My "perky\cat/volvo" DC bat charger

[mobile_bob]

i currently don't have the capability to mount the pad mount style alternator
i can mount only the j180 style

however having two pad mount alternators of my own, one a 48vdc and the other a 52vac
i need to setup a mounting system to use to mount my alternators, and then i could also test
your too.

when i will have time for that?  i am not sure.

i will take a look and let you know.

bob g

[Geno]

Interesting 8 rib flywheel, could you provide details on part number and/or web site please.

I wouldn't mind knowing where these pulleys come from either.

Thanks, Geno

[Lloyd]

Geno,

The pulley comes from NC CAT in Nebraska....I have the part number...i'll post it as soon as I find it again.

Bob..or any other EE math type.

I need some help on my math.

I spoke to KEI this morning, and it seems that they misunderstood my test request before they shipped the alt.

I requested phase to phase open voltages measured at 4, 5, 55, and 6k rpm.

But they only measured the phase to neutral voltage at at 6000 rpm, that voltage is 112 volt ac. He offered to re-wind a  new stator and run the test, I requested, I told him I appreciate the offer but no need to exercise him.

So I found a web site, that I can't find the bookmark to now....but it gave the equation of doing the math to determine the phase to phase voltage if the phase to neutral was known...

I seem to remember that it was the sq of the 3 phases being 1.732 * the phase to neutral, so that comes up to 193.98 volts phase to phase...is that correct?

I know to solve amps by ohms law....the stator ohms are phase to neutral 3 ohms, and phase to phase 4 ohms measured static. So my question is do I need to measure the ohms while the stator is at rest(static) or do I need to measure the ohms at speed(4,5,55, and 6k rpm)

I will take the alt to Blanchard and have them spin it to get the actual numbers, I requested...

But in the mean time any answers.

Thanks,

Lloyd

Ps...I measured the voltage of the alt and RMS, on my fluke,  giving it a spin by hand, gives me a phase to phase voltage near 11.5 volts ac

[Lloyd]

3 phase watts law=
w=( Vavg * Aavg * p.f. * 1.732) / 1000 = kwats

i answered one Q.

now i need find the answer of ohms..is it static or at speed??

# The conductors connected to the three points of a three-phase source or load are called lines.
# The three components comprising a three-phase source or load are called phases.
# Line voltage is the voltage measured between any two lines in a three-phase circuit.
# Phase voltage is the voltage measured across a single component in a three-phase source or load.
# Line current is the current through any one line between a three-phase source and load.
# Phase current is the current through any one component comprising a three-phase source or load.
# In balanced "Y" circuits, line voltage is equal to phase voltage times the square root of 3, while line current is equal to phase current.



Lloyd

[mobile_bob]

if he measured 112vac from neutral to one leg, then phase to phase is 112 x 1.73, so that is correct

the losses are not stator resistance alone, there are other factors in play, reactance drops of which frequency and amperage play
a role.

first thing i would do is take it to blanchard and have them spin it to your design rpm and see what you get at about 10vdc on the
field,

better yet try to get a graph going by measuring phase to phase AC voltage at perhaps 8vdc field, 10vdc field and 12vdc field

and also at 4krpm, 5krpm and 6krpm

if you draw up a matrix, each of these tests can be done very quickly, and the results might be useful to your transformer guy
to determine what he will need to do to get you what you need for 12vdc charging.

what i would want after rectification is about 25vdc open circuit after transformer and rectifiers, at the design speed i targeted for
and with ~8vdc on the field, that will allow for some drop and some head room with the field current.

there is so many factors to account for, and because of the way that the claw pole alternator has its way with voltage drops, it is
hard to calculate what is going to happen, at least for me.

it does look like you need about an 8:1 - 10:1 step down ratio with the transformers, that is "if" the 6krpm voltage report is correct
and it is what you want to run at, and is that at full field?

if i had to make a wager, i would bet on 8:1 step down as being in the ballpark.
based on the preliminary reported numbers from the alternator builder.

i don't know anyone else that has done what you are intent upon doing, so i don't have any data to draw from.

