Alternator transformer/rectifier remote mounted (test 1.0)

[mobile_bob]

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

[mobile_bob]

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

[mobile_bob]

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

[mobile_bob]

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

[mobile_bob]

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

[BruceM]

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.)

[mobile_bob]

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

[mobile_bob]

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

[EBI-WPO]

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

[mobile_bob]

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

[EBI-WPO]

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

[EBI-WPO]

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

[EBI-WPO]

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

[mobile_bob]

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

[mobile_bob]

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