19 Oct
2007
19 Oct
'07
3:22 a.m.
From a UK point of view 'motor' as in motor-generator would be
taken to
some form of internal combustion engine.
I have heard lots of references to 'motor-generators' but never an
'engine-generator'.
Devices used for AC to DC, DC to AC and voltage conversion using a
electric motor coupled to a generator would be referred to as 'rotary
convertors'.
No, when I've talked to people (in the UK) about a rotary converter,
they were talking about a large 3 phase motor wired up with big
capacitors so that it could be started on a single phase supply and
once turning, the other two windings would provide the other two
phases whilst the pulses to the first winding would keep it running
at the right speed. Of course for a 10kVA supply, I would have needed
at least a 30kVA motor as only one phase was actually driving it.
It may be
European vs US usage, but in the US "motor" almost always
means electric motor in this and other contexts. So what you
That tends to be UK usage too. The thing under the bonnet (OK,
hood) of
a car is called an 'engine' over here. 'Motor' for that would be very
uncommon.
To me, a 'motor generator' is just that. An electric motor driving an
electric generator, to be used to convert voltage/frequency, etc. A
'rotary converter' (or 'Dynamotor; if oyu go back far enough) is a
simialr thing with common field windings/frame/etc rather than 2
separate electrical machines with the shafts coupled.
Yes, but generator also means a machine converting a turning motion
into DC. Cars prior to the mid sixties had generators, after that
they have alternators with a bridge rectifier.
call a "motor-generator" would be here
just plain called a
"generator"
A 'generator' over here is either just the mechanical-to-electircal
energy converter or , as you said, a heat engine coupled to such a
machine. Certainly if you hired a 'generator' (as somebody
suggested we
should do for a VCF-type event), you'd expect to get something with
the
engine included. I don't know how common these other term are
across the Pond, but an
'alternator' is an AC-output geneterator, a 'Dynamo' (short for
'Dynamo-electric machine' is a generator, normally DC output, with a
wound field, and a 'Magneto' (short for 'Magneto-electric machine'
is a
genatore with a permanent magnet field. Which means the common bicycle
dynamo (as it's normally called over here' is in fact a magneto....
I agree with all but the last part. A magneto is a coil mounted next
to a flywheel, the flywheel having a permanent magnet attached which
when it moves past the coil, generates an electrical spike which
drives the spark plug at exactly the right point in the engine cycle
for a two stroke engine, or for a four stroke, one spark is just
wasted, though it would be possible for the magneto to be run off the
camshaft. The Magento was in turn was a big advance on the old hot
tube ignition, but thats another story.
Roger Holmes
ICT 1301
UK101
Apple 2,3,Lisa and Macs
19 Oct
19 Oct
9:18 a.m.
On 19 Oct 2007 at 11:22, Roger Holmes wrote:
No, when I've talked to people (in the UK) about a
rotary converter,
they were talking about a large 3 phase motor wired up with big
capacitors so that it could be started on a single phase supply and
once turning, the other two windings would provide the other two
phases whilst the pulses to the first winding would keep it running
at the right speed. Of course for a 10kVA supply, I would have needed
at least a 30kVA motor as only one phase was actually driving it.
There is the class of the commutating synchronous rectifier (for want
of a better made-up term). See
http://www.nycsubway.org/tech/power/rotary.html
To be honest, I suspect that a gizmo of this vintage is simply too
much of an antique to have been used to power any mainframe systems.
The term for the ildling 3-phase motor driven from a single-phase
source via one or more large capacitors used here in the US is
usually "Phase Converter" or "Rotary phase converter" or "Dynamic
phase converter" to differentiate itself from a simple capacitor bank
feeding a 3-phase motor, sometimes called a "static phase converter".
There is a trade name for the former, Rotocon, and occasionally
you'll see their reference to their products as "rotary converters",
but that's not general usage.
Regardless, I don't know if I'd try powering a three-phase computer
power supply from one.
Cheers,
Chuck
10:33 a.m.
