just call it 2 phase

[Twayne]

You can have 2 phases at 90 degrees. Or you can have 2 phases at 120
degrees. Or you can have 2 phases at 109.70519 degrees. Or you can
have 2 phases at 180 degrees. It's still 2 vector angles relative to
the reference point, which is generally the grounded conductor.
Trying to avoid referring to two phases as two phases just because
their angle happens to be 180 degrees is just stubbornheadedness. If
you need to specifically say what the angles are because the angles
matter, then say it. But there's really no reason we can't refer to
the type of power system supplying most homes in the USA as two phase
power.

Or just call it Split Phase as everyone in the industry does, and be
done with it.

 

[[email protected]]

| [email protected] wrote:
|> You can have 2 phases at 90 degrees. Or you can have 2 phases at 120
|> degrees. Or you can have 2 phases at 109.70519 degrees. Or you can
|> have 2 phases at 180 degrees. It's still 2 vector angles relative to
|> the reference point, which is generally the grounded conductor.
|> Trying to avoid referring to two phases as two phases just because
|> their angle happens to be 180 degrees is just stubbornheadedness. If
|> you need to specifically say what the angles are because the angles
|> matter, then say it. But there's really no reason we can't refer to
|> the type of power system supplying most homes in the USA as two phase
|> power.
|>
|>> WARNING: Due to extreme spam, googlegroups.com is blocked. Due to
|>> ignorance | by the abuse department, bellsouth.net is
|>> blocked. If you post to | Usenet from these places, find
|>> another Usenet provider ASAP. |
|>> Phil Howard KA9WGN (email for humans: first name in lower case at
|>> ipal.net) |
|
| Or just call it Split Phase as everyone in the industry does, and be
| done with it.

What I have encountered is that fewer than half understand this term.
Lots of people already call it 2 phase. In a purely technical aspect,
it really is 2 phases. Sometimes the phase angle is 180 degrees. And
sometimes it is 120 degrees. When it is 120 degrees do you still call
it Split Phase?

I'm suggest "2 phase" for all cases of having 2 phases regardless of the
degree angle. This includes not only the "Edison style split single phase"
but also the "Got only 2 phases out of the 3 phase service" which is just
"2 phases at 120 degrees", as well as "corner grounded open delta" which
is "2 phases at 60 degrees" and can mimic 3 phase delta for many purposes.
There is also "2 phase at 90 degrees". If it's a 3 wire system where one
is a grounded conductor or otherwise considered to be the neutral reference
point, and the other 2 have a phase angle other than 0 degrees, I call it
a "2 phase" system. That's a broad classification. It can be narrowed
down by describing it further, such as the number of degrees.

Lots of people do NOT understand "split phase". This number seems to be
greater than the number that do NOT understand "2 phase".

 

[[email protected]]

| [email protected] writes:
|
|>| 90 degree 2 phase (the 3 wire version, anyway) does not, however, have a
|>| zero neutral current when balanced.
|
|>The optimal system design that has both a flat power waveform and is balanced
|>with zero neutral current is 3 phase. Mr. Tesla figured that out a while back.
|
| Yes. That's why everything is 3 phase today.

Except for the places that have certain forms of 2 phase (180 or 120 degree)
or just 1 phase.

 

[Don Kelly]

| phases are 360/2 degrees apart. 3 phase 360/3 degrees apart, 4 phase
| 360/4 etc.

That would be the normal way of thinking of it. It gets interesting when the
number of phases is any even number. For example 6 phase. I have mentioned
the concept of 6 phase before and some people get confused. If a 6 phase
system with phases labeled A,B,C,D,E,F (going around the circle) with phase
angles of 360/6 degrees each, gives you 240 volts between A and D, then why
can't a subsystem tapped from just A and D alone be called 2 phase? They are
counted as 2 phases.