bob g

[mobile_bob]

oops looks like you reposted before i got mine out

i had also neglect power factor (pf) as my testing has all been done with resistive loads,
but the rectifiers and the transformers will certainly skew the powerfactor as well.

at this point i think it would be best to run the matrix and fill it in with testing at blanchards

show him the matrix, and offer to write down the numbers as he runs the test, it shouldn't take
5 minutes to get all the info you want,

armed with that info, perhaps we can get an idea of how best to size everything else?

in any event i bet the transformer engineers will appreciate the matrix info as an aid to their
engineering of the transformer needed.

bob g

[Lloyd]

thank you Professor,

you know i have asked at least 8 different alt peeps, all said it can't be done... about remote rec.

then you spurred me with maybe it can be done...then you went to your own test bed and said maybe it can be done, and with some efficiency.

KEI, is the only other guy/shop that said sure we can do that...just tell me what you want...as a matter of fact we'll help you through R&D.

Then I talk with Osborn Transformer...they say no worries we can help you R&D a toroid transformer/rectifier.

i know I'm not finished..but i think that a workable system is not far off.

thanks to you and many others... i hope that this will lead to help in others co-gen projects...this concept is scalable to 24-48 volts so...we'll just wait and see.

Bob...i've said it before ...YOU ARE A HERO!


thanks,

lloyd,

[Lloyd]

Bob,

do you have the answer to the Q, about measuring stator ohms> is it static, or at speed?

i just want to know for my own knowledge....plus i want to build it into my modeling spreadsheet...so that i can compare, model against end results.

thanks

lloyd


http://www.windstuffnow.com/main/3_phase_basics.htm
Handy Formula to calculate the output of any generator at any given RPM.......

        First off 3 thing must be known... RPM, Open voltage at that RPM and the Ohm's of the stator coil.

               1. Measure the RPM
               2. Measure the Open voltage at that RPM
               3. Measure the Ohm's of the stator coil.

                Measured RPM / Open volts = RPM per volt

        To find a Desired output the formula is:

                Volts + ( Amps * Ohms ) = Open Voltage ( necessary to achieve this output )

                Open voltage * RPM per volt = RPM needed to achieve desired output

                 

                Example: Alternator spinning at 1500 RPM delivers an open voltage of 34.8 volts so....

                        1500 / 34.8 = 43.1 RPM per volt

                        The stator coil reading is .6 ohm

                         

                        Lets say we would like 14.6 volts at 10 amps from our unit

                                14.6 volts + ( 10 amps * .6 ohm ) =20.6 open voltage

                                20.6 * 43 rpm per volt = 885.8 RPM

        If you would like to know an output at a certain RPM you simply change the formula to:

                                RPM / RPM per volt =Open Voltage

                                (OpenVoltage-desiredvoltage) /ohms = Amps 

                Example: 885 RPM at 14.6 volts

                                885 / 43 = 20.58

                                ( 20.58 - 14.6 ) / .6 = 9.97 amps

                                 

        And there you have it... since, for the most part, the voltage and rpm are a constant its easy to calculate the output of any unit

[Lloyd]

bob,

You will most likely appreciate this article voltage eg a new bred http://www.embedded.com/columns/technicalinsights/171000435?_requestid=611985


white papre on 3phase trans formers
http://www.basler.com/downloads/3phXfmrs.pdf

lloyd

[Lloyd]

just some math before losses... from a TM

desired voltage 14.5 bulk charge @ 225 amps

6000 rpm / 193.98 open voltage = 30.93 volts average per phase per rpm

stator = .4 ohms phase to phase average

14.5v + (225 amps * .4 ohm stator)= 104.5 open voltage phase average

104.5 * 30.93 V per rpm = 3232 rpm estimated rpm before losses

output at 6000 rpm before losses

(open voltage - desired voltage) / ohms = amps

(193.98 - 14.5) /.4 = 448 amps @ 6000 rpm before losses

Lloyd


Just remember i'm a TM not an EE

EE = Electrical Engineer

TM = Trained Monkey

the difference between a EE and an TM is;  

A EE can make a logical deduction based on his knowledge, and even do the math.