Regardless, I don't know if I'd try powering a
three-phase computer
power supply from one.
With older gear, why not? Most of that classic mainframe stuff has
brute force power supplies, often fed by voltage regulating
transformers (almost always a Sola, it seems).
The three phase motors in the drives will just help things along, as well.
--
Will
10:47 a.m.
On 19 Oct 2007 at 13:33, William Donzelli wrote:
With older gear, why not? Most of that classic
mainframe stuff has
brute force power supplies, often fed by voltage regulating
transformers (almost always a Sola, it seems).
The three phase motors in the drives will just help things along, as well.
My experience with these things (admittedly only with machine tools)
shows a strong tendency for less-than-perfect (i.e. 120 degree) phase-
to-phase relationships and fairly drastic phase-to-phase voltage and
current variations. They work with motors, but none allows for full
motor nameplate loading (usually around 80 percent of nameplate). My
take is that they work "sort of". Heaven only knows how a power
supply would behave attached to one of these things.
My feeling is that if you have to power some three-phase big iron
from a single-phase source, it's probably better to
take a look at
one of the modern (and expensive) solid-state converters--or get
some
real three-phase distribution installed.
Cheers,
Chuck
11:55 a.m.
On Friday 19 October 2007, Chuck Guzis wrote:
On 19 Oct 2007 at 13:33, William Donzelli wrote:
Or, of course, you could just find a big heavy single phase motor, and
pair it up with a 3phase motor of the same RPM rating with a
shaft-coupler, and make your own single-to-three phase MG set.
Pat
--
Purdue University Research Computing --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
With older gear, why not? Most of that classic
mainframe stuff has
brute force power supplies, often fed by voltage regulating
transformers (almost always a Sola, it seems).
The three phase motors in the drives will just help things along,
as well.
My experience with these things (admittedly only with machine tools)
shows a strong tendency for less-than-perfect (i.e. 120 degree)
phase- to-phase relationships and fairly drastic phase-to-phase
voltage and current variations. They work with motors, but none
allows for full motor nameplate loading (usually around 80 percent of
nameplate). My take is that they work "sort of". Heaven only knows
how a power supply would behave attached to one of these things.
My feeling is that if you have to power some three-phase big iron
from a single-phase source, it's probably better to take a look at
one of the modern (and expensive) solid-state converters--or get some
real three-phase distribution installed. 
12:09 p.m.
New subject: VAXen at home - 3ph source/MG set?
On Fri, 19 Oct 2007, Patrick Finnegan wrote:
You know, it's ironic this topic has come up, as I'm currently working on
converting my 3ph SGI Onyx to single phase and had looked into static and
rotary phase convertors. Having never had any reason to look at one before
I started anew - and decided quickly that they did not appear to be safe
for computer use.
Where I am the cost of installing three phase would likely be in the
quadruple digits (Ah, electricians, well paid princes of the earth).
Thankfully the conversion on the SGI is relatively trivial with the
appropriate bits and pieces, nevertheless I was wondering about the
chances of building an MG set to produce a stable three-phase source.
On the off chance I end up dealing with this problem again, and won't be
in a position to do a conversion, does anyone know about the math involved
to work out what kind of sizes of motors would be required to produce such
a contraption?
Thanks all;
JP Hindin
My feeling is
that if you have to power some three-phase big iron
from a single-phase source, it's probably better to take a look at
one of the modern (and expensive) solid-state converters--or get some
real three-phase distribution installed.
Or, of course, you could just find a big heavy single phase motor, and
pair it up with a 3phase motor of the same RPM rating with a
shaft-coupler, and make your own single-to-three phase MG set.
12:28 p.m.
New subject: VAXen at home - 3ph source/MG set?
On Friday 19 October 2007, JP Hindin wrote:
You know, it's ironic this topic has come up, as
I'm currently
working on converting my 3ph SGI Onyx to single phase and had looked
into static and rotary phase convertors. Having never had any reason
to look at one before I started anew - and decided quickly that they
did not appear to be safe for computer use.
