Author Topic: 48V alternator (ICE driven)  (Read 20618 times)

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Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #54 on: January 02, 2017, 03:31:16 PM »
That would certainly work, and so would several rare earth magnets placed around in there, instead of the bobbin winding. Whatever you decide, once the steel has magnetically saturated, there is no further increase in alternator output.  So there is no way to lower the rpm requirement for higher required voltage, at least not without rewinding the star output winding.

The disadvantage of a PM rotor would be that the output voltage could not then be so easily controlled.
Something that will work really hard then pull the charging current right back to zero once full battery voltage is reached is an absolute necessity. Its pretty important not to boil the battery !

It could certainly be done with some kind of buck regulator on the output, but that would have to carry the full alternator output power, perhaps a couple of kilowatts.  Its much more convenient to control the much smaller current in the field winding, the power required to do that is only roughly about fifty watts, not kilowatts.

Controlling the IC engine  throttle opening is another possibility, but it is not a very nice way to do it. 
And if something goes a little bit  wrong, once again you might cook a battery. 
The original automotive voltage regulator worked fine at 12v, it just needs something very similar to work in the exact same way, but designed to work at 48v.

OperaHouse

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Re: 48V alternator (ICE driven)
« Reply #55 on: January 02, 2017, 03:43:24 PM »
Not without a non magnetic shaft.

Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #56 on: January 02, 2017, 03:53:16 PM »
Yes, I see what you mean. 
It could still be done, but the steel shaft is a definite problem to be overcome for PM operation.
A permanent magnet modification would still be a backward step IMHO.

oztules

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Re: 48V alternator (ICE driven)
« Reply #57 on: January 03, 2017, 12:31:40 AM »
In practice I think a n45 neo that big would possibly saturate the shaft it would behave as a non-magnetic shaft anyway......plenty of lines left for the job I suspect

But I agree with Warp, it would be a backward step, particularly seeing how simple a regulator for it is ( in those links to playing with alts). I use a 7 dollar 7amp buck off ebay to get the 12v for the regulator to drive the rotor... works perfectly stable.... and totally controllable with a pot so you can choose your charge rate if your motor is not powerful enough to drive full power out of it when the battery is flat... and your only running a 4 or 5 hp motor from the dump.

It is not wildly efficient..... but is eminently doable for free most times.


...........oztules
« Last Edit: January 03, 2017, 12:42:58 AM by oztules »
Flinders Island Australia

Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #58 on: January 03, 2017, 01:06:06 AM »
Have to agree, anything rescued free from the tip at zero cost is definitely a bargain.

I suppose if you desperately wanted to try a PM alternator, a brass shaft might be  up to the job.
If I was doing this myself I would just rewind the field for 48v. Its probably  a 15 minute job.
« Last Edit: January 03, 2017, 01:14:01 AM by Warpspeed »

Ungrounded Lightning Rod

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Re: 48V alternator (ICE driven)
« Reply #59 on: January 08, 2017, 06:41:36 AM »

So what would be needed would be to rewind the rotor with wire of half the original diameter (one quarter the cross sectional area) but with four times as many turns.
So instead of having X turns and four amps, we have 4X turns with one amp.
Same ampere turns, same volume of copper, and sixteen times the ohmic resistance.
But we can now operate our home made voltage regulator at 48 volts output instead of 12 volts output.
Much more efficient., especially as its now only one amp required

Alternatively, if you don't mind wasting up to 144 watts (at startup, though somewhat lower during run) you can put 9 ohms of (high-power!) resistance in series with the field coil.

You might try that for a quick conversion, to get it running and test it, then rewind it when you get around to it and/or are tired of wasting the fuel to make heat in the resistor, rather than delivering it to the load as power.

Another possibility (if the alternator is wye rather than delta) is to find a point on each winding that is 1/4 of the turns up from the wye point, carefully clean off the insulation, solder on a lead, and use these to feed the regulator's AC sampling inputs in place of the ends of the wye.  (You'll also need three more 5A diodes to provide a "virtual 12v circuit ground", rather than leaving the regulator's negative terminal connected to the now-48V winding's rectifier's negative terminal, and the "alternator light tickler circuit" will need a rework.)  Then the alternator operates about as designed and no extra power is wasted.

