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'[EE:] 110v olt motors on 230v mains'
2005\02\22@124513 by John Pearson

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I need to run 4, maybe 6, 12 amp motors at once. I can get them in 230v or 110v. I would prefer 110 volt motors.

Now, since my cloths dryer is on a 40amp 230v circuit, would there be anything wrong with powering maybe 2 or 3 motors off one 110v side of the 230v circuit, and the other 2 or 3 motors off the other 110v side of the 230v circuit?
Thanks
John

2005\02\22@143904 by Brenden McNeil

picon face
There is nothing at all wrong with that.  Although, usually, 230v
motors are more effecient and require less amps.


On Tue, 22 Feb 2005 09:58:39 -0800, John Pearson <spam_OUTxeroTakeThisOuTspamcmc.net> wrote:
> I need to run 4, maybe 6, 12 amp motors at once. I can get them in 230v or 110v. I would prefer 110 volt motors.
>
> Now, since my cloths dryer is on a 40amp 230v circuit, would there be anything wrong with powering maybe 2 or 3 motors off one 110v side of the 230v circuit, and the other 2 or 3 motors off the other 110v side of the 230v circuit?
>
> Thanks
> John
> -

2005\02\22@144822 by Marc Nicholas

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On Tue, 22 Feb 2005, Brenden McNeil wrote:

> There is nothing at all wrong with that.  Although, usually, 230v
> motors are more effecient and require less amps.

Huh? What makes you say that?

Of course you require less amps at 230vac than 120vac for the same
work...but do you really mean your require less energy overall? (i.e.
Watts).

-marc

2005\02\22@150554 by olin_piclist

face picon face
Marc Nicholas wrote:
> but do you really mean your require less energy overall? (i.e.
> Watts).

Hopefully not, since Watts is a unit of power, not energy.

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2005\02\22@151336 by Brenden McNeil

picon face
In some cases yes it may consume less watts.  It's rather negligable
and would depend on the varoius motor.  If you look at most heavy duty
woodworking equipment, you'll find mostly 220 motors.



On Tue, 22 Feb 2005 14:36:36 -0500 (EST), Marc Nicholas
<.....marcKILLspamspam@spam@geekythings.com> wrote:
{Quote hidden}

> -

2005\02\22@155141 by Scott Fraser

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John,

First off, my answers are based on wiring in US and there may be slight
variations if you are not under the US NEC (National Electric Code)

Yes you can do this providing you meet a number of conditions.
Dryer outlets.  These outlets are many times two hots (230V) and a
grounding conductor.
The grounding conductor is an equipment grounding conductor and is not
allowed to operate as a current carrying conductor.  It is for fault
current only.
If you have only three wires on your dryer outlet, you only have a
grounding conductor there and this cannot be used.

Other dryer outlets have four conductors, there are two types of four wire
connections
Connection type #1
two hots (230V)
a grounding conductor (discussed above, green in color)
a grounded conductor, often called a neutral conductor and either white or
gray in color and smaller gauge than the hots.

The grounded conductor (neutral) on a dryer outlet is allowed to be smaller
gauge wire than the hot conductors based on the premise that the heating
coils will use 230V and the neutral is provided so that 120V can be
connected to things like digital displays, clocks, oven lamps.

In this case, the neutral conductor will not be of sufficient gauge to
carry the 40amps that it will see if you have only one set of motors running.

Connection Type #2
two hots (230V)
a grounding conductor (discussed above, green in color)
a grounded conductor, (neutral conductor) and SAME gauge as the hots.

Now if you connection type #2, we can get to work.

Number of motors allowed.
Your 40 amp circuit can only be loaded to a maximum of 32 amps on a
continuous basis.  With two lines, each fully loaded to 32 amps you could
run a maximum of five motors at one time.

Distance.
How far from the connection point for the motors is your entrance
panel?  With heavy current draws that the motor startup currents will
subject the line to, you need to make sure that you will not see more than
3% voltage drop on a heavily loaded line.

Hope that helps,

Scott


At 09:58 AM 2/22/05, you wrote:
>I need to run 4, maybe 6, 12 amp motors at once. I can get them in 230v or
>110v. I would prefer 110 volt motors.
>
>Now, since my cloths dryer is on a 40amp 230v circuit, would there be
>anything wrong with powering maybe 2 or 3 motors off one 110v side of the
>230v circuit, and the other 2 or 3 motors off the other 110v side of the
>230v circuit?
>
>Thanks
>John
>

2005\02\22@161747 by Stephen R Phillips

picon face

--- John Pearson <xerospamKILLspamcmc.net> wrote:

> I need to run 4, maybe 6, 12 amp motors at once. I can get them in
> 230v or 110v. I would prefer 110 volt motors.
>
> Now, since my cloths dryer is on a 40amp 230v circuit, would there be
> anything wrong with powering maybe 2 or 3 motors off one 110v side of
> the 230v circuit, and the other 2 or 3 motors off the other 110v side
> of the 230v circuit?
>
Not a problem, just be sure to bring a BIG white neutral in.
Why do you want to use 110 instead of 230? Voltage problem? Wiring issues?


               
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2005\02\22@172719 by Peter van Hoof

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One additional concern with 110 volt instead of 220, should the
neutral conductor ever develop a bad connection you run the risk
of destroying one or more of the connected motors. At my current
employers this happened to a stack of 8 motorcontrollers
connected in star to a 3 phase feed, the neutral terminal on a
rail was loose and 5 of them failed resulting in a few thousand $
loss.

Peter van Hoof

{Original Message removed}

2005\02\22@183417 by Roy J. Tellason

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On Tuesday 22 February 2005 03:55 pm, Scott Fraser wrote:
{Quote hidden}

I've *never* seen the neutral wire be of a gauge different from the others...

> The grounded conductor (neutral) on a dryer outlet is allowed to be smaller
> gauge wire than the hot conductors based on the premise that the heating
> coils will use 230V and the neutral is provided so that 120V can be
> connected to things like digital displays, clocks, oven lamps.

Or the motor in a lot of cases.  In this house,  the dryer outlet is wired to
two-gang breakers,  but in older houses that used fuses it was quite common
to hear the complaint that "the dryer spins but won't heat",  meaning one of
the fuses was blown but not the other one.

{Quote hidden}

Where'd you get that percentage figure from?

> Hope that helps,
>
> Scott

Of course,  then you have people who mess with this stuff that *REALLY* don't
know what the hell they're doing.  Like what I found when I looked into
complaints from the family downstairs (stepson, his wife, and grandkids),  
where they were "getting shocked by the dryer".

The outlet at the drier and was wired correctly,  so I pulled the cover to the
breaker box.  Where I found black and white (neutral!) connected to the two
poles of the dual-gang breaker,  and red (hot2!) along with the grounding
conductor tied to the ground block.

Idiots!







