i decided to chronicle this project somewhere apart from the white paper section, as it is a work in progress
and not a finished project by a stretch
overview of this project:
the goal of this project is to use an otherwise stock oem alternator, and to take three phase power off the stator at a higher voltage
than would be normal, transfer the generated AC over a 10/3 stranded cable some distance. this 3 phase higher voltage power would then be
stepped down to approx 12vac line to line using a transformer pack made up of 3 step down transformer connected appropriately to attain the
requisite 12vac, which will then be fed to the remote rectifier which will convert the 3 phase power to DC which will be used to charge a 12volt battery bank.
what i would like to determine is what is the relative efficiency of this system compared to a stock alternator charging a 12volt battery at normal distances and also how it compares in cost and efficiency with a stock 12volt alternator that must charge a battery mounted some 30 ft or more away.
there are lots of unknowns going in on this project, and i am going on what i have learned from research on the lundell/clawpole automotive alternator and the use of transformers that were made for 60 hz use being repurposed for use at 500-600hz.
not wanting to spend money on a project of unknown odds of success, i have chosen to use surplus parts to do the testing, and use them to
prove the concept, at the expense of having a useful operational system perhaps. if the theory of operation is good, and if what i have been told by transformer manufactures EE is correct, then the preliminary testing should prove the concept and then taking what is learned perhaps i will choose to either alter certain components or buy the ones needed to get the voltage within the needed operating range.
what i have to work with
a leece neville 4400 series 270amp alternator, @12 volts. it has the stator leads accessible from the rear of the case, and i have a remote
regulator plate on the alternator so that i have access directly to the brushes.
the transformers i am using are from APC rack mounted 1kva ups systems, i will be using three of them that have 120 volt primaries
and ~24volt secondaries
the rectifier bridges are a pair of negative and positive sets from a salvaged 175amp leece neville
the hookup
i connected a 10ft piece of 10/3 stranded cable to the stator posts at the back of the alternator, then connected the three transformer primaries
in a delta configuration, and attached the other end of the 10/3 to the transformer bank
the secondaries of the transformers i chose to connect in Y configuration, so as to get max voltage from the step down of the trans set
figuring if it were too high i could reconnect as delta to decrease voltage and increase amps later.
the Y connected secondaries i connected to the rectifier bridge, and left the rectifier open circuit for preliminary testing
test one:
i brought the plant up to rated engine speed of 1800rpm, the indicated voltage was ~40vac phase to phase coming off the stator
i would have liked to have higher voltage but settled with this for preliminary testing as i had to full field the alternator to get this much
AC voltage off the stator, the stator is internally delta connected, so later should i choose to change the stator to Y connection i could get approx
40 x 1.73 = 69.2 volts (which is probably more in line with what parts i have to work with actually need)
i checked the line current to the transformer and found it to not even read on my clamp on meter, i would assume there to be a bit of current flowing but because of the current being ~500hz the meter might not be able to accurately measure that level of power. i did not that the engine
does not change tone with power to the transformer primaries nor does the transformer cores even warm up,, so the power level used to magnetize the cores and cover core losses might be pretty low.
i measured the voltage off the rectifier bridge and it came in at ~11 volts, not high enough to charge a 12volt battery, but this is a test and i am not that lucky to have parts that work perfectly for every project.
i then placed my carbon pile on the DC output and cranked up a 50amp load, the voltage dropped to approx 4 volts, and the stator voltage dropped to about 37volts, here having a 69volt input would be handy as there would be ample overhead to cover the drop under load and not have to full field the alternator,
i checked the stator current to the primaries and found it to be ~9.5-10.0 amps with a 50amp load, here again i expect the accuracy might be off a bit at the higher hz,
by applying the 50amp load and taking it away againl, off and on, i could not tell any change in tone of the engine, it was as if it didn't see a load at all, however 50amps and 4volts is only a 200watts, even with efficiency hits of conversion it is unlikely the load would be much more than 300 watts as seen by the engine, and i am not sure i could hear a tone change with 300 watts or not.
what i have learned so far
1. i can generate higher stator voltages, (actually i have known this for sometime) and i need to reconnect a stator as Y configuration
so that i might see around 70vac phase to phase at 1800rpm engine speed (approx 5000rpm alternator speed), or
i need to change my drive ratio and increase the alternator speed or maybe do both
2. the core losses of the transformers seem quite acceptable, i was expecting to see some heating of the cores being run at 8 to 10 times
their normal 60hz operation,
3. i need to change the transformer turns ratio, in lieu of changing #1 above, that would be very easy to do with these transformers as the secondaries are wound over the primaries and are accessible so i can remove a few turns, there are 24 turns now and reducing the turn count to
16 likely would put me close to what i need, and possibly increasing the alternator rpm might get me into the sweet spot of about 50% excitation current at moderate charge current.
CORRECTION: reducing the secondary turn count will further reduce my needed voltage, so that is not a viable option, so disregard #3 above
it would appear i will be needing to confine the alterations to changing the alternator stator from delta to Y configuration, or
increasing alternator speed, and maybe both
this first test looks encouraging, and promising
it would appear that i have achieved proof of concept, and there does not appear to be any major issues standing in the way of success
i looks like the next step might be to go ahead and choose the easiest to modify change, and then run another battery of tests to determine the outcome so that i can see what other tweaks will be necessary to dial this system in.
once i have the system to where it will provide charging at ~100amps continuous at 14.4 volts, thermally stable at both the alternator and the
remote transformers and rectifier, then the final battery of tests will be comparative to determine the relative efficiency of this system compared to a stock oem alternator with batteries closely located, and also compared against a stock alternator charging a set of batteries at some longer distance such as 30 ft.
in theory the system ought to be about even in efficiency for close charging and perhaps higher in efficiency for distance charging, and it is possible it will be more efficient than either method.
well there you guys have it, the first testing i have been able to do in over 6 months, and it feels damn good to be able to do it again.
