why 3-phase power?

[Jonathan Barnes]

<phil-news-nospam@ipal.net> wrote

Jonathan Barnes <jbarnes@atnetcomuk.co.uk> wrote:

| Well... the Europeans used 220V, the British used 240V, and we are all
now
| harmonising on a nominal 230V.

Is that with one hot leg or two? If you get three phase power there, what
are the common voltages?

One hot leg, 230V single phase, our three phase is formed from another two

230V phases at 120 degree phase angle to one another so we get 400V between
phases.

To keep the load even, it's common to run things like warehouse lights on
all three phases of the incoming supply.

another difference is we ( Europeans ) run at 50 Hz, while Americans use 60
Hz.

--
Jonathan

Barnes's theorem; for every foolproof device
there is a fool greater than the proof.

To reply remove AT

 

[Spehro Pefhany]

On Wed, 31 Dec 2003 08:42:58 +0000 (GMT), the renowned Tony Williams
<tonyw@ledelec.demon.co.uk> wrote:

In article <bam3vv8v5lr18ktiias5gi27lqr9mf0tr4@4ax.com>,
Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:

It better uses transformer iron and makes better/cheaper
induction motors. For making DC it requires less in the way of
filtering. It would be nice if we had something like 6 phase
power, we could get rid of the input filter caps in most
equipment, the only part that we can't make smaller by increasing
efficiency and frequency of SM power supplies.

Industrial-strength rectifiers do use transformers
sets that supply 6 phases.

Severe thread drift here...... An interesting use of
filterless multi-phase rectification was in amplitude
stabilising of RC oscillators. No filter cap meant
a fast response to changes, without bounce. Made
obsolete when cheap analogue multipliers came along,
(rectification via sine-squared_plus_cos-squared).

Interesting. Did that use a transformer arrangement using quadrature
input (wide frequency range) or some kind of RC kludge?


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[Keyboard In The Wildernes]

Some answers for you at URL:
http://lists.contesting.com/archives/html/Amps/2003-11/msg00208.html

--
73 From The Wilderness Keyboard
"Alan Horowitz" <alanh_27@yahoo.com> wrote in message
news:1e3670a7.0312300921.599776f8@posting.google.com...

what is the attraction of three-phase power? Why not 9 0r 317
phases? Why not plain ole hot & neutral?

 

[H. R. Bob Hofmann]

John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote in message news:<lKt8k4ATto8$EwBr@jmwa.demon.co.uk>...

I read in sci.engr.electrical.compliance that Matt Osborn
msosborn@spam_trap.?.net> wrote (in <clc4vvklhde4937050t1coj5isqs0p8t5i
@4ax.com&gt about 'why 3-phase power?', on Tue, 30 Dec 2003:
On Wed, 31 Dec 2003 08:11:59 +0900, "Brenda Ann"
brendad@shinbiro.com> wrote:


"Frank Bemelman" <fbemelx@euronet.invalid.nl> wrote in message
news:3ff1eb4a$0$166$3b62cedd@news.wanadoo.nl...
"Alan Horowitz" <alanh_27@yahoo.com> schreef in bericht
news:1e3670a7.0312300921.599776f8@posting.google.com...
what is the attraction of three-phase power? Why not 9 0r 317
phases? Why not plain ole hot & neutral?

9 phases.... 317 phases, have you ever wired a 317 prong plug?


In the US that would be a 319 prong plug.. 317 for the phases, one for
neutral, and one for ground.. LOL



But none for the little boy who cries in the lane?

The baa-baa black shield goes to the metal shell of the connector.

John Woodgate obviously has too much time and too little to do on this
New Year's Eve day.

Happy New Year to all who have contributed to this group over the past
year, no matter which side of the great ocean you live on.

H. R. (Bob) Hofmann (from the west side of the Atlantic)

 

[John Woodgate]

I read in sci.engr.electrical.compliance that H. R. Bob Hofmann
<hrhofmann@att.net> wrote (in <deadaa59.0312310713.354b738d@posting.goog
le.com&gt about 'why 3-phase power?', on Wed, 31 Dec 2003:

John Woodgate obviously has too much time and too little to do on this
New Year's Eve day.

Not so. I worked all over Christmas except on the day itself, when I
only had about an hour's discussion on balanced input stages and
headphone sound level control circuits. (;-)

As a result, the presentation that I'm working on has ground to a halt
because I can't concentrate. So I'm clearing up a few other jobs
instead. (More audio interconnection stuff and induction loops.)

But I ALWAYS make time for whimsy.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[Tim Wescott]

My initial reaction to that question was "goodness no!". Then, before I put
my foot in my mouth, I checked the Digi-Key catalog:

A Triad CME375-5 inductor for switched-mode power supplies is 28.6uH at
2.2A, and measures 32x38x30mm, for a volume of around 36cc. If you run it
right at it's current limit you can store (28.6uH)(2.2A)^2/2 = 70uJ
(micro-joules) of energy, or about 2 micro-joules/cc.