2005\02\22@195331 by olin_piclist

face picon face
Brenden McNeil wrote:
> In some cases yes it may consume less watts.  It's rather negligable
> and would depend on the varoius motor.  If you look at most heavy duty
> woodworking equipment, you'll find mostly 220 motors.

But that's because of the overall power requirement making the current too
high to handle easily at 110V.  I don't think that 220V is inherently better
than 110V for magnetic motors.  Unlike some other things like light bulbs
which inherently want to be low voltage and high current devices.  In other
words, magnetic windings to produce mechanical force can be designed over a
wide latitude of voltage and current at the same force.


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2005\02\22@220351 by Peter van Hoof

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> I've *never* seen the neutral wire be of a gauge different from
> the others...

While I have not seen this myself either it would have to be
thicker because it would carry double the current  of the other
conductors.


Peter van Hoof


2005\02\22@235903 by Dave Tweed

face
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Peter van Hoof <.....peterKILLspamspam.....whacky-scientist.com> wrote:
> > I've *never* seen the neutral wire be of a gauge different from
> > the others...
>
> While I have not seen this myself either it would have to be
> thicker because it would carry double the current  of the other
> conductors.

Nope. Think about where the current goes in the worst-case conditions and
you'll see why not!

-- Dave Tweed

2005\02\23@014237 by Scott Fraser

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At 07:01 PM 2/22/05, you wrote:
>>I've *never* seen the neutral wire be of a gauge different from the others...
>
>While I have not seen this myself either it would have to be thicker
>because it would carry double the current  of the other conductors.

Worst case is current between one hot and neutral.  The neutral gauge is
the same as the hot wire gauge.

In the case where you have motors running off of both hots, the neutral
will carry the difference current.
10 amps on hot A and 7 amps on hot B, the neutral will be carrying 3 amps.

In some Wye (120/208) four wire distributions, you MAY find the neutral
conductor larger than the three hots to handle harmonic currents created by
many of the switching power supplies found in office equipment.

Scott

2005\02\23@015816 by Scott Fraser

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At 03:32 PM 2/22/05, you wrote:
> > Distance.
> > How far from the connection point for the motors is your entrance
> > panel?  With heavy current draws that the motor startup currents will
> > subject the line to, you need to make sure that you will not see more than
> > 3% voltage drop on a heavily loaded line.
>
>Where'd you get that percentage figure from?

2002 National Electric Code  (California is still on 1999)
210.19(A)(1) FPN No. 4
3% max voltage drop for branch circuits and
5% max voltage drop for branch circuits and feeders combined.

Scott

2005\02\23@035726 by ThePicMan

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At 14.36 2005.02.22 -0500, you wrote:


>On Tue, 22 Feb 2005, Brenden McNeil wrote:
>
>>There is nothing at all wrong with that.  Although, usually, 230v
>>motors are more effecient and require less amps.
>
>Huh? What makes you say that?
>
>Of course you require less amps at 230vac than 120vac for the same work...but do you really mean your require less energy overall? (i.e. Watts).

Well, Joule effects are of less concern on the higher voltage.. but of course this can be compensated for..

2005\02\23@074031 by olin_piclist

face picon face
Peter van Hoof wrote:
> While I have not seen this myself either it would have to be
> thicker because it would carry double the current  of the other
> conductors.

No, because the return currents from the two 110V legs are out of phase and
will therefore cancel.  The neutral wire only handles the difference between
the two 110V hot wires, which means worst case it needs to handle the same
current as a hot lead if the entire load is only on one of the 110V phases.


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(978) 742-9014, http://www.embedinc.com

2005\02\23@113201 by alan smith

picon face

Remember....when you start the motor you are going to
see a surge in current before it settles down to its
lower current draw. You might want to sequence these
motors up such that your breaker doesn't pop when they
all come on.  Also keep in mind that the neutral wire
is going to be carrying twice the current now so make
sure its sized correctly.  I'm assuming that each leg
is actually the same phase....



               
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2005\02\23@113745 by alan smith

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No...it doesnt have to be.  Someone mentioned this
before...

the heaters will derive its power across the two legs
of the 220V, and the motor and other things in the
dryer will just tap off one leg of the 220 and the
neutral. Typically its a 30A or 40A circuit, so more
than enough to run a small motor off the 120V.  Thats
why the neutral can be the same size as the feeds.

But in this case, he will NEED to run a double size
neutral to handle the return currents.

That being said....why not run some dedicated 220V
circuits since we already know the existing neutral
won't really handle it.




--- Peter van Hoof <EraseMEpeterspam_OUTspamTakeThisOuTwhacky-scientist.com> wrote:

{Quote hidden}

> --

2005\02\23@114304 by alan smith

picon face
I'm thinking...this is "bi-phase" or two phase and
just  two taps off the main transformer so they should
be in phase.  The transformer is 3phase, but for
typical residential drops, they use only one set of
the windings?  Thus both 220V legs should be in phase.

Also, of you do attach a device across two legs of a
3phase service, so there isnt a neutral present, the
return current is additive.  In other words, take a
208Y service.  Attach a power supply across phase A
and B and then another across phases B and C.  If the
current draw is 1A, you will see 2A on phase B since
it shares between the two devices.


--- Olin Lathrop <olin_piclistspamspam_OUTembedinc.com> wrote:

{Quote hidden}

*****************************************************************
> Embed Inc, embedded system specialists in Littleton
> Massachusetts
> (978) 742-9014, http://www.embedinc.com
> --

2005\02\23@115047 by Dave Tweed

face
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alan smith <@spam@micro_eng2KILLspamspamyahoo.com> wrote:
> But in this case, he will NEED to run a double size
> neutral to handle the return currents.
>
> That being said....why not run some dedicated 220V
> circuits since we already know the existing neutral
> won't really handle it.

Where do you guys get this stuff from?

There is no combination of loads that can cause the the neutral current
to exceed the current in either of the hot legs alone. It is *always*
sufficient to have the neutral the same gauge as the hot legs in this
type of circuit.

Work it out! (And pay attention to the phase relationships!)

-- Dave Tweed

2005\02\23@121901 by Brenden McNeil

picon face
This is very correct.

On Wed, 23 Feb 2005 07:40:08 -0500, Olin Lathrop
<KILLspamolin_piclistKILLspamspamembedinc.com> wrote:
{Quote hidden}

> -

2005\02\23@123147 by olin_piclist

face picon face
alan smith wrote:
> I'm thinking...this is "bi-phase" or two phase and
> just  two taps off the main transformer so they should
> be in phase.  The transformer is 3phase, but for
> typical residential drops, they use only one set of
> the windings?  Thus both 220V legs should be in phase.

No, that's not how it works.  Yes, a house is fed from one of the three
phases of the transmission system.  This drives the primary of a
transformer.  The secondary is 220V center tapped.  The center is connected
to a solid earth ground right at your house usually as close as reasonable
to the breaker panel.  In my house this is about a 1/2 inch copper rod
driven into the ground.

