduced
filament durability - so vibration and shock kill halide bulbs faster
when moderately overvoltage. This is why low voltage halogens stand up
better - as they have a heavier (higher current meand thicker
fillament) tungsten fillament than high votage bulbs, so they are
physically more robust.

Again, it's been 35+ years since I worked with the AV stuff on a daily
basis, and the halide bulbs were pretty new tech back then - and I've
forgotten a lot

 

[[email protected]]

Maybe, if the voltage is brought up slowly...

Probably 20 to 30 hours on mine.

Interesting. Don Klipstein says:

...bulb life is typically inversely proportional to applied voltage
raised to the 12th power. I often see 13.

So if a 120 V bulb lasts 750 hours at 120V, Don might expect it to last
(120/240)^12x750 = 0.18 hours (11 minutes) at 240V.

Nick

 

[[email protected]]

Only to folks like you who know just enough about a subject to argue.

Noticing apparent contradictions is one way to learn.

I'm curious whether you'd find it equally interesting to note that a 4 hour
photoflood lamp and a quartz heat lamp designed to operate at maybe 2000 deg K
behave quite differently in response to over-voltage?

Less so, since those are less common in houses.

Can I please, mas'a Nick, champion of all nitpickers, be permitted to round
13.1 to 13 for the purposes of idle conversation?

Of course. My friend Drew Gillett often rounds 60 to 100

BTW, any particular reason you chose 750 hours this time and 1000 hours
on the last round?

Just recalling an earlier posting...

Article 128163 of alt.energy.homepower:
From: [email protected]
Subject: Re: convert heater 110 to230??
Date: 17 Jul 2007 18:36:55 -0400
Organization: Villanova University

... I'm standing here looking at a 100 watt lightbulb running through a 1N4005
that I had handy, connected to a 240 volt heater outlet through a Jesus Cord.
Just as the *proper* math predicts, the bulb is burning at half brightness -
1/4 the power it would receive on 240.

Curious. If 240 is the rms value of a 240 volt waveform, ie the square root
of the sum of the squares of instantaneous values over 1 positive cycle and
1 negative cycle, divided by the full cycle time, the sum itself is 240^2
= 57,000 V^2, no? If we eliminate one of the 2 cycles, the sum is 57,000/2
= 28,800 V^2, and the square root of that (the rms voltage of the half-wave
rectified waveform) is 170 vs 120 V.

Don Klipstein says:

...bulb life is typically inversely proportional to applied voltage
raised to the 12th power. I often see 13.

So if a 120 V bulb lasts 750 hours at Vrms = 120, we might expect it
to last (120/170)^12x750 = 11.5 hours at 170 Vrms.

If we eliminate 3 out of 4 half-cycles, the sum becomes 14,400 V^2,
and the square root of that is 120 Vrms...

Nick

 

[Ulysses]

I find it bizarre that anyone would spread information
that encourages pushing the envelope, totally without reason,
while you seem to be fixated on getting the most light out
of one lamp when two would do the job, just so you can use
a smaller lens opening and get everything in better focus.

I believe the reason he is running them at the higher voltage is to obtain
the correct color temperature.

 

[Ulysses]

I going to guess its around 4amps.
Is the 10si a 60 or 100amp animal?

It's the 60 amp (I think it's rated at 63 amps) critter.

 

[clare at snyder dot ontario dot canada]

Only to folks like you who know just enough about a subject to argue. The original
paper, a copy of which I have, addresses only conventional tungsten lamps. I'm not
sure if the halogen cycle had been discovered at the time of publication.

I'm curious whether you'd find it equally interesting to note that a 4 hour
photoflood lamp and a quartz heat lamp designed to operate at maybe 2000 deg K behave
quite differently in response to over-voltage? Kinda Captain Obvious to me. It
would probably surprise you to learn that a staple of the studio in the bad old days
was the Sola transformer that made sure the photofloods were getting their exact
rated voltage while no one seems to care much about heat lamps.

PhotoFloods are basically the same as an overvoltaged standard
incandescent to start with. VERY fine filaments, extremely shock
intolerant. A 4 hour photoflood is running very close to it's
self-destruct level in everyday use, while the heat lamp is running
closer to the low end of it's envelope.

 

[[email protected]]

While you are right about a resistance device only
failing when current is excessive, but the fact is,
current increases with the square of the voltage.

Really?

Nick

 

[Martin Riddle]

It's the 60 amp (I think it's rated at 63 amps) critter.

