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

["Dave Davidson" <davetex99@hotmail.com>]

My TEVan uses SEPEX at 180 volts.  I've never seen any other sepex 
controller at this voltage.  Most are much lower.  I understand arcing can 
be a problem for TEVans.  Chrysler really kept the power down and the van is 
really slow.

I've seen sepex controllers for around 96 volts or so, but don't know 
anything about them.

I believe series DC came about for hobbyists because the industrial EVs have 
historically been series DC.  It was a simple matter to adapt to a car and 
then they started increasing the voltage and power.  A series DC system can 
be made very simple and relatively inexpensive.

I believe the reason high voltage AC systems were chosen was because the 
engineers were familiar with industrial drives, which are at least 208 volts 
three phase.  It was probably not difficult to adapt an industrial drive to 
a vehicle.  I haven't seen any cheap industrial drives on the surplus 
market, though.  It would be fun to experiment.

If you designed a DC system to have all the whistles and bells that current 
AC systems have, it would likely be just as expensive but without the 
advantages of AC.

By the way, Curtis advertises low voltage AC drives on their website.  They 
look like they're not quite powerful enough for an on-road EV unless real 
light, but a 144 volt version would be quite interesting.

Dave Davidson
Laurel, Maryland
1993 Dodge TEVan


>From: Victor Tikhonov <vtikhono@lsil.com>
>Reply-To: ev@listproc.sjsu.edu
>To: ev@listproc.sjsu.edu
>Subject: Re: what is the max bus voltage, 300V?
>Date: Tue, 30 Jul 2002 14:33:13 -0700
>
>Yes. Actual Lee's post was hi voltage vs low voltage, not AC vs DC.
>But really in reality former means the latter.
>
>Can't do hi voltage DC (sparks, brushes, commutator flying apart).
>Can do low voltage AC though. However, not really done in OEM,
>I think partially because special EV drives are adapted industrial
>stationary drives (well developed), and those are always at industrial
>voltages.
>
>Bottom line, while AC can be done with low voltage, there is no
>advantage to do it, more powerful silicon needed, etc. (was
>discussed already). So, naturally, we have what we have.
>
>Victor
>
>David Dymaxion wrote:
> >
> > I find this a very interesting question, and think you bring up a
> > good point, Victor. My guess is it is ultimately economic reasons,
> > believe it or not!
> >
> > Car without regen burns up brakes down a hill = big lawsuit.
> > Solution: AC.
> >
> > DC system is easy to modify, customers start adding things like
> > bypass contactors, raising the voltage. Could lead to an expensive
> > lawsuit. AC is much harder to tinker with.
> >
> > DC has full on failure modes. Remember all the grief Audi got over
> > the sudden aceleration thing? It is harder (though not entirely
> > impossible) for AC to fail full on.
> >
> > Foreseeably silicon will be cheaper than the copper and iron motor,
> > so eventually it could be cheaper to put more into the controller,
> > and use a cheaper common AC motor.
> >
> > Gearboxes are only cheaper for converters because it is already there
> > -- try pricing a new transmission for fun sometimes! Wide AC
> > powerband helps save on tranny cost when designing from scratch.
> >
> > Advertising: Do you want to say you are using 100 year old technology
> > or the latest and greatest?
> >
> > What has surprised me is sepex hasn't been more popular, it seems
> > like a good compromise between AC and DC.
> >
> > --- Victor Tikhonov <vtikhono@lsil.com> wrote:
> > > Lee Hart wrote:
> > > >
> > > > Victor Tikhonov wrote:
> > > > > There are practical advantage of working with smaller wire...
> > > >
> > > > Yes, this is certainly true. There are many little reasons for
> > > picking
> > > > high voltage or low voltage. But the key point is that there is
> > > no
> > > > fundamental reason why one is better than the other.
> > >
> > > Lee, if that would be so, OEM would built 50% low voltage cars (DC)
> > > vehicles and 50% hi voltage (AC) ones. This is not the case
> > > however.
> > >
> > > Granted, in your "fundamental reasons" you don't include non
> > > technical
> > > issues like prices, liability if system fails, serviceability, etc.
> > >
> > > Still, it's like >80% hi voltage OEM systems and <20% low voltage.
> > > For buses it's like 100% to none. You won't find decent 120VDC bus
> > > anywhere.
> > >
> > > I'm not steering opinion, just observing the trends.
> > >
> > > Victor
> > >
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Yahoo! Health - Feel better, live better
> > http://health.yahoo.com




_________________________________________________________________
Send and receive Hotmail on your mobile device: http://mobile.msn.com