A Kemet T350E106K016A5 tantalum cap is 10uF, 16V, 5.5x5.5x8.9mm, volume =
0.27cc. Unlike an inductor which won't be permentantly damaged by
overcurrernt your cap will explode if it's subjected to overvoltage, so you
_never_ run it more than 10V. Given that you can store (10uF)(10V)^2/2 =
500uJ, or about 1800uJ/cc -- and capacitors are much less dense than
inductors, so they'll weigh less for the volume.

This is why, when you're designing a power supply with inductors (1MHz
switched or brute-force 60Hz), you usually design the inductor to have it's
current swing from nearly zero (or all the way to zero) up to nearly it's
maximum. This extracts nearly all the stored energy from the inductor each
cycle. On the other hand you use the capacitors to reduce ripple by having
their voltage vary a tiny fraction of the total, thereby letting lots of
energy just sit there doing no work.

"Frank Bemelman" <fbemelx@euronet.invalid.nl> wrote in message
news:3ff20970$0$23703$1b62eedf@news.wanadoo.nl...

That's a good point, the universal input. Is an inductor a better
storage for energy than a capacitor, I wonder, from a dimensions
point of view...

--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)

 

[John Larkin]

On 31 Dec 2003 01:34:14 GMT, phil-news-nospam@ipal.net wrote:

In sci.electronics.basics Spehro Pefhany <speffSNIP@interlogdotyou.knowwhat> wrote:
| On 30 Dec 2003 09:21:11 -0800, the renowned alanh_27@yahoo.com (Alan
| Horowitz) wrote:
|
|>what is the attraction of three-phase power? Why not 9 0r 317
|>phases? Why not plain ole hot & neutral?
|
| It better uses transformer iron and makes better/cheaper induction
| motors. For making DC it requires less in the way of filtering. It
| would be nice if we had something like 6 phase power, we could get rid
| of the input filter caps in most equipment, the only part that we
| can't make smaller by increasing efficiency and frequency of SM power
| supplies.

Actually, you can get 6 and even 12 phases out of 3 phases fairly easily.
If you put a normal single primary to center tapped secondary (120/240 in
North America) on each of the three phases (tie all the neutrals together),
you really have 6 phases.

Once you have the basic six phases, the addition of small "interphase
transformers" or windings here and there can create any number of
additional phases at small added expense. 24 phase rectifiers are
common in big DC systems.

John

 

[Spehro Pefhany]

On Wed, 31 Dec 2003 10:23:56 -0800, the renowned John Larkin
<jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote:

Once you have the basic six phases, the addition of small "interphase
transformers" or windings here and there can create any number of
additional phases at small added expense. 24 phase rectifiers are
common in big DC systems.
John

Might you find that sort of thing on a ship?

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

In sci.electronics.basics Jonathan Barnes <jbarnes@atnetcomuk.co.uk> wrote:
|
| <phil-news-nospam@ipal.net> wrote
|>Jonathan Barnes <jbarnes@atnetcomuk.co.uk> wrote:
|>
|> | Well... the Europeans used 220V, the British used 240V, and we are all
| now
|> | harmonising on a nominal 230V.
|>
|> Is that with one hot leg or two? If you get three phase power there, what
|> are the common voltages?
|>
| One hot leg, 230V single phase, our three phase is formed from another two
| 230V phases at 120 degree phase angle to one another so we get 400V between
| phases.
|
| To keep the load even, it's common to run things like warehouse lights on
| all three phases of the incoming supply.
|
| another difference is we ( Europeans ) run at 50 Hz, while Americans use 60
| Hz.

At least Europe can share power around the continent as needed. Japan is
split frequency (50 Hz in the east, 60 Hz in the west) making that much
harder to do. I guess that's why they came up with all the 50/60 Hz stuff
and the 100-250 volt ranges (their voltage is 100/200).

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------

 

In sci.electronics.basics John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote:
| I read in sci.engr.electrical.compliance that Jonathan Barnes
| <jbarnes@ATnetcomuk.co.uk> wrote (in <bsss8k$56l$1@taliesin2.netcom.net.
| uk&gt about 'why 3-phase power?', on Tue, 30 Dec 2003:
|
|>I belive the American system is 2 x 110 V ac lines with respect to earth,
|>but at 180 degree phase angle, to give 220 V ac potential between them.
|>
|>I would say it's fair to call this 2 phase.
|
| So do other people, but it's an inflammatory issue with some US experts.

It's called "2 pole".

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------

 

[Michael A. Terrell]

John Woodgate wrote:

But I ALWAYS make time for whimsy.
--
Regards, John Woodgate

And bad puns! ;-)

--
Merry Christmas!