Yea, it seems to be around 5-6amp for full output, 65amp. My CS-130 (100amp) requires 10 amp on the field for 100A out. Thus
90% of the output is produced by mechanical energy.



Hope that helps.

Cheers

 

[Johnny B Good]

The message <[email protected]>

I find it bizarre that anyone would spread information
that encourages pushing the envelope, totally without reason,
while you seem to be fixated on getting the most light out
of one lamp when two would do the job, just so you can use
a smaller lens opening and get everything in better focus.

While you are right about a resistance device only
failing when current is excessive, but the fact is,
current increases with the square of the voltage.

You're confusing ohm's law with the power law. Ignoring changes of
resistance due to temperature, the current is directly in proportion to
the voltage. It is power which is proportional to the square of the
voltage (or current, take your pick).

Short time overvoltage may work in some cases,
which is why motors are rated short duty and continuous
duty. A generator needs to be fully continuous duty,
so that current overheating is not a problem.

Are you willing to pay for the bulbs and field
coils that people burn out using your advice.

Good engineering means a safety factor of 2 or more,
and even with all the engineering to get the best light
possible out of common bulbs, they burn out often with
just minor voltage pulses from motors starting, and that
is I buy 130 volt bulbs, there is more to bulbs burning
out than cost.

FYI, regarding metal halide lamps, the use of a halide and a high
temperature envelope in close proximity to the filament is not to make
the filament last longer at elevated temperature, it's to allow the lamp
to maintain its lumen output over its shortened lifetime by recycling
the tungsten vapour back onto the filament to save it from depositing on
the envelope and acting as a light blocking filter.

The tungsten halide cycle relies upon the envelope operating at much
higher temperatures than possible with conventional glass to prevent the
deposition of tungsten on the inner surface. The silicate glass used
(the so called "Quartz Glass") usually operates at temperatures between
250 and 300 deg C. If you undervolt such a lamp, the cooler temperature
on the envelope will compromise this effect and, although the filament
life will be extended, the envelope will suffer blackening and reduce
the lumen output.

The reason why the tungsten halide cycle doesn't improve the filament
life is because the tungsten vapour is deposited onto the cooler parts
of the filament and its supports. The hotter parts of the filament still
erode in pretty much the same way as in an ordinary vacuum or nitrogen
filled lamp. This erosion thins the filament causing it to run even
hotter in what is basically a runaway process.

This wear mechanism is further agravated by the high current surge when
such lamps are switched on from cold (cold filament resistance being
only about one tenth of the operating temperature resistance). Since the
ever so slightly to start with thinner parts of the filament heat up
faster than the remaining thicker parts of the filament and to a
slightly higher temperature than normal, the thinner parts suffer more
loss of tungsten until they either fail at the next switch on (the usual
fate for a household lamp) or else fail several hours after the fatal
switch on event.

Such "Thousand Hour" lamps can survive several thousands of hours, if
left burning continuously and not subjected to switch on surges such
lamps usually have to contend with in a normal domestic service
environment.

Regarding the maximum field current question, there is no point in
allowing more current than the maximum based on the 12 volt excitation
voltage since this will have been set, by design, for magnetic
saturation or very close to. Additional current over and above this will
produce very little extra magnetic flux but considerably more heat.
Also, since this waste heat is a drain of power from the alternator's
output, the overall efficiency will be significantly reduced.

I seem to recall a maximum excitation current figure of 4 amps for a
12v alternator. If such an alternator's voltage regulator were to be
reconfigured to charge a "60 volt" lead acid battery and permitted to
apply the full output voltage to the field, you could end up raising the
excitation losses from about 50 watts to some 800 watts or more!
Basically, there's no simple solution to this "problem" (there _are_
solutions, but no simple ones).

HTH & HAND

 

[Ulysses]

Yes it will, don't do that! The field coils are
12 volts, period. They will take the usual charging
voltage of 14.6 to 15.1 or so, but more than that will
burn them out.

I measured 13.5 volts going to the field coil so it's looks like I'm right
where I should be.

Resistance loads draw amperage according to the
voltage applied and their resistance, higher voltage
devices need higher resistance to avoid burning out.


A separate 12 volt battery should be used to
supply field current with any abnormal use such as
this, but the output capability is more related to
the insulation rating as long as the output amps is not
exceeded.

That is beginning to sound complicated. I could tap into two batteries on
my battery bank and they in turn would be charged by the alternator that
they would be supplying the field current for but something tells me this is
a bad idea. How would you suggest recharging the seperate 12 volt battery?