The normal 110V house circuits are between one end of the secondary and the
center.  Such breaker panels have two columns of breakers side by side, with
each column driven from a different end of the 220V winding.

220V circuits, like for a dryer or electric range, are wired accross the
whole secondary.  Therefore with respect to ground, a 220V connection is
really two 110V feeds at 180deg out of phase.  Think about it.  If they were
in phase there would never be a voltage difference between them.

> Also, of you do attach a device across two legs of a
> 3phase service, so there isnt a neutral present, the
> return current is additive.  In other words, take a
> 208Y service.  Attach a power supply across phase A
> and B and then another across phases B and C.  If the
> current draw is 1A, you will see 2A on phase B since
> it shares between the two devices.

Not exactly.  The two currents are 120deg out of phase, which is 60deg off
from being exactly opposite.  Part of the current from each phase cancels.

When working with multiple phases, you have to take phase angle into account
and can't just add voltages and currents as if they were scalars.


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2005\02\23@125411 by alan smith

picon face
But...for a residential service, are both legs on the
same phase? Or out of phase?  

If out of phase, yes I do agree....return currents
will be out of phase as well and no issues on the size
of the neutral.

IF in phase...there is the issue.


--- Dave Tweed <RemoveMEpicTakeThisOuTspamdtweed.com> wrote:

{Quote hidden}

> --

2005\02\23@131849 by David Minkler

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Alan,

If they were in phase with the same amplitude, there would be no
potential difference between them.

Dave

alan smith wrote:

{Quote hidden}

2005\02\23@135647 by olin_piclist

face picon face
alan smith wrote:
> But...for a residential service, are both legs on the
> same phase? Or out of phase?
>
> If out of phase, yes I do agree....return currents
> will be out of phase as well and no issues on the size
> of the neutral.
>
> IF in phase...there is the issue.

This has been answered about three times already.  THINK about it.  If both
110V feeds were in phase, they would be no use in making 220V since the
voltage between them would always be 0.


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(978) 742-9014, http://www.embedinc.com

2005\02\23@140204 by Herbert Graf

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face
On Wed, 2005-02-23 at 09:54 -0800, alan smith wrote:
> But...for a residential service, are both legs on the
> same phase? Or out of phase?  
>
> If out of phase, yes I do agree....return currents
> will be out of phase as well and no issues on the size
> of the neutral.
>
> IF in phase...there is the issue.

I have never seen a residential service where they are in phase. Most
residential I've seen in Canada are simply the outputs of a center
tapped transformer, the center tap goes to neutral, and the two "hots"
are your two phases, 180 degrees from each other.

Some residential (mostly apartment buildings/condos) are supplied three
phase, so each unit gets two of the three phases (hence the fact that
both 240/220 and 208 appliances exist in North America.

In fact, two legs, of the same phase, will sum to zero, so you'd never
be able to run 220 stuff off those two legs. Only with 120 loads would
you end up with twice the current. That is a config I've never seen (two
hots sharing one neutral) and I wouldn't be surprised if it was against
most codes. TTYL

-----------------------------
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2005\02\23@145049 by Dave Tweed

face
flavicon
face
olin_piclist@embedinc.com (Olin Lathrop) wrote:
> The normal 110V house circuits are between one end of the secondary and
> the center.  Such breaker panels have two columns of breakers side by
> side, with each column driven from a different end of the 220V winding.

Almost right. The taps are actually interleaved within the columns;
otherwise, you wouldn't be able to plug in a dual breaker for a 220V
circuit at all.

-- Dave Tweed

2005\02\23@151311 by Mike Hord

picon face
Okay, here's a statement of what I'm understanding of this.
Perhaps one message summing up what I've drawn will help
everyone get on the same page.

At all times, assume I'm speaking of the United States, since
this seems to be focused on a residence in the USA.

Power is distributed 3-phase.  For a house, a single phase is
connected to the the primary of a transformer.  The secondary
is 220V center tapped.  The center tap forms the neutral,
which is tied to a large copper rod driven into the earth nearest
the box where the power enters the house.  The center tap
then continues to the breaker panel, where it is distributed into
the rest of the house as a white wire.  A green (or bare) wire is
tied to the ground rod at the rod, then distributed to the rest of
the house as a green (or bare) wire.  The 220V legs come in
through a large breaker, then are redistributed, seperately, as
110V, to each circuit in the house.  220V loads are placed
across the two legs of the secondary.  Some 220V connectors
provide the neutral as well, to allow independent sections of a
220V device to use 110V.

This is where I start to get hazy.  As I see it, Ohm's law and
phasor diagrams tell me that one leg is 110V, or (110 + 0j)V,
and the other is 110V at an angle of 180 deg, or (-110 + 0j)V.
The implication there is that no load, reactive, resistive, or any
combination of the two, could produce currents in phase with
one another such that the current through the neutral wire
exceeds the current through either of the hot wires.  Resistive
loads will be out of phase with one another, reactive loads
introduce a j term which still doesn't help the basic fact of
the two voltages being 180 deg out of phase, and since on
their own, neither is a solution, the sum of two non-solutions
also fails to be a solution.

One other thing puzzles me.  What good does it do to tie
the neutral to the ground rod outside, then run two seperate
wires to each outlet?  Is the benefit derived from the fact that
the green/bare wire is nominally supposed to be a
non-current-carrying wire?  That proves helpful in ground-fault
detection schemes, but how so otherwise?

Mike H.

2005\02\23@152827 by Herbert Graf

flavicon
face
On Wed, 2005-02-23 at 14:13 -0600, Mike Hord wrote:
> One other thing puzzles me.  What good does it do to tie
> the neutral to the ground rod outside, then run two seperate
> wires to each outlet?  Is the benefit derived from the fact that
> the green/bare wire is nominally supposed to be a
> non-current-carrying wire?  That proves helpful in ground-fault
> detection schemes, but how so otherwise?

Actually this one is very simple: safety.

Consider this: you have a computer with a metal chasis. The metal
chassis is normally connected to the green wire. Consider there's a
fault in the supply that causes the hot to hit the chassis: boom,
breaker blows, all is good.

Now consider the case where there is no green wire: you have two
choices:

- connect the chassis to nothing (you can easily see what happens if you
happen to touch the chassis with hot in contact with the chassis).

- second choice - connect the chassis to the neutral. Sounds good right
since the neutral is connected to the same point as ground used to be
connected. But, what happens if the neutral wire is broken somewhere in
the house? The computer won't turn on. What will you do? Probably end up
touching the chassis, which is now at pretty much line voltage (even if
the PC power supply switch is on all it takes is one device on that
neutral leg to be on, a light bulb will do it). Not a good end for
you...

TTYL


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2005\02\23@160109 by olin_piclist

face picon face
Dave Tweed wrote:
> Almost right. The taps are actually interleaved within the columns;
> otherwise, you wouldn't be able to plug in a dual breaker for a 220V
> circuit at all.