:)
bob g
after a bit more thought, i think i will do the following
i have one more of these transformers, i think i will look into carefully taking it apart
and removing turns from the primary so that i might get the output voltage from the secondary that i need
the primary is designed for 120vac anyway, and i am down to around 40vac so i could probably take off enough turns
to get my secondary voltage up to where i need it and likely improve the transformers efficiency anyway.
i think i can remove turns by uncoiling them from the center easy enough, rewrap the set and dip the finished coil
then reassemble and drive in wood wedges to secure the coil to the core.
that might be a reasonable approach, gotta think about this a bit more.
i suppose another approach might be removing the secondaries and rewinding them with more turns of 3 or 4 in hand gage wire
to get what i need as well, i might be able to do that without disassembling the core.
yes more options
bob g
well i took the option of reducing turns on the primaries, and decided to use my spare transformer as a guinea pig
lesson learned, there are about a million laminations in one of these transformers, E/I laminations about .008" thick which is about
half the thickness i was expecting.
took all of an hour to seperate the laminations, and remove the primary winding, it is very thick rectangular section and came off like a big
soft spring, so when i am done with the primary alteration it should spool back on without a lot of problems.
i think i will finish the mods to this transformer, and see how it works and how much more time i will have invested in it, i am thinking probably 2.5 hours per transformer will be about right,, and as far as i am concerned it doesn't make economic sense to do so.
somehow this is much more difficult that i remember it being when i was a kid?
of course everything cost less, ran faster, was easier and bigger all those years ago, from memory
:)
bob g
Great progress, Bob! It could be worse- if the transformers were toroids, imagine the fun unwinding and rewinding each turn. I can't redo a primary on a toroid anymore.
I hope your transformer primary mod. goes smoothly and you get your voltage right on. An extra tap isn't cheating, if you have room for the extra loop leadout.
I hope you won't pay later for your project fun today!
Bruce:
i can't even imagine rewinding a toroidal transformer :o
as it is, it took me about 3.5 hours to comeplete the rewind of the primary of this unit
and i am now faced with doing 2 more to get a set for the 3 phase project.
good lord 10.5 hours for a set of three transformers is either a labor of love or insanity
i am thinking it is the latter.
it went surprisingly smoothly after i decided on the amount of turns i should remove from the primary
and yes i considered using taps, and probably should have!
if nothing else taps would have made the unit useful as a battery charger for single phase source had I decided not
to rewind two more.
i guess i can justify the time requirement as being an educational event, yes that is what i will tell myself!
later this morning i need to dig out my variac and apply 30-40 volts to the new primary and see how many volts i can get off the secondaries now
i am shooting for 10.6 vac with approx 35 vac input.
hopefully i am close, i think i should be or rather
i will always think it should have been right!!
:)
at this point i think it might have been much easier to reconnect the stator of the alternator as Y from delta, i have an extra 175amp stator
and the way they made it, it can easily be connect either delta or Y, because they attached ring terminals to each end of each coil and pair them up to the stator posts for connection to the rectifier.
i think before i invest more time in rewinding the other two transformers i may well reconnect the stator and do another test run to see how things play out, i suspect that would be a much more expedient means to an acceptable end, given i am not looking for a very high power use, but rather an outline on how to accomplish this goal , as related by our friend Lloyd.
his need for the transfer of large amount of power over 30ft for 12volt battery charging is something that i would find an easier work around, like
moving the batteries much closer to the charging source, however i realize he cannot do this and i suspect his application might not be the only one where such distances are involved.
all said and done, with some good testing to document the results, this work will end up as an addition to the white paper already published here, and in the end the hope would be, we all should have a very good idea of what can, cannot, and maybe even what should not be done with automotive alternators.
it feels really good to have felt good enough to actually get something done out in the shop sunday, it was the first time i felt able since about june of last year.
my how time flies when you feel like crap!
thanks Bruce for your comments, it is always appreciated
bob g
a working sketch of the system
bob g
I agree, Bob, it sounds like you'd be better off converting the alternator end for testing purposes. Over ten hours of rewinding is a bit much!
test #2
i opted to replace the stator in my test mule (leece neville 270amp) for a 175amp stator
reconfigured for Y from the stock config of delta
the open circuit phase to phase voltage came up to 99vac at full field and the DC side settled in at ~25vdc
this gives me plenty of headroom to work with, by application of load and regulation of the field down from full field.
the quick and dirty load test returned the following numbers
DC output at full field and 100amps @ 13.5vdc
AC voltage at full load 90vac, AC current phase per phase 18amps
now we are starting to get dialed into the ballpark of what is needed.
transformer presented no odd sounds, no smoke and no heating, and the 10 gage 3 conductor SO cable looks to be adequate to
transfer this level of power.
i think i could pull significantly more current from this setup, but my old carbon pile needs serviced and it is not really the right tool for continous
load testing, in later testing i will insert a fixed resistive load that will handle a continuous duty requirement.
the next step is cleaning up the rather crude breadboarding to the point that i can apply a fixed load and do some comparative efficiency
tests
so far i am getting more and more encouraged, it is pretty cool seeing 100amps being transferred on the equivalent of an extension cord
and have 13.5 vdc which is adequate for this test to actually charge a battery, the voltage climbs well as the load is decreased. i plan on
producing a graph showing amps vs voltage soon as i get things ironed out a bit more. i also did not notice any change in engine sound indicating
and increased load, which tells me the efficiency ought to be pretty good, 13.5 x 100amps is a 1350watt load plus transformer losses, rectifier losses and alternator losses, i would have expected to hear the engine change tone if the overall efficiency was typical of an automotive alternator
used as designed. if the system was 50% efficient as automotive alternators often are, then to have 1350 watts at the user end i would have to produce 2700 watts of power from the engine,, that would cause a decided change of tone with the engine.
