[Oeva-list] DC to 3 phase AC inverter/controller

Nev Okyay nevokyay at yahoo.com
Mon Oct 20 13:22:06 PDT 2008


I have spent fair amount of time googling to
find a DC to 3 phase inverter/controller.  I 
wanted to share the following info with the
group hoping that it will be useful to somebody.

These units are called interchangably 'inverters'
, 'motor controllers', VFDs 'variable frequency
drives', or simply 'drives'.

If you search for inverters you will find either
very low power ones that work off of the cigarette
lighters, or huge ones designed for solar panels
starting from $17K and up.

But as Rick Barnes have keenly observed and pointed
out to me earlier, some inverters will work with 
DC input if you derate them. :)

I started looking into Hitachi drives.  Normally
these drives work with 2 phase or 3 phase input
power, however unadvertised feature of these drives
is that they can be wired to work with DC input
without derating them operating close to %95
efficiency.  I haven't seen anybody using Hitachi
drives in the evalbum projects.

L200P series drives operate up to 10HP motors, 
L300P series drives operate 15HP and above.  
There are many models in each category but all
can be divided into low voltage ones (200V input
voltage) and high voltage ones (400V input).

AC motors have the following features:
1. Very low cost and easy availability. (please
see my previous message).
2. You can spin the motor forward or backward.
3. Dynamic breaking.
4. Regenerative power.
5. Not a big deal, but no need to worry about
replacing brushes.

Of course the biggest disadvantage for 3 phase
AC motors is that the drive for them is very
expensive.  For example, for 15HP motor (11KW)
the brand new Hitachi drive was $925 from ebay.
10HP Hitachi drive little over $600.

But these drives are like computers, always new
models coming out that are smaller, lighter, with
more features, and cheaper.  The case in point is
X200 series of drives that are equal to L200P series,
but they have more features and are cheaper.  10HP
version is little over $550 from ebay brand new.

As a reference, here is a document showing 
different connection options for DC input.
Hitachi Application Note: Powering inverters
from a DC supply.

http://support.automationdirect.com/docs/hitachi_dcpower.pdf

User guide for L300P.  L300P series inverter
instruction manual.

http://www.driveswarehouse.com/documentation/Hitachi/L300PM.pdf

Although I don't have the batteries yet, I can
confirm that the Hitachi unit L300P low voltage
version works fine with DC input.  I used a xformer
to convert 110V to 220V AC and used a bridge diode
rectifier and a capacitor to convert that to DC
(~ 320V).  Hitachi low voltage units work with
any DC input from 200V +/- 10% upto 400V +/- 10V

- nev


--- Rick Barnes <barnes.rick at verizon.net> wrote:

> Cool!
> 
> I recommend deep cycle batteries (golf cart
> batteries). You will not get
> very good life from the marine batteries.
> 
> Rick
> 
--- deleted ----


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