A TM can do what you teach it to do...and sometimes seek out the knowledge to deduce the math...but that doesn't mean he's right...so always refer to an EE... when a TM does the math.

[mobile_bob]

Lloyd:

i use a totally different approach to design than Ed Lenz does, with his wind power generators
where he uses the resistance of the stator and factors it with rpm and open circuit voltage.
Nothing wrong with his formula for the alternators he designs and works with, and Ed is a heck of a nice
and very sharp fellow. (Ed from windstuffnow.com, i have known him for about 10 years now)

iirc, and this from memory

the resistance of the stator changes with increasing frequency (which will be perhaps 10x that of a typical windgenerator in this application)
increasing amperage, and increasing heating, along with a few other factors, which use several of these factors in some mix to form
different kinds of reactance.  all this works together to form "effective resistance which is likely to be dramatically different than measured
resistance of the stator at rest.

for my applications, i have found it just so much simpler to apply the stock stator in the oem alternator at the voltage, rpm, and field current
i would like to run it at, then measure the output current that it is capable of sustaining under these parameters.

from that i can determine the units suitability as used, and i can calculate what it might be if reconfigured from delta to wye, wherein
going from delta to wye my effective voltage will increase by a factor of 1.73 and the current will decrease by a factor of 0.57.

its more or less an empirical method that will get me very close to what i need in the end.

after testing in both configuration and filling in a matrix (fixed rpm, but various field currents at various loads) i can determine a performance
profile for that particular stator in that particular alternator.

i use the particular series of alternator because of the rather large number of possible stators offered by the oem, i use primarily two different stators in testing, one is from the 175amp unit and the other from a 270amp unit, the former is wound bifilar or two in hand, the latter is wound
quadrafiler or four in hand.

the bifiilar and quadrafilar stator windings keep the eddy currents down in the turns themselves, because heavy gauge wire will have higher eddy current losses within it than 2 or 4 strands of lighter gauge wire.

after having run all the tests, and filled out all the matrix i can then determine what exactly i need to do to tweak things with a rewound stator
for my specific application, i have not got that far yet.

if and when that day comes i will order the rewound stator, run another test matrix and from those three stators, (oem 175, oem 270 and custom in both delta and wye) i should be able to then produce a set of formulas that will allow one to engineer a stator for this specific
alternator core to get what one wants with some precision.

it might be when it is all said and done the formula you listed will be applicable, however i have my doubts at this time
as the alternators exhibit some non classical behavior that is counter to what i have been told by EE's previously.

in other words i am not convinced that the classical formulas work to explain the operation  of these alternators under the conditions
either you (with a transformer being fed) or by me (where i am running it a 4x original voltage).

doesn't mean that i am right, i may well be wrong, it wouldn't be the first time for that



bob g

ps. RE electric who's parent company escapes me right now, (but is located in seattle) and is a competitor to blanchard
bought out a rewind facility about a year ago in california. i was told back then that after they got the transition done
they could produce stators to whatever spec i wanted.

i figure they would have to be competitive to the oem stator in price or they could not sell them, a new stator from
leece neville is about 140bucks, so i am thinking i can get a custom done for a C note.

a hundred bucks ain't bad, if one has a good idea that his spec is very close to what he needs. so...

for me i would rather determine that spec through empirical testing rather than trust some set of formula derived from
lower power, exceptionally low hz, and often aircored alternators from the windpower boys.

[Lloyd]

Thanks Professor,

I plan on doing exactly as you prescribe. I have the spreadsheet for the matrix nearly done. When I have, Todd run the alt, I will fill in the numbers...that should give me some good empirical numbers for my model. Also depending, I have 2 more custom stators, to derive numbers from, at no costs.

I just wanted to build my model prior to actual numbers, then compare to actual numbers. I actually got the formulas from the US Navel Electricians Teaching text manual, from the 3 phase sycronis alternator chapter. I suspect Ed from windstuffnow.com, may have gotten his number from the same place, as his pages on 3 phase are laid out in almost identical order. I posted his stuff so I wouldn't have to scan the navel text.

