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

[Victor Tikhonov <vtikhono@lsil.com>]

Lee Hart wrote:
> 
> Dave Davidson wrote:
..
> > 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.
> 
> Agreed (see, I *can* say it, Victor :-)

Not for long...
 
> > 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.
> 
> Again I agree. This is a good description of what I meant by
> "fashionable" designs; picking a design based what is already available
> and what everyone else is doing.

You're almost agreed on everything...
 
> > 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.
> 
> I don't think this is true.

Oh, no, you disagreed..:-)

 Most of the cost in a motor controller is in
> the power semiconductors and cooling. AC drives have a lot more silicon,
> and so are a lot more expensive. The control electronics cost very
> littl, and with microcomputers, you can have a very large feature set at
> low cost.

Actually as far as I know, is it not the case at least with Siemens.

In AC you typically have 3 or 6 times of power silicon, so instead of
$200 for
DC system you pay $600 or $1,200 for silicon.

But you pay $15,000 for man-hours of software developing and testing,
and another $10,000 tucked in for future engineering support (OEM case).
So DC system with the same feature set will cost almost the same
as AC one, since all the features are in software, not control logic
hardware. So - $25,200 for DC system and $26,200 for most expensive
AC one.

Thus power silicon becomes small fraction of overall final controller 
(inverter) cost to the final customer.