The easiest and best way to do this, is to either rewire things to be
happy with single-phase, or just run single phase to it.
In general most modern-ish computer three phase supplies (since at
least '90 or so) will be perfectly happy if you wire them up to a
single phase supply - you may want to bond the third phase to one of
the "hot" wires of the single phase supply.
I've run IBM S/390 and SP systems off of a single phase supply like
this, with no other work to convert them, and they're perfectly happy
with it. One small "gotcha" is that it may have some control bits of
the power supply that are wired to two of the three phases, so if you
have the third phase bonded to one of the hot leads, and it doesn't
work, you may want to try bonding it to the other phase instead.
Worrying about any sort of single to three phase converter for a
modernish computer is just a waste of money. The only things that
truly need three phase (real or improvised) are things with three-phase
motors in them...
Pat
--
Purdue University Research Computing --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
12:37 p.m.
New subject: VAXen at home - 3ph source/MG set?
Patrick Finnegan wrote:
Worrying about any sort of single to three phase
converter for a
modernish computer is just a waste of money. The only things that
truly need three phase (real or improvised) are things with three-phase
motors in them...
If I'm remembering correctly, this includes my ES/9021.
Peace... Sridhar
1:05 p.m.
New subject: VAXen at home - 3ph source/MG set?
Patrick Finnegan wrote:
Worrying about any sort of single to three phase converter for a
modernish computer is just a waste of money. The only things that
truly need three phase (real or improvised) are things with three-phase
motors in them...
Unless it has a Ferroresonant transformer...then you *need* 3-phase.
The other thing to note is that 3-phase was used to keep the wiring
"reasonable". Wiring up a 3-phase 24A circuit (and cabling) is much
easier than a single phase 75A circuit (although I've run a 3-phase 75A
branch in my shop...100' of #3 wire (4 conductors) is *not* fun).
--
TTFN - Guy
1:23 p.m.
New subject: VAXen at home - 3ph source/MG set?
On Friday 19 October 2007, Guy Sotomayor wrote:
Patrick Finnegan wrote:
What "modernish" (I think I said since about '90) uses a ferro-resonant
transformer?
Worrying about any sort of single to three phase
converter for a
modernish computer is just a waste of money. The only things that
truly need three phase (real or improvised) are things with
three-phase motors in them...
Unless it has a Ferroresonant transformer...then you *need* 3-phase. The other thing to note is that 3-phase was used to
keep the wiring
"reasonable". Wiring up a 3-phase 24A circuit (and cabling) is much
easier than a single phase 75A circuit (although I've run a 3-phase
75A branch in my shop...100' of #3 wire (4 conductors) is *not* fun).
You could also just parallel three 10AWG wires for each phase. (Or, two
6AWG)
Pat
--
Purdue University Research Computing --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
21 Oct
21 Oct
11:13 a.m.
New subject: VAXen at home - 3ph source/MG set?
On Friday 19 October 2007 19:27, William Donzelli wrote:
Yeah, fine, I did look it up in my Code book, and you're not supposed to
parallel lines less than 0 AWG in size. This isn't something I'd do
myself, anyhow, as 3 AWG conductors aren't *too* bad to run as long as
you keep the number of bends down to a minimum.
Pat
--
Purdue University ITAP/RCAC --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
You could also
just parallel three 10AWG wires for each phase. (Or,
two 6AWG)
Some electricians might have something to say about that.
19 Oct
19 Oct
4:30 p.m.
New subject: VAXen at home - 3ph source/MG set?
Unless it has a Ferroresonant transformer...then you
*need* 3-phase.
Some three phase transformers can be run off one phase - it depends
how they are wound. Some of the guys that run old tube broadcast
transmitters have done this, and there is a good article on it in an
old issue (ten years ago?) of Electric Radio magazine.
--
Will
5:04 p.m.
New subject: VAXen at home - 3ph source/MG set?