You could also do this with external 4:1 transformers, even if the alternator is a delta (the transformers can still be connected wye), though your regulation accuracy would suffer slightly.  Get some cheap Radio Shack transformers and rewind them as autotransformers.  You'll need at least enough core to handle 48 watts multiplied by the transformer's original rated frequency and divided by the alternator's frequency at cutin.  Automotive alternators run at a high frequency compared to grid mains (to reduce the amount of core and wire required) so that's a pretty small core.
« Last Edit: January 08, 2017, 07:31:04 AM by Ungrounded Lightning Rod »

plasmahunt3r

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Re: 48V alternator (ICE driven)
« Reply #60 on: January 09, 2017, 07:54:15 PM »
I was looking at DC-DC converters on Ebay, and I noticed encapsulated golf cart 48v to 12v converters, 10A & 30A.  For around $14 bucks, you can get the 48v to 12v 10A converter and run your field coil off this converter using your 48v battery bank.  Then RPM will get the voltage you require.  Simple.
« Last Edit: January 10, 2017, 12:21:46 PM by plasmahunt3r »

bergmanj

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Re: 48V alternator (ICE driven)
« Reply #61 on: January 16, 2017, 10:08:47 AM »
Folks: Just "thinking out loud".

What about a hybrid field consisting of a ring magnet capable of, say, 50% power output excitation (or 10%, or 100%, or anything desired); and an electromagnet that would buck / boost the actual working field strength to control actual output needs?

Yes, I recognize that this would not be "fail-safe" with regards to field control failure.  but, what control scheme IS totally "fail-safe"?

This kind of hybrid field would be self-exciting, and controllable.  It could also "save" the "waste" of output power at peak loads when needed most (if, say 100% power PM excited, then countered by electromagnet at max. equivalent opposite field when no external load is present).

I know that there are probably "cracks" in this thought!  But, want to hear other's thoughts anyway.  Makes for good conversation that may continue to move things forward.

Regards,   JLB

p. s. Not on here very often due to lowly dial-up internet connection at home; am at a high-speed connection right now.

joestue

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Re: 48V alternator (ICE driven)
« Reply #62 on: January 16, 2017, 01:48:51 PM »
one way to field weaken an automobile alternator would be to stack two of the stators as in figure 7 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.569.5759&rep=rep1&type=pdf the same method is shown in figure 16.

a coil of wire in the stator is what regulates the flux density.

it seems to me you could cheaply build a centrifugal governor to adjust the phase between two sets of magnets. getting the cams (or non linear springs) correctly built to get constant volts with rpm would be a bit of a fun challenge.

OperaHouse

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Re: 48V alternator (ICE driven)
« Reply #63 on: January 16, 2017, 03:04:14 PM »
If you are willing to make a non ferrous shaft so the magnets can be installed there is no reason to add a field coil.  Electronics can be added to make it do anything you want.  I'm confounded by all these Rube Goldberg attempts to avoid electronics which in the end involve as much electronics as doing it right.

Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #64 on: January 16, 2017, 03:13:01 PM »
Definitely agree with that ^^^^

A brass shaft should not be too difficult to make.

bergmanj

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Re: 48V alternator (ICE driven)
« Reply #65 on: January 22, 2017, 09:39:06 AM »
Folks,

I've sat on these thoughts hoping that my dissapointment would wane; after several days, it hasn't; so, here goes:

I really don't believe that trying to "think outside the box" is so-called "Rube Goldberg" thinking, in the negative sense in which it seems to have been used here.  These kinds of thoughts have made actual leaps in science and technology many times over millennia.

Even if someone here should communicate something which may be initially considered by some others as being "stupid, ignorant, foolish", etc.; those ideas can be very valuable in that they may precipitate other ideas which have more practical merit.  This kind of thing happens over and over again continuously.  So, I, personally, reject the idea that "Rube Goldberg" is something that shouldn't be here.  I encourage it!