going out on a limb here, i think the system might be at least as efficient as an oem alternator, and not take a hit for the transformers.
i know that is not very scientific, but i see it as an indicator that the path i am on is getting a bit smoother.
more to come
this is getting to be very interesting indeed
on a side note, i think these apc ups transformers are very high quality, and my bet is one could build a nice battery charger with one or two
for an st head, or build a nice 120 or 240volt welder capable of doing some decent work probably adequate for most diy'ers projects.
bob g
Wow, Bob, that was fast work on the alternator delta wiring mod and retest. Looking forward to seeing how your efficiency data turns out.
this particular series and type of alternator makes changing from delta to Y a breeze
both end of each of the three phase coil have their own eyelet soldered on, so you can connect
them as you wish if you are careful to insulate, tuck and secure the neutral connection of the Y
all told with R/R time probably less than a half hour, and i was up and ready to run again.
truth be told i needed to make the modification anyway for some other testing i wanted to do, and i got
the info i needed from this #2 test that will aid me in determining what the outcome is likely to be for that test.
funny how more pieces of the puzzle (data points) make predicting outcomes much more accurate an endeavor.
bob g
Bob, are you using your Balmar to vary the field current? If not, what? I'm up to that stage in my battery charger project. I did some testing last night with mixed results. I'll post them on my thread when I sort things out a little more.
Thanks, Geno
yes i am currently using a controller that is similar in function but made or marketed by Hehr
it does the same thing, but has pots to adjust rather than programming,
in the end i will probably use another balmar, but don't like risking one in development stages of a project.
bob g
Quote from: mobile_bob on February 15, 2010, 05:31:01 PM
and the 10 gage 3 conductor SO cable looks to be adequate to transfer this level of power.
Most data indicates 10ga wire is safe at 30A, if you are pushing 100A, (3x limit) I think you WILL get a suprise, unless it's on ceramic post & tube insulators.
It's three phase power, Mike, so each wire is carrying 1/3 the current- and that's the current at higher voltage, much less than 100amps. That and the improved efficiency of the alternator at higher volts is the beauty of Bob's design.
the 100amps comes after the three phase transfomer step down and rectifier bridge
basically this thing is a three phase battery charger being plugged into a 3 phase 500hz wall socket (the alternator)
just as a battery charger from sears might pump out 100amps to charge a battery, it does not draw 100amps from the wall socket
but a small fraction of that amount.
also after giving this more thought, and getting some guidance from my favorite EE forum, it would appear i am drawing ~2400watts
over the 10/3 line, but a large percentage of that is reactive power which i need to address with capacitors because my powerfactor
is probably not at all good feeding transformers.
also 500hz is a difficult thing to measure amps with a clamp on meter, likely not very accurate, so
i will probably choose to push ahead to test #3 and just do comparative BSFC testing to see how the system compares with a stock charging
system, the reactive power for the most part will not be a factor and i can then deduce what the actual current is, and calculate the reactive power from that.
sort of a back door maneuver, this should give me a data set to compare with, so that in test #4 i can use Bill Rogers simple method of power factor correction, monitoring voltage for increase which i can do with a voltmeter no problem and not worry about measuring actual amperage.
(or reduction thereof)
got a ways to go yet,
bob g
Bob g,
When you are getting into high frequency stuff, things get more critical and more lossy.
1. length of cabling between source and load and type of material. High frequency stuff tend to have short wirings between source and load to keep inductive losses and inpendance losses low and rectify 500Hz to DC immediately at the source or short from the generator itself.
2. type of transformer becomes more different and specialized above 100Hz. You're going above 500Hz means different windings and type of core material etc.
3. Construction of copper core (litz or solid, copper or aluminum etc), cabling type does matter as well. Some impedes the 500Hz worse than other.
Cheers, Wizard
Quote from: BruceM on February 16, 2010, 11:23:52 AM
It's three phase power, Mike, so each wire is carrying 1/3 the current- and that's the current at higher voltage, much less than 100amps. That and the improved efficiency of the alternator at higher volts is the beauty of Bob's design.
Got it, I was thinking 100A at each phase !
Wizard:
thanks for the input, let me address each as best i can
1. while this is generally true, submarines, aircraft and a few other applications use 400hz at some distances, but i am learning about inductive
losses and all the rest, and am going to try to quantify as best i can these losses.
2. transformers: a few year ago while doing early research on alternator efficiency and the use of transformers, and also being familiar with delco
and leece neville transpacks, i decided to call a few transformer manufactures and talk to their EE's they told that for my purposes the use of 60hz
transformers could be used to 400hz no problem and upwards of 1000hz before things start to drop off. i was assured that at 5-600hz i would see no
appreciable drop in efficiency using a 60hz tranformer.
higher frequencies require thinner laminations, 60hz generally use .014" thick, the transformers i am useing have .008" perhaps not as thin as i would like but a step in the right direction. the magnetizing current is ~.1amp and they do not warm up at all, so i don't think that 500hz is a problem at least that i have an indication of.