William Donzelli wrote:
Except that after going through a 3-phase bridge rectifier, you have
360Hz (with a good DC component) vs 120Hz that drops to 0v so you need a
lot less filter caps with the 3-phase. And frankly the situation I'm
dealing with draws ~500A @12V - that's a butt load of current over
single phase (and that's just the stuff that *requires*
3-phase...there's a bunch more power that splits the phases to get
standard 120v single phase). Total load requirements are 70A across all
3-phases (210A single phase...how the *hell* are you going to wire that?).
--
TTFN - Guy
Unless it has
a Ferroresonant transformer...then you *need* 3-phase.
Some three phase transformers can be run off one phase - it depends
how they are wound. Some of the guys that run old tube broadcast
transmitters have done this, and there is a good article on it in an
old issue (ten years ago?) of Electric Radio magazine.
5:30 p.m.
New subject: VAXen at home - 3ph source/MG set?
Except that after going through a 3-phase bridge
rectifier, you have
360Hz (with a good DC component) vs 120Hz that drops to 0v so you need a
lot less filter caps with the 3-phase. And frankly the situation I'm
dealing with draws ~500A @12V - that's a butt load of current over
single phase (and that's just the stuff that *requires*
3-phase...there's a bunch more power that splits the phases to get
standard 120v single phase). Total load requirements are 70A across all
3-phases (210A single phase...how the *hell* are you going to wire that?).
If it is a KL10, you will not need to worry about this at all, because
the power supplies will fail anyway.
But seriously...
If you are dealing with something as big as a KL10, I think having
real 3 phase is basically required. I would not even try it with a
converter - god only knows how many HP the motor would need to be.
Does your building not have 3 phase service available?
If you were dealing with something like VAX-11/780 sized, with much
lower current requirements, you probably could sling a bunch of extra
caps on the side and have everything happy. Big ass 20 volt
electrolytics are dime a dozen.
--
Will
7:46 p.m.
New subject: VAXen at home - 3ph source/MG set?
William Donzelli wrote:
:-P
Except that
after going through a 3-phase bridge rectifier, you have
360Hz (with a good DC component) vs 120Hz that drops to 0v so you need a
lot less filter caps with the 3-phase. And frankly the situation I'm
dealing with draws ~500A @12V - that's a butt load of current over
single phase (and that's just the stuff that *requires*
3-phase...there's a bunch more power that splits the phases to get
standard 120v single phase). Total load requirements are 70A across all
3-phases (210A single phase...how the *hell* are you going to wire that?).
If it is a KL10, you will not need to worry about this at all, because
the power supplies will fail anyway.
But seriously...
If you are dealing with something as big as a KL10, I think having
real 3 phase is basically required. I would not even try it with a
converter - god only knows how many HP the motor would need to be.
Does your building not have 3 phase service available?
No, I have 125A 3-phase service into my shop...it's barely enough. :-/
If you were dealing with something like VAX-11/780
sized, with much
lower current requirements, you probably could sling a bunch of extra
caps on the side and have everything happy. Big ass 20 volt
electrolytics are dime a dozen.
Na. All of the supplies in the 11/780 are single phase (with std 110v
15A plugs even). The power controller just splits the phases. As I
said before, it simplifies the wiring from the system to the "mains".
My DS570 uses a 3-phase power controller also. Again, it's convenient
but not exactly necessary.
--
TTFN - Guy
7:58 p.m.
New subject: VAXen at home - 3ph source/MG set?
Na. All of the supplies in the 11/780 are single
phase (with std 110v
15A plugs even). The power controller just splits the phases.
I was just using the VAX-11/780 as a size unit (VUS), not as an
explicit example. Sort of "small mainframe-ish".
As I
said before, it simplifies the wiring from the system to the "mains".
ALRIGHT, Alright...you broke the camels back...I have had enough!
In the US, it is not MAINS, it is the LINE. Most US electricians will
know what you mean, but may give you funny looks if you call it
"mains", and not buy you a beer at the end of the day because you
might be un-American.
Non-US list members may still, of course, call it "mains".
