Author Topic: 48V alternator (ICE driven)  (Read 37095 times)

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DamonHD

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Re: 48V alternator (ICE driven)
« Reply #66 on: January 22, 2017, 02:17:28 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

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joestue

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Re: 48V alternator (ICE driven)
« Reply #67 on: January 22, 2017, 03:30:04 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.
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #68 on: January 22, 2017, 03:38:48 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, 04:25:40 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, 04:31:27 PM by joestue »
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Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #70 on: January 22, 2017, 04:52:41 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, 05:49:26 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, 06:00:49 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, 06:25:17 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, 06:40:51 PM by Warpspeed »

Warpspeed

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Re: 48V alternator (ICE driven)
« Reply #74 on: January 22, 2017, 06:51:08 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, 09:55:12 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, 11:55:21 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, 04:34:38 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, 05:55:53 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
A kind word often goes unsaid BUT never goes unheard

electronbaby

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Re: 48V alternator (ICE driven)
« Reply #79 on: February 08, 2017, 11:48:06 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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