3. i am using stranded 10/3 SO cable, only because that is what i have on hand, i suspect there are losses in transmission, but so far i have not
tested/measured to determine what those losses are. i suppose i could place a meter at the alternator and another at the input of trans pack
to see what the drop is in the 10/3?
this project is a learning experience for sure, and the system would not be my first choice, as i would rather get my batteries as close to the
charging source as possible, however i realize this might not be an option for some folks, Lloyd being one.
until i run the BSFC test to compare against an ordinary charging system (12volt alternator going directly to a closely located battery), i can't say for sure whether it is a viable system or not.
it may well turn out to be better to generate high voltage DC, transfer it over the required 30 odd feet, feed an mx60 or similar and let it do the
charging.
in either case getting the high voltage from the alternator will require it to be spinning upwards of 5-6krpm which means no charging at engine idle
or low speed operation.
always compromises
bob g
got in an incomplete test run today, but ran out of fuel before i could finish
max output 125amps DC
attempted to measure the voltage drop on a single conductor of the 10/3 line, at full loading i got a it over 2volts drop
and the cable never even got warm,, but this was an intermittent short duration test, so
not much was learned other than it would appear that the voltage drop across the 10/3 in transmission due to high frequency issues
does not seem to be significant,
more testing tomorrow
bob g
got some fuel and had just enough time to run a quick test
voltage drop at max load on one leg of the 10/3 is just under a half volt
i think that is acceptable.
what i am now researching is how to accurately measure amperage on a three phase line that is running at 500hz.
i am not convinced that my clamp on is at all accurate at high frequencies, relatively speaking of course (500 being about
8 times higher than 60hz)
this is not something that is addressed in just any old book, so i have to do some digging.
bob g
How hard would it be to measure the rectified DC and work backwards to get the 500hz AC current? Or are you looking for more precision?
Kevin
i could work backwards if i knew the efficiencies of the rectifiers, and the transformers running at 500hz
without those numbers i can't calculate the ac current.
but i am getting closer,
its like formulating a logic problem, taking all the data i have and then arranging it into formula's to get those numbers
i can't directly measure.
after doing a relative BSFC test, i think i will have enough data to build enough formulas so that i can determine the AC current
and the efficiencies of the rectifiers and transformers to a fair degree of accuracy
bob g
Efficiency of rectifier isn't a problem is it? Measured voltage drop across diodes and DC current gives losses in watts. Maybe I'm missing something. I haven't thought it through.
Should be able to find published losses of running 60hz trans. at 400hz that would get you in the ballpark with a little interpolation.
Good luck. I'm just thinking out loud.
Kevin
not a problem, i like it when people think out loud
the problem with the transformers is even if i knew who made them, which i do
contacting the manufacture about specifics of the operation of the units is a
secret bound by contract.
i have been down this road before
the transformers are salvaged from APC ups units, where the oem contracts out to a transformer
manfacture to custom build units for use in their ups design, the transformer manufacture as part
of the contract is bound to never release specifics about the transformers.
however, i am glad you mentioned this, because i will try the transformer manufacture to see if
they too are bound by a similar contract.
my bet is they are, but it cannot hurt to ask
bob g
ok, this will probably be the final test of this system, by me
i have found out what i wanted to know, and here is a rough draft of the results
when i get some time i will compile what was done and attach it to the white paper section of the forum
final test 2/21/10
alternator 175amp leece neville, stator reconnected as Y from the oem delta configuration
alternator test speed ~4850rpm
field current 14volts @ 5 amps
stator open voltage phase to phase 99vac
stator voltage under full test load 85vac
transfer line from alternator stator to remote transformer/rectifier assembly = 10/3 SO cable
length of cable 6ft
transformers used 1.25kva transformers salvaged from APC rm1000 ups systems,
3 were used configured in a three phase setup with delta connected primaries and Y connected secondaries
rectifier bridge stock leece neville 3 phase bridge mounted to breadboard
load nichrome high power resistor
engine speed 1800rpm
engine started and brought up to full operating temperature, and stable operation
apply field current to alternator and measure dc output voltage and current to power resistor load
15.1 vdc @90amps, 1359 watts
fuel consumed per kwatt hour 1294 grams
comparison test load on st head
1300watts, 984gr/kwatt/hr
note: for those that want to analyze the BSFC of this unit, please note that this unit is a trigenerator driving several components
electric waterpump, electric fan, 555 alternator for starter battery charging etc, and the full load output is approx 7.2kwatts from the st
head, all generators in this class will have similar poor fuel consumption numbers being run at very light loads,
from earlier calculations the st head works out to be approx 78-80% efficient, for the sake of ease of illustration
we will accept it as 80% efficient
so with the alternator consuming 1294gr/kw/hr and the st consuming 984 gr/kw/hr under similar loading
984/1294 =.76
80% st efficiency x .76 = ~61% efficiency for the alternator/transformer/rectifier
from leece neville the alternator under full load is approx 54% efficient, so it would appear there is some improvement in
efficiency using the transformers to allow the alternator stator voltage to remain high, the alternator is much higher in efficiency
at the higher voltage and with the use of the transformers as a load matching device there is ample increase in alternator efficiency
to cover the losses associated with the transformers.
other observations
the 10/3 cable carries ~13.2amps per phase or approx 13.2 x 1.73 = 22.83amps
22.83 x 85volts = 1941watts
1359watts output / 1941watts input = ~70%
therefore the difference in the 70% and the calculated 61% is likely attributed to rectifier losses predominately
(also it is fair to note that my clamp on meter may not be accurate at 500hz measuring the AC current per phase)
more...
the 10/3 cable remains cool to the touch, as do the feed wires to each of the transformer primaries
the rectifier heat sinks heat to approx 155 degree's F, and would be cooler had i placed a fan on them
the transformer secondary windings got to 126 degrees F after several tests, without fan cooling so it would
appear there is no heating issues with them.
the alternator stator gets quite hot at ~240 degree's F, i should also note that i am using the wrong rotation fan
and there is likely not enough airflow for this operation, while 240F is within the alternators capability the higher temperature
reduces the output and efficiency of the alternator.
conclusion
i think there is more that can be done to optimize such a system, using transformers better suited to this type of operation
likely would improve the overall efficiency a bit, as would a better rectifier, and an alternator with a stator optimized for this
type of service, along with a proper cooling fan.