I figgerd the stator ohms changed with speed,(I just haven't been able to confirm that with all of the design texts I have been reading) and I know the other losses also increase with speed, and temp...The temp issue is one reason I designed the sea water to air heatX, for turbo cooling. The alt will see a steady diet of 30c inlet air...which should be an advantage over the normal engine room air temp, of 70-80c.

I just don't have any way to do the load testing, my little shop is more set for woodworking...plus I'm a TM not an EE, so I don't have a shop full of scopes and things.. I sure can build a nice spice rack though.

You might also give KEI a call, they have been nothing but a joy to deal with...he's old school...and more than loves to take on project out of the box...by his own statements...and they are fair and reasonable in price.


Thanks again...I will keep you posted
Lloyd

[Lloyd]

http://dl.gmseenet.org/bitstream/handle/123456789/926/GMSARN08-E26.pdf?sequence=1

Bob,

I know this is a link that goes against your empirical design process..

but there is some that might make sense to you and others..

lloyd  

most elementary but good to TM http://media.wiley.com/product_data/excerpt/75/04716144/0471614475.pdf

[mobile_bob]

Lloyd:

i can't get the first link to load up,
the second link i will comment on...

notice page 18, fig 1.17 ?
that is the grandfather of the clawpole machine, the one i alluded to in the white paper.
thanks for this link  as that picture of the alternator now being in a museum is much higher quality than
the original grainy B&W from the google book.

i have read every last scrap on everything i can find on alternator design, and after a while one thing becomes clear
that being there is very little new that wasn't known about alternator design back in the 1890's save for improvement in materials.

the issue i have with all the engineering as opposed to empirical testing to base my decisions or design methodology, is this...

i am constrained with the built in compromises taken by the oem, and as such i cannot find out several key factors that might be
useful in altering a design.

i have no idea what the magnetic properties of the stator are, no idea of the stator inductance, the reactance of the machine
and a variety of other things that might be useful, and...

even if i knew, there is nothing i can do to change most of these things in any meaningful way, i can alter inductance to some extent
but in doing so i also alter the output voltage and generally opposite to what i need. reducing inductance is useful in reduction of reactance
but to do so requires fewer turns of copper, which reduces voltage, so i have to turn the unit faster which raises the frequency

frequency has the same effects on reactance drops as does inductance, so you see you end up chasing a problem all over the page to no
real effect.

the reason i mention this is the text and formula will lead one to believe that the predominant losses in a clawpole alternator are the reactance drops, of which increases in frequency (rpm) and inductance (more turns of copper) are the dominant factors, well...

in my testing i have found this not to be the case with the alternators i am testing, the dominant factor is current, so i have to go back and ask
why this is?

it comes down to this, the formulas that the EE use in classic alternator design are designed to explain the operation of more common
60hz alternators that have both laminated stator and rotor poles, apparently the solid clawpole rotor, the higher frequency, and lack of iron
in the stator core (as compared to a typical 60hz machine) all conspire to skew the outcome to where the classic formulas don't quite work
out in real world operation.

so that leaves me with having to explore the operation parameters of the alternators i have available, develop matrix's and run the tests, then
afterward crunch all the data in an effort to develop some formulas that explain the results.

so far i have not found any text on the design of clawpole alternators running at 400-600hz with the attending formulas

if you come across some let me know

bob g

[Lloyd]

Bob,

I'm not questioning your design style...seat of the pants usually beats books sense everyday of the week. I am hoping that i will learn something by running things parallel, pre calc & real world, in comparison. i might be a trained monkey, but I have never been able to accept that something works...I always have to know why & how...other wise I am very frustrated.

The navy text manual I have is 400hz design of a six & 12 pole.. it has the same numbers that I posted earlier off your friends page. Also I might start looking at the aircraft, bc they also use 400-600hz.

One thing I read is the wye connected will result in higher current at lower rpm, that's why many diesel engines use a wye connected. I think in both our cases that can be a good thing...the kw of a machine doesn't change by the way it's connected...

So if we connect wye out to delta delta on the transformer, it seems that, that is the ideal situation..at least in my case.

Lloyd

Try this re-link to the one that wouldn't load http://dl.gmseenet.org/bitstream/handle/123456789/926/GMSARN08-E26.pdf