A small 60 amp alternator can go to 110 volts
output (probably), but for charging batteries, the
voltage loaded should not go more than a couple
of volts over the battery rating.

The way I see it I have three choices with this setup:

1. Adjust the field current and engine speed so that it will put out the
correct Absorb Voltage with no load and go manually check it once-in-a-while
and turn it off when the batteries are fully charged. This takes a long
time.

2. Feed the output from the alternator into my OutBack MX60 charge
controller and let it adjust the voltage and current. This works well but
will not stop charging when the batteries are charged and if there's an AUX
setting that will turn off the charger I have not found it yet. When it
goes into "Sweep" mode it will (sometimes) stop charging for about a minute.
I takes (sometimes) up to about five minutes for it so wake up from it's
"sleeping" mode when I first start the charger. Meanwhile the engine is
running at full RPM with no load.

3. Adjust the engine speed and field current for what "feels" best, IOW
reduce the engine speed until the amps just start to drop a little. With
this arangement the Voc is about 80 VDC. I connected a 12 volt relay and
set the AUX on my OutBack inverter to shut off the charger when it exceeds
the Absorb Voltage. This seems to work really well. When I was using a
generator it was necessary to run the built-in battery charger in the
OutBack inverter for at least an hour at the Absorb Voltage before they were
fully charged (according to my hydrometer). With my homebrew charger every
indication is that they are fully charged when the OutBack inverter decides
it's time to act. The voltages and activation times are adjustable so it's
easy to have the AUX active long enough for the engine to stop running and
still be able to restart it right away if necessary. This is the fastest,
and probably the most effecient way out of my three choices.

And the amps should be restricted to the rating
of the alternator. Some big GM cars came with 100 amp
alternators, possibly as an option or certain models.

Currently (no pun intended) my amps are restricted by my small engine size.

 

[Ulysses]

Actually, no it isn't. The only practical limitation is temperature and in the case
of automotive alternators, the insulation is high temperature rated, class H or
above. Like your handle. Apropos.

Ulysses:

The correct answer is, "I don't know". You'll have to monitor the temperature of the
field coil as you increase the current. If you're clever you can use the field's
resistance to measure the temperature. I'll describe how if you're interested. The
cooler the operating environment and the higher the air flow, the more field current
you can run.

I'm definately interested but my poor little brain is overloaded right now.

I'm interested to hear what is in Don Young's adapter box. I've used power from one
of these gadgets before but I've never had one open. Meanwhile, through the magic of
Google, I found some info. I searched for "120 volts DC car alternator kit
-converter -inverter" without the quotes. The first useful hit is this

http://islandcastaway.com/stuff/windpower/Alternator Secrets.htm

Thanks for the link. I must be the world's worst Googler because I never
find the stuff that everyone else finds.

Go down to "Modifications". He purports to knowing what is inside the magic box.
OTOH, I quickly spotted other mistakes on the page so.... That was all I found on
the first 100 results but there is probably more info deeper down.

RE: diode voltage rating. What someone else said about the voltage rating of the
alternator's diodes was true in the past but isn't now and hasn't been for several
years. With the inclusion of more solid state controls and especially
microprocessor-based controls, two problems had to be addressed. 1) EMI caused by
the abrupt recovery and turn-off of the alternator diodes on each half-cycle and 2)
load dumps. That is, high energy high voltage impulses caused by suddenly
interrupting the current to an inductor. Typically the alternator field and the
starter motor.

A voltage spike caused by a load dump didn't matter much pre-microprocessor. About
all one saw was a momentary brightening of various lamps. Nowadays it does matter.
The industry (for sure GM and Ford and probably everyone else) addressed both of
these problems with a new design diode. It's called a soft recovery diode. When the
voltage across the diode reverses on each half-cycle, it transitions gradually from
conducting to blocking, minimizing the EMI generated.

It sounds like something bad could happen if my
field-resistor-made-from-an-old-blowdryer suddenly failed.

 

[Ulysses]

Shhhhh! Don't let the secret out.
Oops!


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
Unable to locate Coffee -- Operator Halted!

 

[Ulysses]

The message <[email protected]>




You're confusing ohm's law with the power law. Ignoring changes of
resistance due to temperature, the current is directly in proportion to
the voltage. It is power which is proportional to the square of the
voltage (or current, take your pick).




