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

[Lee Hart <leeahart@earthlink.net>]

Victor Tikhonov wrote:
> I must compliment Lee. For each statement he always finds counter-
> arguments (which is natural - everything has flip side). I just think,
> imagine if someone would make a series of statements (verbatim as Lee
> just did) first. Lee would find counter arguments to each of such
> "his own statements" in no time, should they come first from
> someone else.

Ah Victor, you have discovered my secret :-)

I do indeed tend to take the opposite side of any argument. I believe it
is important for people to think, and to understand WHY they believe
what they do. Too often, we take things on faith; we believe "X" is true
without questioning why.

One of the neat things about EVs is that they break so many rules. Just
about every rule of thumb that applies to normal ICE cars needs to be
re-thought for EVs. You can't just quote some authority figure -- there
ARE no authorities! You can't just do things the way someone else did it
-- they probably didn't know what they were doing, either!

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.

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.

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. I know a lot about DC drives.
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.

> 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)".

(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