Take care, and God bless.
Michael A. Terrell
Central Florida

 

[John Woodgate]

I read in sci.engr.electrical.compliance that Michael A. Terrell
<mike.terrell@earthlink.net> wrote (in <3FF343A5.D88872E5@earthlink.net>
) about 'why 3-phase power?', on Wed, 31 Dec 2003:

John Woodgate wrote:

But I ALWAYS make time for whimsy.
--
Regards, John Woodgate

And bad puns! ;-)

There are no bad puns, but some are worse than others. Puns about German

sausages are the Wurst.

Seasonal felicitations.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[Rich Grise]

"Jonathan Barnes" <jbarnes@ATnetcomuk.co.uk> wrote in message
news:bssv5m$5je$1@taliesin2.netcom.net.uk...

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message

I belive the American system is 2 x 110 V ac lines with respect to
earth,
but at 180 degree phase angle, to give 220 V ac potential between them.

120V, but close enough.

Ah... thats why some american equipment I had did not like running on a
110V
safty transformer I had for testing

110V should be within the tolerance - IOW, it wasn't the lower voltage that
it didn't like running on, but something else. Typically "120V" equipment
can
run from 105-125.

I would say it's fair to call this 2 phase.

Not fair, just WRONG, though I can see that electricians who think of
"phase" as equivalent to "hot wire" might find it okay. True two phase
could be converted to 3, 6 or whatever phase using Scott-T
transformers.

3 phase supplies have a 120 degree phase angle between them.

Not true for this, which is just a center-tapped 240V
line. You can go right or left on a one-dimensional line from zero,
but it's still in one dimension..

I would hate to have you navigate for me if you don't see a diference
between left and right...

No, he can tell the difference between right and left. It's still one
dimension.

The difference is the difference between right/left and up/down, or
right/left, up 120 deg down 300 deg, up 240 deg. down 420 deg. for
3-phase.

But a center-tapped transformer gives you ONE PHASE. There is no
phase rotation, it's simply the inversion.

Take, for example, a pulse train:

- - - - -
| | | | | | | | | |
--- ----- ----- ----- ----- ---
Now, invert it:
--- ----- ----- ----- ----- ---
| | | | | | | | | |
- - - - -

This is clearly _NOT_ the original shifted 180 degrees.

_THIS_
- - - - - -
| | | | | | | | | | |
----- ----- ----- ----- ----- ---

is the original shifted 180 degrees.

Can you kids now see the difference between a 180 degree
phase shift and a simple inversion?

Thank you.
Rich

 

[John Larkin]

On Wed, 31 Dec 2003 18:34:57 GMT, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

On Wed, 31 Dec 2003 10:23:56 -0800, the renowned John Larkin
jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote:

Once you have the basic six phases, the addition of small "interphase
transformers" or windings here and there can create any number of
additional phases at small added expense. 24 phase rectifiers are
common in big DC systems.
John

Might you find that sort of thing on a ship?

Best regards,
Spehro Pefhany

Dunno... most of my shipboard experience was on steam turbine plants.
Some ships are diesel-electrics, so may have big rectifiers somewhere.
I have seen 24-phase SCR supplies driving motors or something, but I
can't recall where... locomotives maybe.

Lots of ships are diesel these days, because the plants are small,
simple, and reliable compared to steam. Many are direct, 1:1 shaft
drive using reversible diesels. Many ships have small electric "take
home" motors powered off the aux diesel generators.

John

 

[Rich Grise]

"Frank Bemelman" <fbemelx@euronet.invalid.nl> wrote in message
news:3ff1eb4a$0$166$3b62cedd@news.wanadoo.nl...

"Alan Horowitz" <alanh_27@yahoo.com> schreef in bericht
news:1e3670a7.0312300921.599776f8@posting.google.com...
what is the attraction of three-phase power? Why not 9 0r 317
phases? Why not plain ole hot & neutral?

9 phases.... 317 phases, have you ever wired a 317 prong plug?

Sadly, yes. At least it seemed like it - a multi-signal connector deep

within the bowels of the fuselage of an F-4 Phantom Jet, just above
the exhausts, sitting/lying/crouching on a bed-of-nails of sheet metal
screws poking through the skin of the airplane. I had to do the work
because I was the one who found the break with a TDR. It wasn't that
bad - holding the connector and wire and replacement pin with one
hand, the Tech Order with the other hand, the flashlight with the other
hand, the soldering iron with the other hand, the solder in my teeth;
And don't forget the crimping tool and Cannon Plug Pliers.