Hmm.  That makes sense, but I also remember seeing two copper bus bars going
down either side of the breaker box, each fed from one of the thick 200A hot
cables coming in from the top.  I'll have to look at my breaker box more
closely when I get home tonight.


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2005\02\23@174659 by Mike Hord

picon face
> - second choice - connect the chassis to the neutral. Sounds good right
> since the neutral is connected to the same point as ground used to be
> connected. But, what happens if the neutral wire is broken somewhere in
> the house? The computer won't turn on. What will you do? Probably end up
> touching the chassis, which is now at pretty much line voltage (even if
> the PC power supply switch is on all it takes is one device on that
> neutral leg to be on, a light bulb will do it). Not a good end for
> you...

So does this imply that the ground wire doesn't follow the same route as
the neutral and hot do, to avoid both neutral and ground being severed?

Not to argue against safety, but it seems to me that most things (say,
careless use of a reciprocating saw) which would sever the neutral will
also sever the hot, and ground, too, if they take the same path.

Mike H.

2005\02\23@181240 by Dave Tweed

face
flavicon
face
Mike Hord <TakeThisOuTmike.hordEraseMEspamspam_OUTgmail.com> wrote:
> One other thing puzzles me.  What good does it do to tie
> the neutral to the ground rod outside, then run two seperate
> wires to each outlet?  Is the benefit derived from the fact that
> the green/bare wire is nominally supposed to be a
> non-current-carrying wire?  That proves helpful in ground-fault
> detection schemes, but how so otherwise?

Herbert has already answered the basic question, but I want to expand on
it a little.

When homes were first wired with electricity (using knob-and-tube
technology -- I actually live in a house that's that old), no part of the
transformer secondary was grounded. The whole thing just "floated" and all
wires were treated as equally dangerous. In theory, grounding any single
point within the system would not cause any fault current to flow.

However, it was quickly discovered that for a number of reasons (a
combination capacitive coupling and resistive leakage in the pole
transformer), the secondary would end up at several hundred to several
thousand volts relative to ground, creating a dangerous situation if an
appliance had a short to its case. Therefore, it was decided to ground
the center tap of the secondary at a single point to drain off this
leakage current. This became the "grounded" or "neutral" conductor.

But appliance faults could still put 110V on exposed parts. You might
argue that if the neutral was already bonded to the case, this would
cause a short and blow the fuse/breaker. But keep in mind that the
grounded conductor is not truly at ground potential -- it has finite
resistance, and the load current can cause the voltage at the appliance
to be significantly different from ground. If there are other grounded
objects nearby, a person touching both could still receive lethal
currents.

Therefore, it was decided to add a third, "grounding" conductor that
must not intentionally carry load currents at any time. A fault in an
appliance will still cause the breaker to trip, but in normal operation,
the voltage on the case is the same as all other grounded objects.

A ground fault current detector does NOT actually use the grounding
conductor. It works by measuring any difference in the currents carried
by the hot and neutral conductors. If this does not add up to zero, then
there must be current flowing directly to ground somewhere (and not
necessarily through the grounding conductor), so it trips.

-- Dave Tweed

2005\02\23@191312 by p.cousens

flavicon
also Re: the centre taped earth, What this does is ensure that any
contact with
a single conductor, will only give you a max 110 volts shock making you
safer for you

> One other thing puzzles me.  What good does it do to tie
> the neutral to the ground rod outside, then run two seperate
> wires to each outlet?  Is the benefit derived from the fact that
> the green/bare wire is nominally supposed to be a
> non-current-carrying wire?  That proves helpful in ground-fault
> detection schemes, but how so otherwise?
>
> Mike H.
> --

2005\02\23@211336 by Cnc002

picon face
In a message dated 2/23/05 7:48:33 AM Eastern Standard Time,
RemoveMEolin_piclistspamTakeThisOuTembedinc.com writes:

> No, because the return currents from the two 110V legs are out of phase and
> will therefore cancel.  The neutral wire only handles the difference between
> the two 110V hot wires, which means worst case it needs to handle the same
> current as a hot lead if the entire load is only on one of the 110V phases.
>

Dead on,  even in three phase applications the neutral is the same size as
the hot lines.  But, in most cases the ground line is smaller and that is
allowed by code for the most part.  However, personally I prefer to have my ground
the same as the other wiring, just a preference of mine.

Regarding house wiring, you are just using 2 leads of the three phase line
and then using a center tapped transformer to create the neutral and therefore
110 Vac for most home applications.  In that case because the 220 lines are out
of phase, then the neutral can be the same size as the hot leads.  Now, if
you have 220 volts with no neutral, just the two hot leads and you are not
certain if there is a neutral somewhere in the circuit that is attached to ground,
then you will NOT get 110 between those 220 volt lines and ground, it will be
the 220 divided by the square root of 3, or close to that.  However, if you
are in an industrial area and happen to have a "Y" configuration then you should
have a neutral and you would get 110 between one of the legs and the neutral,
as long as it is NOT 440 three phase of course.  Now, having said all of
that, one can often operate 110 volt devices even on the higher voltage between
ground and one of the three phase lines as many 110 devices are rated 120 and
can often handle a 10% variation in voltage.  You would get something like 125
to 130 volts between one leg of a 220 three phase line and ground, if there is
no neutral.

Hope this helps and doesn't confuse.

Randy Abernathy

4626 Old Stilesboro Road NW
Acworth, GA 30101
Ph / Fax: 770-974-5295
E-mail: cnc002EraseMEspam.....aol.com

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.

2005\02\23@221639 by Herbert Graf

flavicon
face
On Wed, 2005-02-23 at 16:46 -0600, Mike Hord wrote:
> > - second choice - connect the chassis to the neutral. Sounds good right
> > since the neutral is connected to the same point as ground used to be
> > connected. But, what happens if the neutral wire is broken somewhere in
> > the house? The computer won't turn on. What will you do? Probably end up
> > touching the chassis, which is now at pretty much line voltage (even if
> > the PC power supply switch is on all it takes is one device on that
> > neutral leg to be on, a light bulb will do it). Not a good end for
> > you...
>
> So does this imply that the ground wire doesn't follow the same route as
> the neutral and hot do, to avoid both neutral and ground being severed?
>
> Not to argue against safety, but it seems to me that most things (say,
> careless use of a reciprocating saw) which would sever the neutral will
> also sever the hot, and ground, too, if they take the same path.

Yes, in which case you're safe since the hot would short to the neutral
and/or ground and the breaker would trip.

However, it does make sense. A current carrying wire will go through
stresses a non current carrying wire will go through. It's actually more
common then some would think for things like screws to come loose in the
panel and sever the connections of either the hot or neutral.

On top of that, if you have a bad connection on a neutral it's entirely
possible for it to be at a dangerous potential above ground.