--
Will, son of Chicago electrician
10:21 p.m.
New subject: VAXen at home - 3ph source/MG set?
William Donzelli wrote:
OK. I just like using concrete examples.
Really? :-) I have enough of those "fire hoses" going from the
panels
to systems, that I just can't envision using single phase in those
situations. Geez, the KL's power cable is 2+" in diameter (and the
"plug" probably weighs in at 10+#).
Na. All of
the supplies in the 11/780 are single phase (with std 110v
15A plugs even). The power controller just splits the phases.
I was just using the VAX-11/780 as a size unit (VUS), not as an
explicit example. Sort of "small mainframe-ish".
As I
said before, it simplifies the wiring from the system to the "mains".
ALRIGHT, Alright...you broke the camels back...I have had enough!
In the US, it is not MAINS, it is the LINE. Most US
electricians will
know what you mean, but may give you funny looks if you call it
"mains", and not buy you a beer at the end of the day because you
might be un-American.
Sorry, I've always used "line" for "dainty" power
(radios and such) and
"mains" when something heftier is called for. :-) But then again I'm
just a software jock who masquerades as a EE on occasion. :-)
--
TTFN - Guy
10:50 p.m.
New subject: VAXen at home - 3ph source/MG set?
On 19 Oct 2007 at 22:21, Guy Sotomayor wrote:
Sorry, I've always used "line" for
"dainty" power (radios and such) and
"mains" when something heftier is called for. :-) But then again I'm
just a software jock who masquerades as a EE on occasion. :-)
It's a habit from business dealings.
I use the word "mains" when I know there are friends in Blighty
reading the list because I know that most "murricans will know what I
mean. On the other hand, I prefer to use "ground" rather than
"earth" when speaking about a common return, knowing full well that
most of the list members from the UK will know exactly what I mean.
Really, the UK usage "mains" makes a bit more sense--we have water
mains, don't we?
But I don't think I'll *ever* undertand cricket scores... :)
Cheers,
Chuck
21 Oct
21 Oct
11:09 a.m.
New subject: VAXen at home - 3ph source/MG set?
On Friday 19 October 2007 20:04, Guy Sotomayor wrote:
Except that after going through a 3-phase bridge
rectifier, you have
360Hz (with a good DC component) vs 120Hz that drops to 0v so you
need a lot less filter caps with the 3-phase. And frankly the
situation I'm dealing with draws ~500A @12V - that's a butt load of
current over single phase (and that's just the stuff that *requires*
3-phase...there's a bunch more power that splits the phases to get
standard 120v single phase). Total load requirements are 70A across
all 3-phases (210A single phase...how the *hell* are you going to
wire that?).
Ok, well, I was specifically talking about JP's Onyx 2. It has been my
experience with more modern machines (like my IBM SPs and S/390s, and
like JP's Onyx2), that the power supplies are generally over-designed
enough that they won't really care if they're running off single phase
or three phase power. Either they're designed already to run off
either single or three phase (like the Onyx 2 I was referring to, and
the IBM SPs I've got), or they have an already over-designed amount of
power-soothing capacitors (which are going to be designed to work at
over the max possible loading of the computer, which it should
basically never reach, at least after the inital inrush current).
Also, good design dictates that the power supply should be designed to
be able to run for a cycle or two with lower or no input voltage, first
so that you can get a "useful" power fail interrupt, and second, so
that you can ride out short brownout or power blips from inrush
current, say from a disk drive or A/C compressor spinning up. :) I'll
further argue that if the equipment can tolerate a missing cycle of
A/C, then it should have no problem dealing with the difference between
rectified single and three phase power. Of course, not all machines
are designed "well", and some things won't appreciate the difference,
but I'd imagine that the problems will mostly be limited to much older
equipment, with linear, instead of switching, power supplies, and which
is fairly big in size (and might warrant 200A 208V 3ph service or even
480V 3ph service:).