it would appear that there is no reason why an alternator cannot be used as a 3phase generator of AC current, transfer the power
some distance at higher voltages, then step it back down and rectify for battery charging, and in doing so not suffer losses in efficiency.
it is also likely in my opinion that the overall efficiency could be improved as well.
while there may well be some flaws in my testing procedures and measurements, it is my opinion that the rubber meets the road in
how many grams per kwatt/hr the engine burns to produce the intended voltage and amperage needed to properly charge a battery bank.
i think my numbers are good enough, the estimate of system efficiency being approx 61% is likely within +/- 2 points, and in any event
the results illustrate that the system is certainly as efficient as a stock and closely coupled charging system and likely higher in efficiency.
certainly there appears to be adequate promise with the system that ought to warrant further R&D by someone that is interested or has
a real need for what the system offers.
bob g
i wanted to add the following
the alternator stator connections i modified from delta to Y
the voltage goes up 1.73 time, but the amperage goes down by the reciprocal
or about .57
so for an alternator that is rated originally at 175amps it would then become rated
at 175 x .57 = ~100amps
the oem rating is based on 77 degree's F, and is the cold rating
the hot rating is ~145amps originally, so
145amps hot x .57 = 82.65amps
about 83 amps should be the max rating for the stator, we are drawing approx
13.1v x 1.73 x pf = 22.66 amps assuming pf of unity (which it is probably close to at full load
on the transformers)
from an amperage standpoint, the alternator is well under its rating of ~83amps at ~23amps
i am thinking that my next move before i abandon this project will be to get an accurate measurement of the
alternator output amperage at the 500hz operational speed.
i am not convinced that i can accurately measure this high of power in hz with a clamp on amp meter.
bob g
ok, so i can't seem to help myself
like a dog on a bone, i had to try again today
this test i ran with the field at 75% approx excitation
the results boil down to an overall efficiency of 64%, as opposed to the st head being approx 80% efficient
there might be a bit more that can be found by a bit more tweaking, and i guess i will always wonder "what if"
if i don't take the time to try everything i can think of while it is setup.
what i should probably do is run a battery of tests at various loading and plot a graph of output power vs fuel consumption
and then work to determine if there is a sweet spot where the efficiency is markedly higher than at full power, it would appear
that this is likely the case as the efficiency improved approx 2 points by running at ~75% excitation.
if i had to guess, i would bet that the alternator is more efficient than the st head at high voltage, by a significant margin.
btw, i checked the alternator dc posts which are fed by the internal rectifier bridge with updated diodes, (which i am not using
in this test) the open circuit voltage is 147vdc at full field.
with enough resistive load i should be able to test the efficiency of the alternator apart from the transformer pack by retesting
with the dc output feeding a dc load at ~120vdc and measuring the amperage
that might be interesting, because i could then calculate the efficiency of the ups transformers i am using in this application (500hz)
so i guess i am not done yet :)
bob g
i believe the system will return similar results over a longer distance at the current voltage, and certainly would work
over a quite long distance with higher voltage, at least i would think.
i found a longer piece of 10/3 and am going to put in it line with the system and retest to see if there is any degradation
with increased length.
not sure i would use this system myself, but
the lessons learned here will likely find application down the road.
bob g
ps. just dug out the 10/3 and measured it at 40ft
will try to get a test in today using it.
actually i am kind of excited to see what the results might be.
yes i have seen this recently on either a bosch or a denso alternator
iirc it was a denso
the 3rd harmonic is useful on higher speed alternators, but goes away at low rpm
in my testing since i am running at near 5krpm there might be some power available
there, and i plan on doing some testing to find out.
i just wish that i would have brought out the center connection of the Y stator when i had
it apart, it would be easy to add another pair of diodes and measure the current provided by this phenomena
this testing thing can turn into a full time job!
:)
btw, i don't think you will find any of the 3rd harmonic and 4th diode set in heavy duty alternators because they
are almost exclusively delta connected stators and have no center connection, and turn too slowly in use to have
much of a 3rd harmonic anyway.
bob g
just took the time to connect the new transmission cord from the alternator to the remote trans/rect pack
turns out it is a 12/3 forty foot section of SO cable
it carries the load just fine, 13amps at 85volts under load
with a load of 14.5vdc and 85amps resistive on the rectifier
i measured the voltage drop on one of the 12 guage conductors and it measured .85vac drop over the 40ft
this is turning out to be a useful experiment.
i would have never guess i could generate and transmit power 40ft, and have 14.5 vdc at 85amps from an alternator
that would be rated at approx 85amps in stock oem configuration, and do it with a significant gain in overall efficiency.
doing so with a 12/3 equivalent to an extension cord rather than 4/0 battery cables and fight with getting enough voltage
to properly charge the battery bank.
in my opinion we are about 90% there, the next step would be to scale up to a larger capacity alternator and work out the details
the cost of this system for the crafty DIY'er would be a small fraction of what 4/0 cable would be.
this looks very promising in my opinion for those generating power some distance from their battery bank that is 12volts,
there is likely some gains with both 24 and 48volts as well but maybe not as dramatic as with 12volts.