Suffice it to say if there weren't a valuable benefit on the safety
front we wouldn't be wasting a TON of money on running three wires
instead of two. TTYL


-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

2005\02\24@072231 by Lee Jones

flavicon
face
>> No, because the return currents from the two 110V legs are
>> out of phase and will therefore cancel.  The neutral wire
>> only handles the difference between the two 110V hot wires,
>> which means worst case it needs to handle the same current as
>> a hot lead if the entire load is only on one of the 110V phases.

> Regarding house wiring, you are just using 2 leads of the three
> phase line and then using a center tapped transformer to create
> the neutral and therefore 110 Vac for most home applications.

When I read this, it implied (to me) that the electric company
was bringing 2 legs of the 3 phase power that appears on the pole
into the residence.

In all the cases I've worked on (southwestern US), the electric
company uses 3 phase delta wiring on the pole (or underground);
3 wires, each hundreds or thousands of volts, and 120 degrees
out of phase with the waveform on the other 2 conductors.

Any 2 legs are used as the primary feeding a transformer that
serves 4 to 16(?) houses.  (Ttransformer is frequently called a
pole pig.)  Primary side floats.  If done correctly, the next
transformer is connected to the "next" leg pair so that the
overall load for a city (as seen by the generators) is equal
across all 3 phases.

Secondary side is 240V, single phase, center tapped.  Center
tap is tied to ground at the pole.  It should also be tied to
ground at the breaker panel.  Each hot leg has 120V measured
to the center tap (neutral/ground).  240V center tap power is
distributed to adjacent houses via an additional 3 wires on
the same poles (but seperate than the 3 wires carrying 3 phase
primary power on those poles).

Very odd results when the neutral line breaks.

Rambling personal story, hopefully amusing, follows.

After a wind storm, appliances and lights in the house across
the street were behaving very oddly.  Electric utility had so
many repairs they were estimating 4-5 days before they could
get to it.  The neighbors asked me to look at it.

I was seeing 60 volts to 150 volts on various outlets in the
house.  And it would vary depending on what lights and/or
appliances were running.  I suspected a bad neutral.

Power drop from utility pole was 3 conductors -- 2 insulated
hot lines wrapped around an uninsulated steel bearer cable.
Transformer center tap on pole is tired to ground and is
carried by steel bearer cable.  House breaker panel's neutral
was NOT tied to local earth ground.  Uninsulated steel bearer
cable was the house's only neutral connection.

Wind had flexed bearer cable until it broke.  House had 2 hot
lines coming in with local (breaker panel) neutral bus bar
floating at a level set by ratio between active loads of the
house's lights & appliances (i.e. a big resistance divider
with hundreds of volts & a couple dozen amps).

I used a rope to physically relieve stress on hot conductors
by pulling drop cable towards house entry point.  And I used a
car battery jumper cable to electrially bond across the break
in the broken steel bearer wire.  Problem solved.  House ran
that way for about 4 days.  Edison (electric utility) service
man thought it was creative when he arrived and properly
repaired the drop cable.

I explained to the owners that they should fix the lack of a
local ground on their breaker panel.  Not sure if they ever
did so.

                                               Lee Jones

2005\02\24@080223 by Dave Tweed

face
flavicon
face
Lee Jones <EraseMEleespamfrumble.claremont.edu> wrote:
> In all the cases I've worked on (southwestern US), the electric
> company uses 3 phase delta wiring on the pole (or underground);
> 3 wires, each hundreds or thousands of volts, and 120 degrees
> out of phase with the waveform on the other 2 conductors.
>
> Any 2 legs are used as the primary feeding a transformer that
> serves 4 to 16(?) houses.  (Ttransformer is frequently called a
> pole pig.)  Primary side floats.  If done correctly, the next
> transformer is connected to the "next" leg pair so that the
> overall load for a city (as seen by the generators) is equal
> across all 3 phases.

Around here (New England), they apparently use a wye-connected
distribution system, typically at 6000V, with the center of the
wye grounded (not floating). When you see an industrial customer
getting three-phase power, it's clear that the three transformers
are wye-connected to the feeders.

All three phases run along the larger streets, but often just a
single wire runs down a side street, feeding several pole pigs,
which are connected between the wire and ground. Different streets
are on different phases, distributing the load so that presumably
there isn't a huge ground current flowing back to the substation.
There is usually a bare ground wire running along the very tops of
the poles (partly for lightning protection, I think), and it is
tied to a ground stake at every pole that carries a transformer.

-- Dave Tweed

2005\02\24@114537 by Mike Hord

picon face
> Therefore, it was decided to add a third, "grounding" conductor that
> must not intentionally carry load currents at any time. A fault in an
> appliance will still cause the breaker to trip, but in normal operation,
> the voltage on the case is the same as all other grounded objects.
>
> Therefore, it was decided to add a third, "grounding" conductor that
> must not intentionally carry load currents at any time. A fault in an
> appliance will still cause the breaker to trip, but in normal operation,
> the voltage on the case is the same as all other grounded objects.
> Excellent.  I think most of what I had worked out was pretty close to
> right.

My rockstar cousin has an OLD (~40 years) tube based guitar amp
which frequently delivers tremendous shocks to other guitarists if
the touch him while holding their guitar at the same time.  No 3rd
wire!

I've also heard plenty of tales from my family (who all live or lived in
old-style wiring houses for a long time) about receiving nasty shocks
by touching the fridge and stove at once, or the fridge and sink.  I
presume that's from the floating voltage on the neutral.

Mike H.

2005\02\24@145128 by jrem

picon face
<snip>
> > right.
>
> My rockstar cousin has an OLD (~40 years) tube based guitar amp
> which frequently delivers tremendous shocks to other guitarists if
> the touch him while holding their guitar at the same time.  No 3rd
> wire!

That's not good, a three wire cord needs to be installed with the
ground bonded to the chassis, the hot into the fused switch, into the
power tranny, then to neutral (keeping mains off the tranny when
switched off).  That is probably the most common mod to old tube guitar
amps and it doesn't depreciate their value.

In effect you have up to 110vac between you and the other piece of
equipment (a microphone, other musician, etc).  At the low end is
difference between ground potential and neutral.  It's gotta go.



<snip>


               
__________________________________
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2005\02\24@205416 by Cnc002

picon face
In a message dated 2/24/05 11:47:10 AM Eastern Standard Time,
RemoveMEmike.hordEraseMEspamEraseMEgmail.com writes:

> My rockstar cousin has an OLD (~40 years) tube based guitar amp
> which frequently delivers tremendous shocks to other guitarists if
> the touch him while holding their guitar at the same time.  No 3rd
> wire!
>
> I've also heard plenty of tales from my family (who all live or lived in
> old-style wiring houses for a long time) about receiving nasty shocks
> by touching the fridge and stove at once, or the fridge and sink.  I
> presume that's from the floating voltage on the neutral.
>
> Mike H.
>

The condition you describe was very common back when they only had the 2
prongs.  If the outlet were wired backwards, the device still worked but if you
touched the metal housing of it and the metal housing of another appliance that
had it's plug wired correctlly you got shoced, the full 110 to 120 Volts no
less.  The manufacurers connected the neutral wire of the plug to the chassis of
the appliance in most cases, thus you got shocked.  Now of course the chassis
is connected to the ground wire, that 3rd wire of course and very seldom do
we get shocked anymore.