Both Einstein and Tesla (and many others throughout recorded history) were "Rube Goldberg" thinkers, according to their "society" and peers, early in their careers; yet, they revolutionized our world.

Referring to other folks' ideas here as being "Rube Golberg" just puts them down and totally discourages  potential progressive happenings on this website.  I really hope this is not the direction being taken; as, I find this whole body of knowledge very enlightening; and, with good practicable thoughts, and practical information from many directions and areas of expertise.

To a few of you: Lighten-up on those with whom you don't agree; they actually have great value here too!

Regards,   JLB

p. s. Many folks do not understand the difference between the words "practicable" and "practical": Practicable is used to describe an unproven idea which seems like it may work; practical describes an idea which has been proven to work; i.e., "Her idea may seem practicable; but, has not yet been proven to be practical."

DamonHD

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Re: 48V alternator (ICE driven)
« Reply #66 on: January 22, 2017, 12:17:28 PM »
Mmm, the UK equivalent to Rube Goldberg is (W) Heath Robinson, and to describe a machine as Heath Robinson is only mildly rude (more serious if you're the Health and Safety rep though...)

@bergmanj I may be looking at something other than the comment that's exercising you, and I agree in general with your sentiments, but I think a caution to try to keep the complexity where it is probably easiest to handle is surely a good one.  Of course, if that place is not where our skills lie, it may not be something we can do, but the principle is still good.

But tell me here or in a PM if I'm missing the point.  I may be being particularly dim having been 2 days in bed with some lurgy or other...

Rgds

Damon

joestue

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Re: 48V alternator (ICE driven)
« Reply #67 on: January 22, 2017, 01:30:04 PM »
this is another document concerning a variable flux machine.

power.eecs.berkeley.edu/publications/theses/PerryPhDThesis.pdf
page 19 shows a photo of the rotor.


very simple to build. but not so simple to get high flux densities, not appropriate for direct drive wind turbine applications.

Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #68 on: January 22, 2017, 01:38:48 PM »
Have to agree with Bergmanj, its quite frustrating when a simple idea is proven to work, but everyone  says they would rather stick with the more complex and expensive way, because that is the way it is done.

I have become famous (infamous ?) for suggesting alternative ways of doing things, that gets some people really angry.

One example is the simple analog voltage controlled solar MPPT regulator.  The idea is very slowly catching on, but I have been doing this myself for many years.  I  am told it cannot possibly work, you must use software and the perturb and observe algorithm or it is not real MPPT.

Another example is I am told PWM is the only way to build a true sine wave inverter.  Nothing else can possibly work.  I have built several stepped sine wave inverters that produce less than 2% harmonic distortion without any output filtering.  Is there any interest in this ?  absolutely none.


joestue

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Re: 48V alternator (ICE driven)
« Reply #69 on: January 22, 2017, 02:25:40 PM »
there was a commercially available inverter that did that, the reasons it isn't used frequently are many.

here's a paper on it http://www.sciencedirect.com/science/article/pii/S2090447914001099
or google "cascaded transformer multilevel inverter"

flying capacitor multilevel inverters are also a thing, as are diode clamped multilevel inverters.
the usual problems are getting the switch times exactly right so that the voltage between each step is constant. and under reactive loads you can get problems.

but the advantage of lower switching loss is of diminishing returns.
« Last Edit: January 22, 2017, 02:31:27 PM by joestue »

Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #70 on: January 22, 2017, 02:52:41 PM »
One of the biggest advantages of this is the excellent tolerance to highly reactive loads, because the inverter is fully bi directional. It handles out of phase current thrown back at it with ease, something PWM usually has a great problem with. Excellent for starting motors and nasty loads like starting multiple fluorescent lights simultaneously.

Voltage regulation is better too, because it does not require any output filtering.

I agree that for low power, its overly complex and PWM is the better lower cost solution.
But for several Kw to tens of Kw its much easier to get going than PWM, as there is no high frequency switching involved.
For home construction its much easier to build without the frequent blow ups the plague high power PWM guys.