Lloyd i think you can get the job done with a little work, and have a system that fills your needs.
bob g
talked to my biz partner and he has another section of 12/3 approx 50ft
he is going to bring it by over the next few days, i will add it to my 40ft
and try a test at ~90ft
i suspect it is going to work just fine.
this afternoon i am working on test procedure to determine the actual efficiency of the transformers at 60hz
and then at 500hz.
never know what we will learn from all this
the odd thing is, when i got to thinking about this project
the use of transformers on an alternator stator is something i have been wanting to do for the better
part of 30 years, just never did it because of being told that "it won't work, the losses will be too high"
well apparently it does work and the losses are manageable and look to be offset by the increase in alternator efficiency
that we gain by allowing the alternator to run at much higher voltage.
more later
bob g
took a bit, and i am not sure quite why, but
i managed to get the efficiency of these ups transformers
at 60hz and ~3/4 load, they are 92.4 or 92.25% efficient depending on which method you wanna use.
i am having issues with my clampon meter so i was unable to do the 500hz test, maybe in the morning when i
find my fluke meter.
i was finally able to determine the efficiency of the transformers at 60hz, by attaching two of them back to back
and use the killawatt to measure watts in and watts out to get the total loss of two transformer, divide by two
to get the loss for one transformer and do the power in/power out calc's
these transformers are much more efficient than i would have guessed
bob g
my biz partner Mark dropped off a 100ft length of 14/3, so it looks like sunday i will give it a whirl and see
if i can transmit the power that distance and still get 100amps to the load, without heating the 14/3 or suffering
high line losses.
should be interesting to see what comes of this
if i can transfer that much power over that distance, it would certainly beat the hell out of running huge cables
over a 200ft circuit.
bob g
Llloyd:
thanks for passing on the info
good to see someone is still alive there huh?
having those number from them is also useful
it gives me a very good idea what stator they are using.
there comment on the electrical noise is interesting when it comes to remote rectification
i wonder how much of what they see is due to inherent issues of long distance high power transmission or
the transformer effect of noise from their controllers being superimposed on the 3phase AC output?
bob g
apparently the shielding might be an issue with 400 plus hz cable runs
everything i have read so far tells me not to put the transmission cables in steel conduit
maybe because of induction losses?
i have no idea if the braided sheathing would exhibit a similar problem?
only reference i found was to run the cables in pvc conduit.
i guess that is another test that needs to be done? i don't have any conduit long enough to find out
for sure, but i do have a cheap am radio i can chase around and see just how gnarly the emi might be.
i am not sensitive to emi, but i know lots of electronics are or can be effected to some level by noisy line emissions.
amplepower talks of using a loosely coiled ground wire twisting over the outside of the cables as being beneficial
over long high power dc cables to attenuate the ac that is superimposed onto the dc carrier.
there are so many considerations one has to make when he steps out of the safety of the "box"
:)
bob g
There are only two noise sources, and one likely susceptible signal. This is a straightforward situations as far as good EMC design is concerned. (Sometimes it is more complex and trade offs must be made.)
The PWM drive of the regulator is one source, the diode bridge is the other. I've explained how to deal with the latter cheaply and effectively via metal film caps in Geno's charger thread. For this higher frequency, I'd cut that to about 0.02 uF.
The PWM regulator will radiate directly back on the 12V supply to it most strongly. Just a 1000uf electrolytic capacitor at the 12V supply to the regulator will probably be sufficient for a first attempt.
There will be some EMI on the AC output, picked up from the PWM excitation of the rotor and some brush noise. I'd leave it alone on the first attempt. (Small caps across each phase later if needed.) Snap on Ferrites can be useful for very high frequency problems- which you can only guess and try if all you have is the AM radio or other broadband EMI sniffer.
If the 12V supply line to the regulator is still a "screamer" on a Radio Shack 12-586 AM radio or other favored "near field sniffer", then I"d go to an PI filter with the power (powdered iron toroid) inductors selected for the max current of the regulator. A Pi filter is cap, inductor, cap. In this case, with ceramic caps in parallel with electrolytics. You can also buy a stock DC filter from Powersolutions.com.
The AC power cables should be twisted (all three together) via drill. Then you could use steel conduit and not worry about inductive heating. (PVC should be OK) If the shielded cable Lloyd mentioned is already three conductor, round, with a "lazy twist" of 1 turn or more per foot, that would be great.
The 12V power run to the regulator should be a twisted pair to the battery bank or buss- NOT using some ground buss separated from the positive supply. The 12V battery sense should be a shielded, twisted pair. Yes, a pair. If the regulator doesn't have a ground for the sense cable, find the ground on the board near the input and make the connection there via your own pigtail (or at the supply ground if that's close).
If you have any questions as to the why's of each of these elements, just say so. As I said earlier, this would be considered the "obvious" good EMC design. I find that it isn't worth wasting your time on "what you can get away with", as a system which is glitch prone is a nightmare, and withing reason, who want's to spend a bunch of time to save a few bucks.
In the automotive industry or other very high volume situations are a different and interesting situation. There a dollar saved is 10 million in profits or more, and the corners of solid EMC design are mercilessly cut. $100,000 in engineering and testing to support those cuts considered well worth it. Auto electronics engineers do some amazing work in a brutal physical environment and even more brutal budget. (I worked for Motorola on a special assignment with another R&D manager evaluating needs and development methods and designing a new set of embedded processor development tools for Delco in the 80's, I'm not blowing smoke.)
test #3,943
:)
or so it seems!
i started out doing some cleanup, that went well enough
then grabbed the 100ft of 14/3 SO cord and found it to have nicely sealed on plug ends
now what am i gonna do with that?
of course i didn't cut the ends off, so i dug around and found another section of 12/3 and but connected to my 40footer
for a total of 90ft
no problem at 500hz, about a 2volt drop across any one of the 3 conductors which i find acceptable enough
no heating or other issues apparent.
what i didn't do was run a radio test! i completely forgot!
guess i will try for that one in the morning.
i did find a 3phase contactor with a 120vac coil, connected it in line to switch the 3phase 500hz 99volts per phase
to the transformer pack, and attached a cord to the contactor relay coil and plugged it into the st head for kicks
that way when the engine starts there is no load on the alternator until the engine comes up to speed and the st
starts to make power, then the contactor is closed and charging begins
this is not a method that i will be using full time, just something that makes testing easier when you only have two hands.
