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From: (no name) (no email)
Date: Mon Feb 11 2002 - 12:04:13 EST
Gene Gruender writes:
<snip>
>First, regulators don't control amperage, at least none that I'm
>familiar
>with. (Possibly one of the control systems like Heart's does.) They
>control output voltage.
Regulator technology is not rocket science.
The regulator measures system voltage and then controls the alternator
field current which is the way alternator output is controlled.
You can gussey it up with lots of bells and whistles, but in the end, the
regulator still controls field current as a function of system voltage.
>Amperage is a function of what thealternator
>is
>able to put out and what the system will absorb. This may be a fine
>point
>in some cases, but if you put a huge alternator on a system that has
>one
>small battery, you're not going to put out much at the start, and
>once the
>battery takes a little charge, your amperage is going to taper off no
>matter what the alternator or regulator is.
The output capability of an alternator and the size of the battery bank
are directly related.
The recharge rate of a battery bank is about 15%, so if you want to
recharge a battery bank at 150A, you need a 1,000A house bank to accept
that rate.
The above is just plain battery basics, documented in a lot of battery
tech manuals.
>The high output alternators have a couple advantages over the auto
>ones.
>First, they have better (maybe the right word is bigger) bearings,
>they are
>wound differently so that they can put out more amperage at lower
>speeds,
>and they have heavier wires and diodes. Of course, due to these
>things and
>the fact that they are built in far smaller quantities, they cost far
>more.
You have a catch 22 situation here.
There is more than one definition of "high output".
Alternator 1 has a maximum output of 160A @ 5,000 alternator RPM;
however, it also has a 120A output @ 2,000 alternator RPM.
Alternator 2 has a maximum output of 160A @ 5,000 alternator RPM;
however, it only has a 30A output @ 2,000 alternator RPM.
Both are "high output" alternators, but they have significantly different
performance characteristics and belt drive requirements.
BTW, alternator 1 is a stock alternator and the one I will be using.
>As to belt and sheave size, my research and talking to Hamilton Ferris
>(the
>man who owns Hamilton Ferris company), I was told that you could run
>up to
>150 amps on a 1/2 inch belt.
Strictly a bunch of "smoke and mirrors".
Without specifying operating RPM, the above is meaningless.
Given the right configuration, could accomplish the same thing with a
piece of clothes line.
>Get the best. One is Gates Green Stripe.
Gates has been the weapon of choice for years.
>Find pulleys that will run the alternator
>at
>that max speed when you motor is turning the max speed.
This will typically yield about a 2:1 ratio for gasoline engines, and
about 3:1 for most modern high speed diesels.
>It doesn't
>matter
>at that max speed, but it will get your alternator turning as fast as
>possible at low speeds without over reving it at top speed.
The other option is to buy a real alternator designed to provide high
output at low RPM.
>Comment: I don't think calculating engine horsepower required from
>amperage output is valid. First, they are two different animals, and
>there
>are lots of losses anyway, like belt friction, bearing friction, heat
>loss,
>etc. My research told me it took about 9 engine hp to make 150 amps.
>Your
>milage may vary.
Shaft horsepower vs: RPM are standard curves or at least they were when I
was in the business. It was part of my responsibilities to gather that
data and get it published.
Since the power requirements of the alternator as a function of available
engine horsepower is relatively small, assume a mechanical input
efficiency of 50% and move on.
ie: If the alternator input horsepower is 5 HP, size the belt drive to
handle 10 HP.
The real trick is working with the belt manufacturer's horsepower data
which requires making a belt tension assumption. 100#, is a typical value
which assumes 2%-3% belt stretch and subsequent re-tightening.
HTH
Lew
S/A: Challenge, The Bullet Proof Boat (Under Construction In The
Southland)
Visit: <http://home.earthlink.net/~lewhodgett> For Pictures
There are no problems, only varying degrees of challenging opportunity
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