I remember following the wire bundle along the skin, where other crews
had taken off the panels, and reached a point where it took a 90 deg.
turn directly into the fuselage. I said to my cow-orker, "It's
4 feet from here, that way." pointing toward the centerline of the
airplane. He said, "Have fun!" It took three other guys just to remove
all the crap to get access to where the connector was. (things like
"control feel bellows" and linkages and fuel and hydraulic lines and
wires, and wires, and wires...)

Cheers!
Rich

 

[John Woodgate]

I read in sci.engr.electrical.compliance that Rich Grise
<spamdump@nowhere.net> wrote (in <6LHIb.34499$E17.33149@nwrddc02.gnilink
..net&gt about 'why 3-phase power?', on Wed, 31 Dec 2003:

Can you kids now see the difference between a 180 degree
phase shift and a simple inversion?

Not on a sine wave, no. But it's a futile discussion: neither opinion
will ever be abandoned.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[John Larkin]

On Wed, 31 Dec 2003 15:58:55 +0000, John Woodgate
<jmw@jmwa.demon.contraspam.yuk> wrote:

But I ALWAYS make time for whimsy.

A little nonsense now and then
Is relished by the wisest men.

- Willy Wonka



John

 

[Jonathan Barnes]

Rich Grise wrote

Can you kids now see the difference between a 180 degree
phase shift and a simple inversion?

Not as long as SIN X = - SIN ( X + 180 )

There is no difference with a sine wave.

Can you give me details of any test you use to detect the difference ?


--
Jonathan

Barnes's theorem; for every foolproof device
there is a fool greater than the proof.

To reply remove AT

 

In sci.electronics.basics John Larkin <jjlarkin@highsniplandthistechpleasenology.com> wrote:
| On 31 Dec 2003 01:34:14 GMT, phil-news-nospam@ipal.net wrote:
|
|>In sci.electronics.basics Spehro Pefhany <speffSNIP@interlogdotyou.knowwhat> wrote:
|>| On 30 Dec 2003 09:21:11 -0800, the renowned alanh_27@yahoo.com (Alan
|>| Horowitz) wrote:
|>|
|>|>what is the attraction of three-phase power? Why not 9 0r 317
|>|>phases? Why not plain ole hot & neutral?
|>|
|>| It better uses transformer iron and makes better/cheaper induction
|>| motors. For making DC it requires less in the way of filtering. It
|>| would be nice if we had something like 6 phase power, we could get rid
|>| of the input filter caps in most equipment, the only part that we
|>| can't make smaller by increasing efficiency and frequency of SM power
|>| supplies.
|>
|>Actually, you can get 6 and even 12 phases out of 3 phases fairly easily.
|>If you put a normal single primary to center tapped secondary (120/240 in
|>North America) on each of the three phases (tie all the neutrals together),
|>you really have 6 phases.
|>
|
| Once you have the basic six phases, the addition of small "interphase
| transformers" or windings here and there can create any number of
| additional phases at small added expense. 24 phase rectifiers are
| common in big DC systems.

But you can go straight to 12 phases from 3 phases. Your power feed needs
to have a wye configuration (most common) and you need to be able to deal
with some phases having a different voltage than others. For a DC power
supply you use 3 transformers to get 6 phases, but you can get 12 phases
out of 6 transformers all having primaries attached to various combinations
of the 4 wires coming from the wye secondary of the utility transformer
secondary. These still need to be mixed voltage (on the primary of the DC
power supply transformers). The voltages in the US would be 120/208 or
277/480 or 347/600 depending on what your utility can provide.

Now once you have 12 phase power, then more transformers can give you even
more phases, and not just twice as many. What you can get now depends on
the individual secondary voltages, which don't have to be all the same, and
can give you a very interesting mix of phase possibilities. The OP mentioned
300+ phases. That could probably be accomplished with several transformers.

I don't see much need for motors above 3 phases and certainly not above 12.
But DC power supplies might still get very good use of a lot of phases. One
thing I've wondered is if a big zener (bank) can "clip off" a small ripple
that a 12 phase power supply would have and virtually eliminate capacitors.

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------

 

[Tony Williams]

In article <j5o5vv8u2jk7uq0pcpsl2t0bdpkaa33a77@4ax.com>,
Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:

On Wed, 31 Dec 2003 08:42:58 +0000 (GMT), the renowned Tony
Williams <tonyw@ledelec.demon.co.uk> wrote:
Severe thread drift here...... An interesting use of
filterless multi-phase rectification was in amplitude
stabilising of RC oscillators.

Interesting. Did that use a transformer arrangement using
quadrature input (wide frequency range) or some kind of RC
kludge?

You have to start with a 2-phase oscillator for the
the basic Sin/Cos. Then lots of resistors and opamps
to get multiple arithmetic phase-shifted outputs. ISTR
that at about 8-phase rectification the harmonic
distortion effect of the residual ripple is sufficiently
attenuated by the oscillator itself.

--
Tony Williams.