more later on this
Bruce: thanks for the input in re to emi and all that stuff, i am thinking what would really be nice would be a short white paper
on the subject explaining different methods of mitigating this issue.
bob g
i would be tickled pink to have a half controlled three phase rectifier, for DC use only
let alone 6 or 12 rectifier controlled by timed firing to reconstitute a 3 phase waveform.
that brayton unit has been really fascinating to read about, having read several reports
there was lots to be learned from nasa on that one.
any alternator that can turn 40krpm plus and have ~97% efficiency is pretty cool indeed.
bob g
Bob,
When the 4th diode rectifier was mentioned in an earlier post, I knew I had seen it before. My 96 Ford Service manual shows that it is used on all Ford alternators as of then. Interestingly, going to the Diesel section, the 215 Amp Mitsubishi alternator appears to have Dual rectifiers, as well as Dual wye stators in parallel. What is missing from the PDF is any connection to a field,..... permanant magnet???? Imagine the possibilities of re-wiring 2 stators to series or parallel wye or delta or....
1200pdf=standard ford alt.
1201pdf=diesel standard
1202pdf=dieselHD
Terry
all three pdf files illustrate the field/rotor coil, and yes they are all N type alternators
in that the field is supplied with B+ voltage, and the regulator pwm/switches the ground
circuit to control the field.
i was not aware that ford used the 4th diode set for the 3rd harmonic,
what is not clear to me "yet" is whether the use of the 3rd harmonic is "free" power or has a fuel consumption component
of its own, and if so is it on par with the other 3 phases in bsfc in grams per kwatt produced.
bob g
Lloyd,
On the Ford alternators, the regulator is mounted to the brush holder but can be seperated (isolated as well) easily. As the brush holder is easily removable, this can be done without manhandling the alternator or even dismantling it. The regulator as is, is a grounding type (regulates to ground) but the field terminals are isolated from everything easily so could be managed in any configuration.
The Mitsubishi is not the same though, but I cannot say for certain.
http://www.alternatorparts.com/dual_rectifier_big_ford.htm
Terry
Bob,
I guess you're right about the 1202PDF. The "coil" to the left of the regulator must be the depiction of the field. The others just show the "F" and "A" connections that are at the brush holder/Regulator junction, which is what I didn't see on the Mitsubishi. DOH!!!
Terry
Lloyd,
As I just posted, this is a field type alternator. The price for these in Rock Auto is in the mid to high $300 range.
I could see some reference to the Mitsubishi in my service manual, and the few pics show the "claws" of the rotor as being extremely wide, supporting the dual stator construction.
Terry
do they actually have dual stators? or are they dual wound and separately rectified?
just curious, always like to see how other manufactures do things
not much new under the sun and all that, but there are sometimes some interesting twists.
most heavy truck alternators are delta wound of heavy single conductors, up to about 160amps or so
then they dual wind, two in hand, at about 175 up to over 200 somewhere,
at some point up the range the quad wind, 4 in hand, my 275amp and 320amp alternators are wound that way
and have 12 diodes, basically doing the dual bridge rectifier thing.
i am considering a custom wound stator with hex wound stator, 6 in hand for better slot packing, lower resistance,
and more output in the range needed for 48volt charging. its a lot of work winding these stators, so i am going to give that
a lot of thought after i complete all the testing with what i have. recently i found i can get custom wound stators to my specs,
so i might avail myself to their handiwork. a new stock oem stator for a 270amp alternator is about 145 dollars my cost, so a custom
should come in less than that, and if it is less than a C note i know i won't be rewinding myself.
always fun.
bob g
yes i am familiar with the eco alternator
interesting concept, that was heavily hyped a few years ago
i see they are reporting more responsible numbers these days which is good.
do they offer a 48volt version?
bob g
"it ships tomorrow"
"IT" ????
oh boy, is it an early christmas present?
is it a pony?
lmao
ok, my curiosity is up, i will keep an eye on the mail lady, she and the fedex gal are getting to really hate me.
although the fedex gal now very gingerly hand delivers my stuff right to my door, after catching her
a few months ago pitching a box with 8grand worth of inverter out the back of her step van onto the pavement!
she got an ear full and an education about stuff that usually comes to my door, if it is marked fragile, "assume it is from the "ming" dynasty"
so far she has been a model citizen when it comes to handling my stuff
now if i could just get UPS to follow suit
(no chance of that every happening)
bob g
Quote from: mobile_bob on March 09, 2010, 09:59:56 PM
so far she has been a model citizen when it comes to handling my stuff
now if i could just get UPS to follow suit
(no chance of that every happening)
bob g
UPS isn't so bad. UPS Next Day on the other hand, that's a sure-fire way to get a box full of shrapnel.
Lloyd:
i like my "Torogen" design better, but as usual a parent is partial to his own creation :)
btw, i got the package today!
thanks, i think i have just the place for it!
i am going to check to see if it will fit around the catcon, i think it will, just haven't checked yet.
thanks a lot! :)
bob g
Lloyd:
refresh my memory, who is KEI?
at what cost can he deliver 220amps hot at 14.5volts?
sorry, if i don't recall, and it has been posted earlier, just been really busy lately
and too many irons in the fire.
also can he provide torque vs rpm at each output point on the graph, so we can determine
the units relative efficiency?
bob g
Lloyd:
i don't know how to advise you one either parallel or separate connected stators
i am not sure which alternator he is building on, is it the neihoff?
if he is building a 12volt nominal alternator for you, that will put out 220amps hot, that is all well
and good, but how are you going to get around the issue of 30-35ft of transmission?
or is he winding the stators for highvoltage, so that you can use transformers to step back down?
