2 phase to 3 phase for motors

[Bob Masta]

I recently saw a small machine shop that
ran 3-phase machines from a homebrew
converter. According to the owner-builder,
he used a big 3-phase motor as a sort of
"flywheel". This motor ran off the incoming
2-phase (standard 220V from utility company)
through some banks of capacitors to the
flywheel motor. Somehow, once it was up
and running, this setup was able to supply
3-phase to the actual working motors in the rest of the
shop. Anyone heard of this before, or have
any links to Web pages?

Thanks!


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

 

[John Popelish]

Bob Masta wrote:

I recently saw a small machine shop that
ran 3-phase machines from a homebrew
converter. According to the owner-builder,
he used a big 3-phase motor as a sort of
"flywheel". This motor ran off the incoming
2-phase (standard 220V from utility company)
through some banks of capacitors to the
flywheel motor. Somehow, once it was up
and running, this setup was able to supply
3-phase to the actual working motors in the rest of the
shop. Anyone heard of this before, or have
any links to Web pages?

You have described it fairly well.
They look like this:
http://www.phaseconverter.com/

The motor is run like a standard (2 phase) capacitor run motor, and
the magnetized rotor shifts the phase a bit to generate 3 phase power
as it rotates.

--
John Popelish

 

[Eric R Snow]

On Thu, 04 Dec 2003 14:03:38 GMT, StopSpam@EveryChance.org (Bob Masta)
wrote:

I recently saw a small machine shop that
ran 3-phase machines from a homebrew
converter. According to the owner-builder,
he used a big 3-phase motor as a sort of
"flywheel". This motor ran off the incoming
2-phase (standard 220V from utility company)
through some banks of capacitors to the
flywheel motor. Somehow, once it was up
and running, this setup was able to supply
3-phase to the actual working motors in the rest of the
shop. Anyone heard of this before, or have
any links to Web pages?

Thanks!


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Greetings Bob,

If you do a google search for rotary phase converter you will find all
the info you need to build your own. Or do a deja news of the
rec.crafts.metalworking newsgroup. And, look at metalworking.com. In
the dropbox are pictures and descriptions of home made rotary phase
converters. I'm not an expert by any means on these things but I
understand a little bit about how they work. After the three phase
idler motor is started on single phase it generates the third phase
which is used to power all the three phase equipment. You can use
capacitors to shift the phase to start the idler motor, or use a
single phase motor to spin it up and then apply the single phase or
even wrap a rope around the shaft, spin it up, and then apply single
phase power to it. Once spinning it will generate the third phase
because all motors, when running, are also generators. Capacitors are
used on the output phases of the idler motor to balance the voltages
under actual running conditions. The capacitors change the phase angle
so the voltage and current are in phase with each other.
ERS

 

[als]

Not long ago, I built one for a friend that seems to be
working out well (10 HP rotary). There are some pictures:
http://people.txucom.net/andysm/pages/3phase02.html
I did some extensive testing on phase relationships
while I was learning, and this was the simplest version
that seemed to work well. I did not publish the results
of the tests of various other designs (other rotaries
and statics), and of the various components tested (some
to destruction), but I can.
<als> alsAThal-pcDOTorg (don't bother to reply to the spam address).




In article <3fcf3d10.4178571@news.itd.umich.edu>, StopSpam@EveryChance.org says...

I recently saw a small machine shop that
ran 3-phase machines from a homebrew
converter. According to the owner-builder,
he used a big 3-phase motor as a sort of
"flywheel". This motor ran off the incoming
2-phase (standard 220V from utility company)
through some banks of capacitors to the
flywheel motor. Somehow, once it was up
and running, this setup was able to supply
3-phase to the actual working motors in the rest of the
shop. Anyone heard of this before, or have
any links to Web pages?

Thanks!


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

 

[John Popelish]

als wrote:

Not long ago, I built one for a friend that seems to be
working out well (10 HP rotary). There are some pictures:
http://people.txucom.net/andysm/pages/3phase02.html
I did some extensive testing on phase relationships
while I was learning, and this was the simplest version
that seemed to work well. I did not publish the results
of the tests of various other designs (other rotaries
and statics), and of the various components tested (some
to destruction), but I can.

Very neat. But I have two small concerns. At the moment you hit the
start, there is an unknown voltage on the pair of 250 uf caps and a
possibly quite different unknown voltage on the bank of 4 running caps
that get connected directly in parallel with a contact. I think I
would have added a small inductance or resistance in series with the
start caps to limit that equalization current, and also a bleed
resistor across the start cap bank.