Thank goodness.

Randy Abernathy

4626 Old Stilesboro Road NW
Acworth, GA 30101
Ph / Fax: 770-974-5295
E-mail: RemoveMEcnc002spam_OUTspamKILLspamaol.com

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.

2005\02\24@230250 by Dwayne Reid

flavicon
face
At 06:54 PM 2/24/2005, RemoveMECnc002TakeThisOuTspamspamaol.com wrote:

>The condition you describe was very common back when they only had the 2
>prongs.  If the outlet were wired backwards, the device still worked but
>if you
>touched the metal housing of it and the metal housing of another appliance
>that
>had it's plug wired correctlly you got shoced, the full 110 to 120 Volts no
>less.  The manufacurers connected the neutral wire of the plug to the
>chassis of
>the appliance in most cases, thus you got shocked.  Now of course the chassis
>is connected to the ground wire, that 3rd wire of course and very seldom do
>we get shocked anymore.

As a person who worked on many (way too many!) of those amplifiers 30 or so
years ago, I'd like to correct the above statement:  one side of the line
cord was NOT connected directly to the chassis!

However, there was a fairly large capacitor from one side of the line to
chassis - something on the order of 0.1uF / 600V.  Most musical instrument
amplifiers also had a "ground" switch that switched the capacitor to the
other side of the incoming line or reversed the line polarity.  Fender was
big on this - a center-off power switch.

The idea was to reduce hum and noise by referencing to the closest thing
they could get to earth ground: the neutral line.  But plugs weren't
polarized and one had a 50/50 chance of getting it right.

However, you are right in that most AC powered tube-type consumer
electronics used hot chassis wiring: the old "All American 5" radios, most
of the recent (in those days) tube-type television sets (those without
power transformers).  But anything that required a consumer to be able to
actually touch circuit ground (such as guitar and PA amplifiers) did NOT
use a hot chassis connection.

dwayne

PS - Of course, that cap from line to chassis might have failed shorted . . .

dwayne

--
Dwayne Reid   <EraseMEdwaynerspamspamspamBeGoneplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 21 years of Engineering Innovation (1984 - 2005)
 .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-
    `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'   `-'
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
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2005\02\25@014232 by Cnc002

picon face
In a message dated 2/24/05 11:04:43 PM Eastern Standard Time,
RemoveMEdwaynerKILLspamspamplanet.eon.net writes:

> As a person who worked on many (way too many!) of those amplifiers 30 or so
>
> years ago, I'd like to correct the above statement:  one side of the line
> cord was NOT connected directly to the chassis!
>

Fact is, that in refrigerators, stoves, and many other home appliances, that
neutral wire WAS attached directly to the chassis.  I have repaired many of
those over the years.  Electronic devices were indeed different due to the hum
as you mention.

Randy Abernathy

4626 Old Stilesboro Road NW
Acworth, GA 30101
Ph / Fax: 770-974-5295
E-mail: cnc002STOPspamspamspam_OUTaol.com

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.

2005\02\25@094335 by Bob Ammerman

picon face
> After a wind storm, appliances and lights in the house across
> the street were behaving very oddly.  Electric utility had so
> many repairs they were estimating 4-5 days before they could
> get to it.  The neighbors asked me to look at it.
>
> I was seeing 60 volts to 150 volts on various outlets in the
> house.  And it would vary depending on what lights and/or
> appliances were running.  I suspected a bad neutral.
>
<snip>

> I explained to the owners that they should fix the lack of a
> local ground on their breaker panel.  Not sure if they ever
> did so.
>
> Lee Jones

Of course such a local ground is not likely to correct this problem
completely. The impedance of that ground is not likely to be low enough to
avoid a significant switch of the neutral's voltage. Grounding at the
utility pole and the residence is only intended to be sure that the neutral
is at zero potential to ground, when no (or minimal) current is flowing in
the grounding conductors. It is for this reason that the required conductor
size for this grounding conductor is _much_ smaller than the service
conductors. In fact, a situation where a significant neutral current were
forced thru the grounding conductor might be unsafe in and of itself.

Bob Ammerman
RAm Systems


2005\02\25@114632 by Mike Hord

picon face
> However, there was a fairly large capacitor from one side of the line to
> chassis - something on the order of 0.1uF / 600V.  Most musical instrument
> amplifiers also had a "ground" switch that switched the capacitor to the
> other side of the incoming line or reversed the line polarity.  Fender was
> big on this - a center-off power switch.

Next time I pay him a visit I'll check on the cap.

It does have the "ground" switch, and that usually fixes the problem.

It's kind of amusing, though, in the sense that anything with possibly
fatal repercussions can be.  Usually, the contact is a brief brushing
against one another, and can be quite startling.  I think a bigger
danger is touching something that is actually properly grounded...

Mike H.

2005\02\25@144015 by Robert Rolf

picon face
They'd be more efficient at 230V since the I^2R losses
would be less with a lower operating current.
You would save watts be having less heating.
R

Olin Lathrop wrote:

{Quote hidden}

2005\02\25@190433 by olin_piclist

face picon face
Robert Rolf wrote:
> They'd be more efficient at 230V since the I^2R losses
> would be less with a lower operating current.
> You would save watts be having less heating.

Not really.  Consider a coil producing a certain strength magnetic field at
220V.  Now consider how to create the same magnetic field with 110V starting
with that coil.  If you cut the coil in half, you have two 110V coils each
producing half the required magnetism.  To run these at 110V, you have to
put them in parallel instead of series.  Each individual coil has the same
current and therefore the same I^2R losses, and the total magnetism and
power are the same.

This is what I meant in that there is great latitude in how coils can be
wound to produce the same magnetism at different voltages.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\02\26@060125 by Mike Hawkshaw

flavicon
face
From: "Olin Lathrop"
Subject: Re: [EE:] 110v olt motors on 230v mains


> Robert Rolf wrote:
> > They'd be more efficient at 230V since the I^2R losses
> > would be less with a lower operating current.
> > You would save watts be having less heating.
>
> Not really.  Consider a coil producing a certain strength magnetic field
at
> 220V.  Now consider how to create the same magnetic field with 110V
starting
> with that coil.  If you cut the coil in half, you have two 110V coils each
> producing half the required magnetism.  To run these at 110V, you have to
> put them in parallel instead of series.  Each individual coil has the same
> current and therefore the same I^2R losses, and the total magnetism and
> power are the same.

But, you have 2 coils in parrallel, so there are twice the I^2R losses
overall...