without knowing more about which alternator, how it is to be wound, its output voltage @ design rpm
its hard for me to get my head around what exactly the plan is.
got anymore details you can share?
bob g
the alternator illustrated is a leece neville product, pad mount style
it is a single stator, single rotor design, and
i am unclear as to the spec's on the stator winding, the stock stator can be connected as delta or wye, however
i am not sure what he has in mind for dual output, unless he is dual winding the stator
which is common on the oem unit to start with.
its really important to know the spec's on the stator, how it is wound, how many turns per pole, what gauge wire, number
in hand, and insulation class,, and most of all what will the voltage be at a design speed you want to run at.
what will you be using to drive the alternator with? will it be a variable speed engine or a fixed speed engine?
i have lots of questions, because i have been down this path before with other folks that get roped in on some high output
alternator only to find that it is a very poor match to their end use.
its really easy for misunderstandings to take place, and have someone sell you what they think you need rather than what you really need.
your project is outside the box in several ways, and i don't want to be responsible for recommendations when i have no control over what the builder is supplying, especially when i am totally unsure of what he is presenting.
i don't know if that makes sense of not?
btw, yes you will have to excite the alternator, it has a wound field and is 12volts, the balmar will handle that chore nicely.
bob g
Lloyd:
looks like you are on track with the builder, the only question remains what windings for what transformer
does he have a transformer pack to work with?
the leece neville 270 is wound as delta, 4wires in hand, so basically it has 4 stators connected in parallel
it could be seperated to form 4 wye windings all in parallel, 2wye and 2delta, or other combinations.
as for dual field windings, i see no advantage there at all, unless i am missing something. they would both be
wound on the common spool and work to energize the common clawpole set, so getting dual voltage would not be
possible? and in your case unnecessary anyway?
his use of 11gage wire is wholly unnecessary and might be counterproductive to getting the voltage needed to go
to the transformers.
if he has built units to be use with transformer before he ought to have a set to work with, or you might want him to work
closely with a transformer manufacture so that he can wind to fit an available off the shelf transformer or the transformer guy
can work to match what he has to work with? in the best of all worlds that is the be advise i can give you or anyone, that being
if you have a custom builder on tap, get him with a transformer engineer so that they can work together to make a matched unit.
i hope that makes sense?
bob g
it looks like the snuggy will fit the cat just fine!
thanks a lot, i owe you one.
nothing like a hot cat now is there.
bob g
no idea of their patent number, and quite frankly i would be surprised if it would be found to be useful
most of what they have is the program "code" the rest is something that is almost unpatentable anyway.
it looks like balmar makes xantrex and leece neville regulator, and probably others
i wonder what the priceing structure is from leece neville for the regulator?
guess i will have to check
bob g
yes i go back about 10 years with otherpower.com, back to their first forum
and i also know Ed and windstuffnow
both are good resources for windpower
neither can use transformers very well, because windpower although being AC is such low hz, requiring lots of iron
and those boys don't like losses at all.
here is an early collaboration
http://windstuffnow.com/main/poured_stator.htm
Ed is a very sharp fellow, and as nice a guy as they come
bob g
sorry i haven't had time to fully absorb or get my head around what it is you are trying to arrive at with the tables.
perhaps you can tell me what it is you are trying to get down to, or what it is you need to derive from such a table?
its kind of hard for me to get a grip on what your after, mainly because i am moving in a completely different direction, and
i got way too many irons in the fire so to speak.
a 12volt system is just about a whole different animal from a 48volt system, at least this is what i am finding out.
and coupled with your need for such a long distance to transmit the power,, and it is just such an odd setup that flies in the
face of everything that we strive to work against.
we move toward higher voltages to reduce losses
we put generation and the batteries as physically close as possible to reduce line losses
your system on the other hand is about the polar opposite in my opinion, and whats worse
i am not sure what there is to be learned that will be useful for the purposes of others?
add to all that your desire for ~225-250amps to the batteries
you have a very unique set of circumstances, and the solution to the problems involved are as "one off" as any i have come across.
i am beginning to think you might be better off hiring an EE to sort this one out, and help you come up with a solution that is not only workable
but reliable.
color me perplexed
:)
bob g
Lloyd:
sorry if my prior post seemed a bit stand offish, not my intent at all.
have you ordered the custom alternator with the extra stators yet?
i am kind of curious what you end up with, and how best to apply them to get done what it is you need done.
bob g
No Worries here Bob...
I started to feel like I spilled the milk on your thread, so I quietly mopped up..no crying.
I am in a final resolve...and will post it to my perky topic...when resolved.
Lloyd
Bob,
I found more of your tracks...this time over at eng-tips....
You can't imagine how many time I find your tracks in my hunt for the holy grail....hehehe
ok,
I attached a spreadsheet, which is a model that I am working on. My goal is to learn, by understanding. So if you will confirm the numbers of your... sys...especially, did you take a stator omh test, and what is that reading?
Lloyd
the stator resistance, phase to phase is probably pretty close to .170 ohms, getting an accurate measurement of a low resistance
stator coil is nearly impossible in my opinion
you reported 22.x amps ac phase to phase is actually the total current flow in the three phase circuit, rather than phase to phase
phase to phase is about 13amps x 1.73 = 22.49amps
the dc open circuit is about 25-26vc, that is after the transformer and rectifier
the dc is clamped down by the battery to 14.5vdc in testing
the rotor voltage is ~13.5vdc
all the prior is from memory, i will take more accurate numbers sunday, before i break it down for change of stator to go back to my normally
scheduled testing at 48vdc nominal
i will also come back with the calcs for efficiency, i don't recall just now what i figured it was, save for it was about 63% , but
i don't recall if that was the alternator efficiency before losses from the transformer pack or if that included transformer losses.
bob g