Its not more common because the component cost is higher, its much better suited to home construction.

OperaHouse

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Re: 48V alternator (ICE driven)
« Reply #71 on: January 22, 2017, 03:49:26 PM »
Long ago I thought I saw a two voltage step MSW inverter.  Can't say where I saw it, but I remember being shocked when I first saw the single step and dead time of  MSW inverter.

george65

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Re: 48V alternator (ICE driven)
« Reply #72 on: January 22, 2017, 04:00:49 PM »
Have to agree with Bergmanj, its quite frustrating when a simple idea is proven to work, but everyone  says they would rather stick with the more complex and expensive way, because that is the way it is done.

I hear you on that! I have a YT channel where I post things I have built and how to do them and the level of " It can't possibly work because it's not expensive, enough, difficult to make, complicated in operation or have enough built in failure points, is insane. And I have to say, that sort of mentality is very clearly predominantly from Americans.
I get people from places like Brazil, agentina, especially Russia and other eastern countries and they love the ideas and some are even able to simplify them further.

So many others however acknowledge the things work well but want to go to specialist parts and fittings and a lot of trouble and expense to achieve in many cases a lesser result because it appears to make them feel more secure or comfortable.
I can't get my head around it.

Very clearly though, They can't get their head around something simple and straightforward and seem to think because it is easy and straightforward they must be getting tricked or something.

I'm ALWAYS interested in things that are straightforward and simple.

I have been looking for ways to Drive a water heater from solar panels which are less than the elements output. I have found a simple, efficient and cheap way of doing this with off the shelf components.  I was told ( and am still being told) on place I mentioned it that it can't work and people flat out didn't believe me.  Yeah well, believe what the hell you want. I'm not trying to sell anyone anything and it's no skin off my nose whether you believe me or not.  I worked it out, got the result I wanted in a way that I could build ( assemble) at a cost low enough I could set it up as many times as I wanted so I'm happy and have hot water and you are still looking for a way to do it.   :0)

Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #73 on: January 22, 2017, 04:25:17 PM »
Yes, modified sine wave inverters are pretty horrible. 
You only get three possible output voltage steps +100%  zero and -100% (three output levels).

But if you add a second square wave inverter to it that has an output transformer with 1/3 the output voltage of the large main inverter transformer, that will also give three output voltage levels of +33%  zero and -33%.
This only needs to be at one third the power level of the main inverter, so it requires much smaller components.

By turning both inverters on and off in the correct sequence you can generate nine possible output voltage levels.

zero  +33% +66% +100% +133%  +100% +66% +33%  zero -33% -66% -100% -133% -100% -66% -33% zero

Nine different voltage levels, eighteen voltage steps per cycle.
All with only two very simple low frequency push pull square wave inverters.

If you add a third even smaller inverter, 1/9 the voltage and 1/9 the power, you can generate 11% voltage steps, and have 3 x 3 x 3 or 27 voltage levels which really starts to look like a decent sine wave.

A fourth really small inverter of 1/27 the total output power, and 3.7% steps can generate 81 steps.  And it looks like a pure sine wave with just a tiny bit of ripple on it (162 ripples per mains cycle)

The voltage steps are all equal voltages, but the precise timing of the steps is what produces the sine wave shape.

Its done by storing the switching pattern in an EPROM lookup table and just continuously incrementing the address.  No need for a microcontroller, its just  basically a crystal oscillator, a counter and an EPROM.
EPROM data just switches the inverter transistors on and off as required.

Its really simple to get going.  Voltage regulation is possible by switching to different lookup tables within the same EPROM.
Over current detection just zeroes the counter, so it starts off again from a zero crossing.

I have now built several of these over the years all of which worked very first attempt and have been amazingly robust.  Whereas I have had more than a few problems with high power PWM inverters turning into smoke.
« Last Edit: January 22, 2017, 04:40:51 PM by Warpspeed »

Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #74 on: January 22, 2017, 04:51:08 PM »
Haha George, we cross posted.
You are quite right about us Aussies being very inventive, always have been and I don't know why, but it rally shocks some of our foreign friends.