I wasn't exactly trying to say that Big Computers like your PDP-10
should be run off single phase instead of 3-phase power*, it's
possible, but probably doesn't make sense. It probably makes more
sense to just buy a 3ph diesel (or LP/natural gas) generator to run it
if you're not going to do it frequently, than to convert the machine to
3 phase power. Or, just get 3phase power, of course. The cost of
installation will quickly get outweighed by the cost of running the
machine for any significant period of time. :)
* Though, honestly, you aren't 100% correct in your calculation; most
people would use 240V single phase instead of 208V three phase... 240V
1ph delivers 2/3 of the power of a 208V 3ph circuit of the same
amperage... so your 70A 208V feed is equivalent to a ~100A 240V 1ph
feed. I actually do have a 100A 240V "branch circuit" run in
my "computing facility", though it's to run a machine with more
mad-scientist appeal than computer-scientist appeal. :)
Pat
--
Purdue University ITAP/RCAC --- http://www.rcac.purdue.edu/
The Computer Refuge --- http://computer-refuge.org
19 Oct
19 Oct
1:11 p.m.
New subject: VAXen at home - 3ph source/MG set?
Worrying about any sort of single to three phase
converter for a
modernish computer is just a waste of money.
This amounts to declaring anything that depends on three-phase as
non-"modernish". But there really are substantive differences between
three-phase and single-phase for supplying power, since rectified
single-phase drops to zero (even if full-wave rectified). Rectified
three-phase has a substantial minimum DC component (cos(30?), about
.866, times peak, if full-wave rectified; cos(60?), or .5, times peak,
if half-wave rectified - minus rectifier losses - assuming pure
sine-wave input - I think).
This means substantially less need for filter caps and the like -
indeed, if you're willing to depend on having all three phases, and
your regulators are good enough at ripple rejection, you may be able to
run without any filter caps on the unregulated side of the regulator.
Try feeding *that* single phase!
/~\ The ASCII der Mouse
\ / Ribbon Campaign
X Against HTML mouse at rodents.montreal.qc.ca
/ \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
4:34 p.m.
New subject: VAXen at home - 3ph source/MG set?
I've run IBM S/390 and SP systems off of a single
phase supply like
this, with no other work to convert them, and they're perfectly happy
with it. One small "gotcha" is that it may have some control bits of
the power supply that are wired to two of the three phases, so if you
have the third phase bonded to one of the hot leads, and it doesn't
work, you may want to try bonding it to the other phase instead.
This, folks, is the Phase Rotation Sensor that he talks about, and
will cause a power check if not fooled.
Worrying about any sort of single to three phase
converter for a
modernish computer is just a waste of money. The only things that
truly need three phase (real or improvised) are things with three-phase
motors in them...
I would agree. This is what in my post a bit back was specific to
older machines - basically, before the switching power supply moved
into the picture, in the mid 1970s.
--
Will
12:47 p.m.
New subject: SGI Onyx [was] Re: VAXen at home - 3ph source/MG set?
On Oct 19, 2007, at 3:09 PM, JP Hindin wrote:
You know, it's ironic this topic has come up, as
I'm currently
working on
converting my 3ph SGI Onyx to single phase and had looked into
static and
rotary phase convertors. Having never had any reason to look at one
before
I started anew - and decided quickly that they did not appear to be
safe
for computer use.
Did you ever get your necessary power boards? I pulled the three
boards from my stock, I just was trying to get to the front of my
Onyx to check part numbers for you. If you got them, I won't bother
then.
Rob
Rob Borsuk
email: rborsuk at colourfull.com
Colourfull Creations
Web: http://www.colourfull.com
1:04 p.m.
New subject: SGI Onyx [was] Re: VAXen at home - 3ph source/MG set?
On Fri, 19 Oct 2007, Robert Borsuk wrote:
Wow, thanks Rob, I appreciate that. The list got quiet, so I assumed no
one was able to help out.
