3 phase inverter using Stamp2

Archiver

I would like to make a 3 phase inverter for varaible speed control of
small 3 phase motors using one of the Stamps. The 3 phase sine wave
generation process is well documented on various web sites, and
requires an fast accurate variable timebase and lookup table to drive
the IGBT's. It does not seem to be easily achieved using a Stamp2.
Has anyone any experience or links on this topic ?

Archiver

> I would like to make a 3 phase inverter for variable speed control of
> small 3 phase motors using one of the Stamps. The 3 phase sine wave
> generation process is well documented on various web sites, and
> requires an fast accurate variable timebase and lookup table to drive
> the IGBT's. It does not seem to be easily achieved using a Stamp2.
> Has anyone any experience or links on this topic ?

Hi There:

For what they cost nowadays, you may as well just buy a drive from someone
like automationdirect.com and then do the control interface to the outside
world with the stamp. If you also configure the circuit properly, you can
make the variable speed drive work as a phase converter to make three phase
from single phase power.

The other approach is to take existing ASIC's that can generate the PWM
algorithm plus provide the interlocking between the inverter IGBT's and link
them to some other ASIC's so that you can just use the stamp for things like
external control interfacing. There is a great deal of satisfaction in
rolling your own drive but it can be very time consuming.

A small cautionary note about IGBT's that I have seen on all the variable
speed drives I have ever serviced: They require not only isolator chips but
the transistors that fire the positive voltage rail to the three phase
output need INDIVIDUAL supplies. This means you need a power supply supply
system that has four isolated supplies to drive the IGBT's (unless someone
like International Recitifier has come up with a firing interface IC that
does this) plus another isolated power supply section for the logic
controls. This can be quite a challenge. Also IGBT's are very static
sensitive and each supply must provide +15VDC/-15VDC to make them work
properly. If the drive is small enough you could substitute power MOSFET's
but the requirements for isolated supplies are still needed.

Hopefully this sheds some light on the subject. Let me know if you need any
further information.

Regards,

Gerry Shand
res@i...

Archiver

In a message dated 7/17/2004 9:08:02 AM Eastern Daylight Time,
res@i... writes:

If you also configure the circuit properly, you can
make the variable speed drive work as a phase converter to make three phase
from single phase power.



Actually, all you need to do for this is to purchase a single phase input
inverter with a 3 phase output. Many of the European machine manufactureres do
this as a normal OEM item. They are less expensive and even if you only
have 3 phase power going to that machine, all you have to do is use 2 of the 3
three phase lines for single phase power.

I also agree, you don't want to try and re-invent the wheel on this. You
will be working with "line" voltages which could be as high a 600 or more Vac
and are lethal. Even in a residential evironment it would probably be 220 Vac
and that too can be lethal. The manufacturers of these units put a lot of
safety features into them to protect not only the equipment but people as well.

Good luck,

P.S. If all you want to do is control the speed, a plain old potentiometer
works great with these units. Of course, it isn't quite as glamorous as
using a Stamp and probably not nearly the fun.



Randy Abernathy
4626 Old Stilesboro Road NW
Acworth, GA 30101-4066
Phone / Fax: 770-974-5295
Mobile: 678-772-4113
E-mail: cnc002@a...

I furnish technical support, repair, and other related services for your
industrial woodworking machinery. My background as Senior Service Engineer for
the SCMI Group for nearly fifteen years with factory training, combines with
my extensive background in electronics, mechanics, pneumatics, electrical and
CNC machinery to offer you needed support for your machinery.


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