FYI, regarding metal halide lamps, the use of a halide and a high
temperature envelope in close proximity to the filament is not to make
the filament last longer at elevated temperature, it's to allow the lamp
to maintain its lumen output over its shortened lifetime by recycling
the tungsten vapour back onto the filament to save it from depositing on
the envelope and acting as a light blocking filter.

The tungsten halide cycle relies upon the envelope operating at much
higher temperatures than possible with conventional glass to prevent the
deposition of tungsten on the inner surface. The silicate glass used
(the so called "Quartz Glass") usually operates at temperatures between
250 and 300 deg C. If you undervolt such a lamp, the cooler temperature
on the envelope will compromise this effect and, although the filament
life will be extended, the envelope will suffer blackening and reduce
the lumen output.

The reason why the tungsten halide cycle doesn't improve the filament
life is because the tungsten vapour is deposited onto the cooler parts
of the filament and its supports. The hotter parts of the filament still
erode in pretty much the same way as in an ordinary vacuum or nitrogen
filled lamp. This erosion thins the filament causing it to run even
hotter in what is basically a runaway process.

This wear mechanism is further agravated by the high current surge when
such lamps are switched on from cold (cold filament resistance being
only about one tenth of the operating temperature resistance). Since the
ever so slightly to start with thinner parts of the filament heat up
faster than the remaining thicker parts of the filament and to a
slightly higher temperature than normal, the thinner parts suffer more
loss of tungsten until they either fail at the next switch on (the usual
fate for a household lamp) or else fail several hours after the fatal
switch on event.

Such "Thousand Hour" lamps can survive several thousands of hours, if
left burning continuously and not subjected to switch on surges such
lamps usually have to contend with in a normal domestic service
environment.

Regarding the maximum field current question, there is no point in
allowing more current than the maximum based on the 12 volt excitation
voltage since this will have been set, by design, for magnetic
saturation or very close to. Additional current over and above this will
produce very little extra magnetic flux but considerably more heat.
Also, since this waste heat is a drain of power from the alternator's
output, the overall efficiency will be significantly reduced.

OK, thanks. I think I understand that now. My confusion seems to stem from
something an auto mechanic once told me: there is a slot on the back
(non-pulley) side of some alternators and if you stick a screwdriver in
there it will "have full output." Well, after having taken apart my
alternator and studying what's inside the only thing I could see is that it
might test to see if the negative brush is bad. Did I miss something?

I seem to recall a maximum excitation current figure of 4 amps for a
12v alternator. If such an alternator's voltage regulator were to be
reconfigured to charge a "60 volt" lead acid battery and permitted to
apply the full output voltage to the field, you could end up raising the
excitation losses from about 50 watts to some 800 watts or more!
Basically, there's no simple solution to this "problem" (there _are_
solutions, but no simple ones).

I realize that my glowing red field resistor is wasting some power but my
bottom line is overall efficiency and so far it appears that I'm using about
25% less gasoline to charge by batteries compared to using a generator and
the OutBack built-in charger. If I can improve upon that I'm all ears.

 

[clare at snyder dot ontario dot canada]

OK, thanks. I think I understand that now. My confusion seems to stem from
something an auto mechanic once told me: there is a slot on the back
(non-pulley) side of some alternators and if you stick a screwdriver in
there it will "have full output." Well, after having taken apart my
alternator and studying what's inside the only thing I could see is that it
might test to see if the negative brush is bad. Did I miss something?

It bypasses the regulator. The regulator does NOT supply voltage to
the feild - it supplies the GROUND to the field, thereby regulating
the voltage across, and the current through, the field coil.

 

[Ulysses]

And you are using a precision voltage regulator.

Uh, yea. Sure. If it glows too brightly then it's not enough resistance.

I am glad to hear somebody is using the ordinary
car alternator in alternate energy.

A PMA would eliminate the wasted power due to controlling and supplying the
field current and I'm fiddleing around with that too. The one I have puts
out 155 VDC which is a bit too high for my purposes so rewinding the coils
seems to be the best solution with what I have on hand.

In my opinion, one 100 amp alternator is capable
of "powering" an Electric Vehicle in city driving (with
batteries and regenerative braking), and two of them
can probably power an EV at highway speeds on level ground.

How? If you are talking about using an engine to run the alternator to
power an electric motor wouldn't it be more efficient to just use a small
gasoline engine? One of the first Honda cars that was sold in the USA used
what amounted to a motorcycle engine and a chain drive. If I remember
correctly it was a two-seater and got over 40 mpg.