--
John Popelish

 

[Kim Clay]

On Fri, 12 Dec 2003 23:59:02 GMT, John Popelish <jpopelish@rica.net>
wrote:

als wrote:

Not long ago, I built one for a friend that seems to be
working out well (10 HP rotary). There are some pictures:
http://people.txucom.net/andysm/pages/3phase02.html
I did some extensive testing on phase relationships
while I was learning, and this was the simplest version
that seemed to work well. I did not publish the results
of the tests of various other designs (other rotaries
and statics), and of the various components tested (some
to destruction), but I can.

Very neat. But I have two small concerns. At the moment you hit the
start, there is an unknown voltage on the pair of 250 uf caps and a
possibly quite different unknown voltage on the bank of 4 running caps
that get connected directly in parallel with a contact. I think I
would have added a small inductance or resistance in series with the
start caps to limit that equalization current, and also a bleed
resistor across the start cap bank.

Hmmm... How does it start? Shouldn't K1 be powered from the main breaker
instead of its own contacts (using the 0.5A fuse)?

If the idler (or a load motor) is not spinning there will be no voltage
across the pair of 250V start caps (discharged through the deactivated
start relay), or the run caps. Both are discharged through the idler
windings.

A bleed resistor across the start caps is always a nice feature just in
case the start relay contacts go open.

rec.crafts.metalworking is where they do lots of this.

Check out http://www.metalwebnews.com/msc.html (at the top) for
starters.

Also, by the two 24V transformers, there seems to be an option to use
the !safety ground! rather than the neutral as return for the control
transformers?

Nice looking install!

 

[als]

I apologize for the errors in the schematic. Drew it from memory,
which seems to be failing more often lately.
I will correct it, and also add some more drawings of some other
converters (static and rotary) as soon as I get a round tuit.
Explanatory defense follows

In article <8sbltv8o2r45gmgopugfmgtlign7lm060r@4ax.com>, kimclay@myrealbox.com says...

On Fri, 12 Dec 2003 23:59:02 GMT, John Popelish <jpopelish@rica.net
wrote:

als wrote:

Not long ago, I built one for a friend that seems to be
working out well (10 HP rotary). There are some pictures:
http://people.txucom.net/andysm/pages/3phase02.html
I did some extensive testing on phase relationships
while I was learning, and this was the simplest version
that seemed to work well. I did not publish the results
of the tests of various other designs (other rotaries
and statics), and of the various components tested (some
to destruction), but I can.

Very neat. But I have two small concerns. At the moment you hit the
start, there is an unknown voltage on the pair of 250 uf caps and a
possibly quite different unknown voltage on the bank of 4 running caps
that get connected directly in parallel with a contact. I think I
would have added a small inductance or resistance in series with the
start caps to limit that equalization current, and also a bleed
resistor across the start cap bank.

There is a 33k, 2W resistor across the start caps (not shown in the
drawing). It is actually not necessary, since the potential relay
recloses when the converter is shut down, which discharges the start
caps into the idler. I had added it so I would not be startled when
wiring/testing.

Hmmm... How does it start? Shouldn't K1 be powered from the main breaker
instead of its own contacts (using the 0.5A fuse)?

You are correct. The fuse IS connected to one of the LINE IN terminals.
My error in the drawing. Sorry.

If the idler (or a load motor) is not spinning there will be no voltage
across the pair of 250V start caps (discharged through the deactivated
start relay), or the run caps. Both are discharged through the idler
windings.

A bleed resistor across the start caps is always a nice feature just in
case the start relay contacts go open.

rec.crafts.metalworking is where they do lots of this.

Check out http://www.metalwebnews.com/msc.html (at the top) for
starters.

Also, by the two 24V transformers, there seems to be an option to use
the !safety ground! rather than the neutral as return for the control
transformers?

The option to use safety ground is there since the converter is mounted
in close proximity to the main panel. I incorporated it in order to
use the ground as a reference to insure that the shop ground was in order.
The original design used 3 transformers (one on each leg), and a couple
more relays, but it started to get complicated (!).
I made a decision to use only parts that were readily available, and
to make it simple enough that any decent electrician could understand
and repair it if necessary.

Nice looking install!

Thanks. It would have looked nicer, but in went thru several iterations,

since I was mainly building it out of parts on hand. Woulda' done it a
little different if 1) the parts had to be purchased, and 2) the application
or environment was different.

<als>