Think about why we use high voltage to transfer power - because for a given
power P=VI at the end of the line, if you double the volts, you half the
current. If you half the current, you loose 1/4 of the power you would have
lost.

Cheers.....Mike.



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2005\02\26@184004 by Dwayne Reid

flavicon
face
At 05:04 PM 2/25/2005, Olin Lathrop wrote:
>Robert Rolf wrote:
>>They'd be more efficient at 230V since the I^2R losses
>>would be less with a lower operating current.
>>You would save watts be having less heating.
>
>Not really.  Consider a coil producing a certain strength magnetic field at
>220V.  Now consider how to create the same magnetic field with 110V starting
>with that coil.  If you cut the coil in half, you have two 110V coils each
>producing half the required magnetism.  To run these at 110V, you have to
>put them in parallel instead of series.  Each individual coil has the same
>current and therefore the same I^2R losses, and the total magnetism and
>power are the same.

But you have ignored the effects of transmission losses *to* the
motor.  Less current in those feeder lines means either lower losses for a
given wire size or smaller conductors for the same losses - allowing the
choice of lower installation costs or lower operating costs.

FWIW - probably the very first job I had when starting out in the
electrical trade was helping pull new (larger) conductors to a recently
installed large woodworking machine - the unit was tripping the breaker on
start-up because it took too long to reach full speed.  The journeyman who
had done the original install wanted to just install a larger breaker but
our boss (master electrician) insisted the proper way to fix was to pull in
larger conductors.  He got his way (he was the boss, after all) and larger
conductors did in fact fix the problem.  Quite a lesson for me and my first
exposure to the meaning of "back EMF" as it applies to electric motors.

dwayne

--
Dwayne Reid   <spamBeGonedwaynerSTOPspamspamEraseMEplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 21 years of Engineering Innovation (1984 - 2005)
 .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-.   .-
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2005\02\26@191343 by olin_piclist

face picon face
Mike Hawkshaw wrote:
> But, you have 2 coils in parrallel, so there are twice the I^2R losses
> overall...

No.  Look at each coil individually.  Let's say each coil draws 1A at 110V,
and the DC resistance is 500mOhm.  That means 500mW is lost in heat in each
coil.

If you drive the two coils in parallel from 110V, each coil sees 110V, draws
1A, and dissipates 500mW for a total of 1W.

If you drive the coils in series from 220V, each coil sees 110V, draws 1A,
and dissipates 500mW for a total of 1W.

Same thing.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\02\26@200806 by olin_piclist

face picon face
Dwayne Reid wrote:
> But you have ignored the effects of transmission losses *to* the
> motor.

Right.  We were talking about losses in the coils.  The original discussion
was about 220V versus 110V *motors* being more efficient.  Of course any
power delivery is more efficient at higher voltage for the reason you
mentioned, but that has nothing to do with the efficiency of the load, and
is certainly not limited to motors.  Chosing a delivery voltage is a set of
tradeoffs, one of which is that higher voltage allows lower current, which
causes less loss in the transmission system.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\02\28@060224 by Mike Hawkshaw

flavicon
face
From: "Olin Lathrop"
Subject: Re: [EE:] 110v olt motors on 230v mains


> Mike Hawkshaw wrote:
> > But, you have 2 coils in parrallel, so there are twice the I^2R losses
> > overall...
>
> No.  Look at each coil individually.  Let's say each coil draws 1A at
110V,
> and the DC resistance is 500mOhm.  That means 500mW is lost in heat in
each
> coil.
>
> If you drive the two coils in parallel from 110V, each coil sees 110V,
draws
> 1A, and dissipates 500mW for a total of 1W.
>
> If you drive the coils in series from 220V, each coil sees 110V, draws 1A,
> and dissipates 500mW for a total of 1W.
>
> Same thing.

Of course, you're right. Thanks for making it clear(er). It is only losses
in transmission that make any difference.

Cheers...Mike.



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2005\02\28@145613 by Roy J. Tellason

flavicon
face
On Saturday 26 February 2005 07:13 pm, Olin Lathrop wrote:
> Mike Hawkshaw wrote:
> > But, you have 2 coils in parrallel, so there are twice the I^2R losses
> > overall...
>
> No.  Look at each coil individually.  Let's say each coil draws 1A at 110V,
> and the DC resistance is 500mOhm.  That means 500mW is lost in heat in each
> coil.
>
> If you drive the two coils in parallel from 110V, each coil sees 110V,
> draws 1A, and dissipates 500mW for a total of 1W.
>
> If you drive the coils in series from 220V, each coil sees 110V, draws 1A,
> and dissipates 500mW for a total of 1W.
>
> Same thing.

But what you guys are not considering here is the drop in the wires getting to
that point -- running at 110V is going to draw twice as much current,  but
there will be _four times_ as much power wasted as heat,  since it's
I<squared>R...

_That_ is the efficiency of using 220V for bigger loads.







'[EE:] 110v olt motors on 230v mains'
2005\03\01@110056 by Cnc002
picon face


In a message dated 2/28/2005 2:57:04 PM Eastern Standard Time,  
KILLspamrtellasonspamBeGonespamblazenet.net writes:

But what  you guys are not considering here is the drop in the wires getting
to
that  point -- running at 110V is going to draw twice as much current,  but  
there will be _four times_ as much power wasted as heat,  since it's  
I<squared>R...

_That_ is the efficiency of using 220V for  bigger loads.




Yep, this is true and one of the reasons for using 460 volts where  possible,
three phase of course,  not to mention you can use much smaller  wiring and
other circuit components such as breakers, motor overloads,  etc.

Just my thoughts.


Randy  Abernathy
4626 Old Stilesboro Road NW
Acworth, GA 30101-4066
Phone /  Fax: 770-974-5295
Mobile: 678-772-4113
E-mail:  EraseMEcnc002spamEraseMEaol.com

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.

2005\03\01@123830 by Mike Hawkshaw

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face
Subject: Re: [EE:] 110v olt motors on 230v mains

> Yep, this is true and one of the reasons for using 460 volts where
possible,
> three phase of course,  not to mention you can use much smaller  wiring
and
> other circuit components such as breakers, motor overloads,  etc.

The real advantage of three phase is that it the most efficient way of
transmitting power, taking into account the copper losses, and the cost of
more conductors to go to more phases.

I have a proof of this somewhere in my 17 year old course notes on
electricity and magetism which are all in the loft, absolutely thick with
dust.

Mike.



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2005\03\01@142656 by Cnc002

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In a message dated 3/1/2005 12:48:54 PM Eastern Standard Time,
@spam@mike@spam@spamspam_OUTspikey-mike.com writes:
The real advantage of three phase is that it the most efficient way of
transmitting power, taking into account the copper losses, and the cost of
more conductors to go to more phases.