Bruce S

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Re: 48V alternator (ICE driven)
« Reply #75 on: January 24, 2017, 07:55:12 AM »
All;
I was quietly asked to re-read these posts. It seems there's a mis-conception about people getting peeved about other posts.
Sure there are those who might be perplexed about why people take the long way around, but that doesn't mean they're slamming a specific person or people, if they actually called them stupid, I would've already gone into GM MODE.

This sight remains as a point for sharing of ideas, some take longer to open their minds, but that doesn't mean they are closed minded.
There are people on here who help as much as they possibly can, yet people either keep trying to go around a simple answer, those poster/helpers do have they right to vent their frustrations.

FWIW , I disagree with bergmanj, Here in the great state of Missouri "Rube Goldberg " is not only celebrated, but we actually have had contests using his ideas.
So making the statement about it being a put down is as bad as trying to call someone out about the closed minded ones being predominately Americans.

FOR those of you who've not been around for longer than a just few years, there was a fire storm that nearly engulfed every owner, Admin and Mod 1/2 decade back. Yet, as the discussion went on , the ability for people to see the other person's view got better.

I am glad that as these discussions continue, those statements have waned.

Cheers 
A kind word often goes unsaid BUT never goes unheard

OperaHouse

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Re: 48V alternator (ICE driven)
« Reply #76 on: January 24, 2017, 09:55:21 AM »
Here is an interesting alternator control.  Haven't looked at it closely.

https://birds-are-nice.me/ipfs/QmRzzZzdJsJD712naLMDUsYfwJ2ThphJvBuhLU4PTRzpp5/

bergmanj

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Re: 48V alternator (ICE driven)
« Reply #77 on: January 24, 2017, 02:34:38 PM »
Bruce,

By your standards, yes, I would have misunderstood, by standards in my neck of the woods (N. E. MN) the reference to Rube Goldberg would be viewed as a very strong put-down.  So, now maybe we all understand each other; thanks for the comments.

I was simply looking for some open-minded discussion; without any of the "that woun't work" (why? - explain, please), or, "that's too complex" (again, why? - explain please) commentary.  I certainly welcome good, honest critique; but, don't believe that seeing "negative criticism" without thought-out explanation here, is helpful to this forum.

Regards,   JLB

Bruce S

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Re: 48V alternator (ICE driven)
« Reply #78 on: January 24, 2017, 03:55:53 PM »
The hard part is getting a point across without being write there.
Flat lines without long drawn out explanations can look like an attack.
This is one of the reasons why the Mods span the globe and we have each other look at a post that could be running into flame war time.

It does look as if this has begun to settle down.
Hang in there.

Cheers
Bruce S
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electronbaby

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Re: 48V alternator (ICE driven)
« Reply #79 on: February 08, 2017, 09:48:06 PM »
Some good ideas were thrown around. Why not use a standard gen head, then rectify it, then filter it, then send it through a conventional mppt charge controller to your batteries? Pretty solid way to do it, and you can dial the current and engine rpm where you want it. Plus never worry about overcharging. This approach has worked great for me for many years, and im still using it on my listeroid (amonst other higher speed generators). The original posts from 2007 have disappeared from Fieldlines, but ive located them here:

https://web.archive.org/web/20080426031123/http://www.fieldlines.com/story/2007/12/30/15943/946

https://web.archive.org/web/20080312155055/http://www.fieldlines.com/story/2007/12/30/21440/810

https://web.archive.org/web/20080426031128/http://www.fieldlines.com/story/2008/1/2/231538/0408

https://web.archive.org/web/20091019070922/http://www.fieldlines.com/story/2008/4/15/19555/1553

The first two posts explain details of the alternator build. Ive pulled 3kw off it all day long a year ago. I built a really neat electric start system for it also. info about that can be found here:  http://www.windsine.org/2017/02/07/listeroid-backup-generator/

RoyR
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