Re: what is the max bus voltage, 300V?

[Victor Tikhonov <vtikhono@lsil.com>]

Lee Hart wrote:
> 
> Therefore it is important that we see things as they are. Study the
> facts, not opinions. Do experiments, not surveys. Go by the data, not
> opinions.

You're right again. The problem for many is cost of [failed] experiments
and time it takes to do it.

Take ADC motors. Why a newbie in the field is most likely to use it?
Because everyone else around him, no matter whom he asks, is most
likely to use it too. So in a short while he gets impression that this
is *the* best choice, otherwise so many people wouldn't successfully
use it. Why invent a wheel and try if ADC is proven and works?

ADC historically was about all that was available for long time
(aside Kostov and GE). Over the years it filled EV market with
these motors, making impression that *therefore* it is best solution,
or why else 90% of EVs are using it?

With limited budget I was not going not to trust anybody and to 
experiment to see if ADC indeed is better than, say GE motors

(I'd had to buy/borrow both, set up measurement gear, get rid of
unwanted motor later,...) I was itching to be on the road ASAP
optimal motor or not. You know that feeling...

If you're new, it's natural to turn to "experts" who are done it.
People are no experts, they just in turn looked at someone else,
it's a snow ball effect.
 
> All too often in our society, somebody gives you an answer (their
> answer) to a problem, and then "supports" it with selective facts. They
> exaggerate things that support it, and leave out things that do not. We
> get what sounds like a convincing case, even though it is all hogwash.

Yes, I can see it everyday. Everybody knows it's much better to be
honest,
yet hogwash or plain lying is everywhere. I'm afraid it's considered
successful business if it makes money by lying to customers -only
bottom line matters...

OK, sorry, back to EV
 
> One test for this is to assume the opposite is true, and try to prove it
> the same way. If it sounds just as convincing, then you have proven
> nothing; both positions are unsupportable.
> 
> So... Victor knows a lot about AC drives.

No, I'm learning as I go too.

> I know a lot about DC drives.

Agreed :-)

> Each of us debates on one side of the issue. Neither of us can get away
> with phony facts or opinions, because the other will call him on it. One
> by one, the legitimate facts pile up on each side of the issue.
> 
> In the end, there will of course be a large body of information on both
> AC and DC. Anyone who reads thru it will learn that neither is always
> the right choice. Depending on how you weight the facts, either might be
> the best choice for your situation.

Have you tried to work as a judge? You'd learn instant respect!
 
> > Often each paragraph starts from "But...". I've never seen a single
> > post from anyone on the list for as long as I subscribe, to which
> > Lee would say "Agreed", "Agreed", ... after each paragraph :-)
> 
> Agreed. :-)
> 
> If one goes thru my old posts, you can easily find me arguing with
> myself. I'll take one side of an issue one time, and the other side
> another time. All it takes to set me off is to say something like, "Of
> course, everybody knows that X is the only way to do it)".

That's why we all like you Lee
 
> (PS -- If you get tired of supporting AC and want to try DC, we can
> switch sides. I can argue just as convincingly on the other side of the
> issue :-)
> 
> >>> AC has certain attributes which lend themselves to a wide power band.
> 
> >> For example?
> 
> > Linear torque from zero to about half of max RPM.
> 
> > Lee, I think I know your response: "But, you can make controller
> > do the same to a DC motor! it's not the property of the motor itself"
> > Sure. Just for some reason no one does it. And it's desirable.
> 
> Agreed; you're right. Constant torque means the controller is delivering
> constant current. That's exactly what we get with series motors and PWM
> controllers in current limit.
> 
> But what usually happens is that we have a pack voltage that is so low
> that the series motor comes out of current limit at a relatively low
> rpm. To see an example of a DC car that behaves like an AC car, ask Paul
> Compton about Clare Bell's Porsche 914. I believe they were running an
> Advanced DC 9" motor (rated 144v) with a 288v pack. The controller ran
> in current limit up to a very high rpm. The car performed extremely
> well, and there was no problem with arcing despite the high voltage.
> --
> Lee A. Hart                Ring the bells that still can ring
> 814 8th Ave. N.            Forget your perfect offering
> Sartell, MN 56377 USA      There is a crack in everything
> leeahart_at_earthlink.net  That's how the light gets in - Leonard Cohen

I won't get tired supporting AC. When I entered into EV field in 1994,
all I had is dream about EV, and inspiration by ACP. As you know my
first conversion was with 8" DC, although I knew it's not the best
choice. I wouldn't argue with someone that ADC is best choice because
I used it. It was all that was available/affordable to me.

You wouldn't stand behind the statement that aircraft generators are
best choice, therefore you used one in your first conversion, wouldn't
you?
You used it because you had it and could make it do the job.

So I'm not pro AC because I have it, it's the other way around. I was
pro AC 
when I didn't have it too. And, as you said, I'm not saying AC is better
for every situation. All I'm saying - AC systems specifically 
optimized for EV use by large resourceful OEM with extensive R&D,
exist, and in my case I was able to put my hands on it (and you can
too).
You can't beat that.

BUT, for all practical purposes in each case the best is what one have 
in his hands (or can get easily/cheaply) NOW, no matter what 
everyone says. Like your aircraft starter-generators were for you
a while ago.

Victor