I've found a guy on Nekochan who is going to sell me the electrical board
that sits in for the CC3 midplane on a single-phase unit, three power
boards (512x2 and two 505x2), a System Controller and a Main I/O breakout
for $115. Although, I have to say, if I can -really- hook up the crazy
machine using three single phase hots, I might save myself some dosh on
the midplane replacement.
I greatly appreciate your time and effort, though, to help out, Rob. I
don't suppose you have an RE2 Graphics I/O breakout, maybe we can still
jive on something?
Thank you!
JP
You know,
it's ironic this topic has come up, as I'm currently
working on
converting my 3ph SGI Onyx to single phase and had looked into
static and
rotary phase convertors. Having never had any reason to look at one
before
I started anew - and decided quickly that they did not appear to be
safe
for computer use.
Did you ever get your necessary power boards? I pulled the three
boards from my stock, I just was trying to get to the front of my
Onyx to check part numbers for you. If you got them, I won't bother
then.
1:17 p.m.
New subject: SGI Onyx
On Oct 19, 2007, at 4:04 PM, JP Hindin wrote:
Wow, thanks Rob, I appreciate that. The list got
quiet, so I
assumed no
one was able to help out.
I've found a guy on Nekochan who is going to sell me the electrical
board
that sits in for the CC3 midplane on a single-phase unit, three power
boards (512x2 and two 505x2), a System Controller and a Main I/O
breakout
for $115. Although, I have to say, if I can -really- hook up the crazy
machine using three single phase hots, I might save myself some
dosh on
the midplane replacement.
I greatly appreciate your time and effort, though, to help out, Rob. I
don't suppose you have an RE2 Graphics I/O breakout, maybe we can
still
jive on something?
Thank you!
JP
JP,
Let's go off list. I have two 12's and a 5 volt board. You see,
bad Rob (that's me) had an RE2 Onyx gutted about 5 to 6 years ago.
It was in California and I just couldn't afford to freight it, but I
could afford to pay for and have the boards and breakouts shipped. I
should have enough base stuff to get you up and going. I can't give
them to you, but I'll make them way cheaper then the other guy. Or
we can always trade stuff (dig deep). Anyways, I'll shoot a bunch of
pictures of the insides for you this weekend.
Rob
Rob Borsuk
email: rborsuk at colourfull.com
Colourfull Creations
Web: http://www.colourfull.com
12:08 p.m.
My experience with these things (admittedly only with
machine tools)
shows a strong tendency for less-than-perfect (i.e. 120 degree) phase-
to-phase relationships and fairly drastic phase-to-phase voltage and
current variations. They work with motors, but none allows for full
motor nameplate loading (usually around 80 percent of nameplate). My
take is that they work "sort of". Heaven only knows how a power
supply would behave attached to one of these things.
I doubt it would be SO bad that the power supply would not work
properly. Most have constant voltage transformers to take care of
problems like this anyway, and if one of the phases is really out of
whack in the voltage department, it can be bucked or boosted with an
autotransformer.
A small phase shift in one of the phases really will not do much. Any
fans or pumps will basically not care (and help correct the error as
well). In a full three phase rectifier, the ripple just will not go
out of control if a phase if off even by 30 degrees. And if it is, put
another big cap or two in the circuit.
All this assumes that the three phase converter is not some little
wimpy motor, but something with a lot of balls. The bigger the
converter, the smaller the problems, but the larger the electric bill.
My feeling is that if you have to power some
three-phase big iron
from a single-phase source, it's probably better to take a look at
one of the modern (and expensive) solid-state converters--or get some
real three-phase distribution installed.
If the iron gets too big, it will suck up too much power for
reasonable use in a house anyway. The proper thing to do is buy or
rent some industrial space with real power.
--
Will
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26 comments
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participants (9)
-
cclist＠sydex.com -
ggs＠shiresoft.com -
jplist2007＠kiwigeek.com -
mouse＠Rodents.Montreal.QC.CA -
pat＠computer-refuge.org -
ploopster＠gmail.com -
rborsuk＠colourfull.com -
roger.holmes＠microspot.co.uk -
wdonzelli＠gmail.com