I have a proof of this somewhere in my 17 year old course notes on
electricity and magetism which are all in the loft, absolutely thick with
dust.
You are absolutely correct.  If you compare horsepower for horsepower between
a single phase motor and a three phase motor the total current draw is MUCH
less for the three phase unit.  I was just referring to the voltage in my
earlier post, but mentioned the three phase because, well, it is not easy to find
460 volt single phase applications, if you know what I mean.

One of my professors at Georgia Tech, used the analogy of a single cylinder
engine versus a multi-cylinder engine as a simplistic way to give an example of
single phase versus three phase.

Everyone have a great and blessed day.

Randy Abernathy
4626 Old Stilesboro Road
Acworth, GA 30101
Ph / Fax: 770-974-5295
E-mail: spamBeGonecnc002spamKILLspamaol.com

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.

2005\03\01@152419 by olin_piclist

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Mike Hawkshaw wrote:
> The real advantage of three phase is that it the most efficient way of
> transmitting power, taking into account the copper losses, and the cost
> of more conductors to go to more phases.

The real point behind 3 phase power is that total power delivered is
constant and does not vary with the 60Hz or 50Hz power cycle.  Three phases
is the minimum required for this to be true.  Among other things, this means
that the torque on the generators at power plants is constant.  This is very
important for such high power machines.  This also means that 3 phase motors
draw a constant power and put out a constant torque.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\03\01@160600 by Cnc002

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In a message dated 3/1/2005 3:32:20 PM Eastern Standard Time,  
.....olin_piclistspam_OUTspamembedinc.com writes:

The real  point behind 3 phase power is that total power delivered is
constant and  does not vary with the 60Hz or 50Hz power cycle.  Three phases
is the  minimum required for this to be true.  Among other things, this  means
that the torque on the generators at power plants is constant.   This is very
important for such high power machines.  This also means  that 3 phase motors
draw a constant power and put out a constant  torque.



This is true, and yes, it is a major reason you use three phase  motors on
industrial machinery, we use them in almost all applications no matter  how
small the power requirement.  Some of the axis positioning motors for  "go to and
stop" axis positioning use motors as small as 1/8 Hp with  electro-mechanical
brakes on them.  Can you imagine what the power usage  would be using single
phase motors, some of which would need to be 200 Hp or so  and say 50 to 60 of
those 1/8 Hp motors on a single machine.  Wouldn't want  to pay that power
bill.

Another thing that is good about 3 phase is the ability to virtually  reverse
thier direction instantaneously and of course how easy it is to do that,  
simply two of the wires using a second motor starter, etc.  As well as  reduced
starting currents by using wye-delta starting, no special transformers,  
electronics, etc. needed in most applications.



Randy  Abernathy
4626 Old Stilesboro Road NW
Acworth, GA 30101-4066
Phone /  Fax: 770-974-5295
Mobile: 678-772-4113
E-mail:  TakeThisOuTcnc002.....spamTakeThisOuTaol.com

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.

2005\03\01@170306 by Peter L. Peres

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> In a message dated 2/28/2005 2:57:04 PM Eastern Standard Time,
> TakeThisOuTrtellasonKILLspamspamspamblazenet.net writes:
>
> But what  you guys are not considering here is the drop in the wires getting
> to
> that  point -- running at 110V is going to draw twice as much current,  but
> there will be _four times_ as much power wasted as heat,  since it's
> I<squared>R...

And what you save in the distribution wiring you lose in the price of
the equipment and I^2*R losses in it, since it is now wound with thinner
wire on account of lower current and more turns to avoid saturation ?

Peter

2005\03\02@132328 by Peter L. Peres

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On Tue, 1 Mar 2005, Olin Lathrop wrote:

{Quote hidden}

Afaik it takes two phases for that. Proof: instantaneous power for a
sin, cos 2-phase system, at 90 degrees is:

Pi = (U1*sin(wt)*I1*sin(wt)) + (U2*sin(wt+pi/2)*I2*sin(wt+pi/2))

with U1=U2 and I1=I2 this becomes:

Pi = 2*U*I*(sin(wt)^2 +cos(wt)^2) = 2*U*I*1

I think that the real real reason why 3 phases are 'better' is the
better use of copper and iron. For 2 phases one still needs 3 wires and
one of them would have to be thicker. With 3 phases they can be equal.
Also the torque of a 3-phase machine is more constant than a 2-phase
machine's although I doubt that this applies to any sizeable generator,
those having in the hundreds or even thousands of poles and
phasing/equalizing gear downstream to prevent imbalance between the
phase loads.

Peter

2005\03\02@135732 by olin_piclist

face picon face
Peter L. Peres wrote:
> Afaik it takes two phases for that.

Yeah, you're right.  I just repeated what I remembered from a brief lecture
on power electronics a long time ago, but your math makes sense.  I do
remember something about 3 phases required for constancy of something, but
apparently not power.

One advantage that 3 phase has the 2 phase doesn't is that all three phasers
add to zero.  To get constant power with 2 phases they need to be separated
by 90 degrees with the resulting vector sum definitely not zero.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\03\03@000606 by Russell McMahon

face
flavicon
face
Roy

I didn't see you original message, but I understand that you are
unhappy with the low PIC content of the PICList and high OT volume.

The PICList is an utterly superb PIC resource. You are unlikely to
find better expertise and helpfulness anywhere on earth. BUT you need
to know how to drive it properly.

The PICList is arranged to meet a wide variety of needs.
If you want to largely PIC only content then setting your options so
you get only the [PIC] tag will achieve this. There will be SOME
spillover into the PIC channel BUT if it goes on too long it will get
moved onto another tag.

Simlarly [EE] is good fro electrical engineering.

Then there's my kingdom :-) - the [OT] tag which is a wide range of
subject material is acceptable. The FAQ explains the linmits.
Basically none of what you'd expect. (Hardcore politics, religion, sex
/ NO personal abuse or derrogation (as in all tags) ). I'm also EE
active and a very little PIC as well. On OT I largely try to bring
material which others are lible to find informative and / or
interesting.

If you read the FAQ and the message you got when you joined youi
should be able to set things up the way you want.


regards

           Russell McMahon





2005\03\03@103636 by Cnc002

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Also, in many cases the EE tag helps with interfacing PIC projects to the
real world as there is often information in those posts that can be applied even
though they weren't directed toward a specific PIC subject.

Randy Abernathy
4626 Old Stilesboro Road
Acworth, GA 30101
Ph / Fax: 770-974-5295
E-mail: .....cnc002spamRemoveMEaol.com

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.

2005\03\04@162630 by Peter L. Peres

picon face


On Wed, 2 Mar 2005, Olin Lathrop wrote:

{Quote hidden}

I don't understand that but in any case power machinery will have torque
output and that is a function of current. So you could argue that the
ripple in the sum current between the instantaneous currents on 3 phases
doing work is lower than on 2 phases doing work. I also know that some
applications which require rectification for high poewer used 6 phases
(30 degrees apart) for the same reason. Aluminium smelting was one (?).
This may no longer be true.

Peter

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