That depends on how you look at it- if you bring out only the two
terminals A,D you have a single voltage between them. It is then
indistinguishable from a single phase 2 wire supply. With a single
voltage, phase, as a relative term, becomes a problem. as what do you
relate this single voltage to?
If the 6 phase system is a Y rather than a polygon (super delta) then
you have a neutral and then you can consider that you have a 2 phase
system where the voltages Van and Vbn are 180 degrees apart. You then
have 3 terminals. This is indistinguishable from the center tapped
single phase system which fits what the Europeans refer to as 2 phase.
Neither are distinguishable from a 2 wire single phase system if you
ignore the neutral.

we are getting into "Yah, But.." territory here.

 

[Don Kelly]

Not when you look at the delivered power to an ideal resistive load.

Not really- remembering that we consider the power delivered to be the
average power.

Polyphase power is almost always taught by plotting the voltage waveform
of each leg. All EEs are familiar with 3 phase power where one phase has
a voltage sinewave with a positive zero crossing at 0 degrees, a second
phase has the same voltage waveform with a positive zero crossing at 120
degrees, the third identical but at 240 degrees. IMO, this is a mistake
that leads to the "is-the-Edison-system-single-phase-or-2-phase" flamewars.

-----
If one has been through single phase AC analysis and phasor
relationships, this plotting is nice but not at all necessary.
polyphase voltage relationships- not power relationships are often shown
that way-and this is useful-. but then one gets into application of
phasors as previously learned in single phase analysis.

If, instead, we hook up N identical ideal resistors to the polyphase system
and plot the power delivered to each of them, we also get sinewaves, but
at twice the frequency, and shifted up so that the negative most excusion
is at 0. (it goes negative for reactive loads but let's ignore them)

So far what you say is also valid for single phase. Normally, however,
one goes from this presentation of the instantaneous power to a
mathematical formulation and from this to average power per cycle- which
is what is generally referred to as "power" and the relationship of this
average power to rms voltages and currents is shown. Power factor is
related to this as well. When we consider a 240V 60Hz source, the
voltage is then generally expressed as an rms voltage and the power
delivered to a resistive load as calculated from (Vrms^2)/R is the
average power- which is also what a wattmeter measures..

If we plot 3 phase power this way we still get 3 power waveforms shifted
at 0, 120, 240 degrees (when using the double frequency, or at 0, 60, 120
degrees if we use the original frequency scale). If we plot 90 degree 2
phase we still get two power waveforms at 90 degrees. However, the Edison
system produces 2 /identical/ power waveforms, completely different from
the other polyphase systems. There's only one power phase.

I see what you are getting at. It is not something fundamentally
different because the instantaneous power in this case is proportional
to the square of the instantaneous voltage so that the power waveform is
always positive, even when the voltage is negative. So when you have two
voltages 180 degrees out of phase (as you have in the Edison system-
measuring with respect to the neutral), the power waveforms will peak at
the same time for equal loads on each leg.
Now consider a two phase system with the voltages measured with respect
to a neutral which are x degrees apart, Now let x approach 180 degrees
and there will be a phase difference between the instantaneous power
waveforms that gets progressively smaller until it becomes 0 when the
voltages are exactly 180 degrees apart. There is no fundamental change
that takes place.
In terms of average power per phase and total power- no change exists.
Note also that if you look at the total power waveform rather than the
individual legs- then the waveform that you will get will be
indistiguishable from the single phase or the 2 phase case except for
magnitudes for the same phase voltages and resistive loads per phase. In
terms of average powers (using rms voltages) the average power will be
directly proportional to the number of phases for equal phase voltages
and loads.

This makes any any even number of phase system questionable. For example,
the "six phase" system mentioned by others. It's really three phase in
disguise. You could produce a /different/ six phase system with each of
the 6 power waveforms shifted by equal amounts, just like you can produce
90 degree two phase by shifting the power by 90 degrees. Like 90 degree 2
phase, it's not symmetrical (you can't plot the 6 voltage waveforms
symmetrically, just like with 90 degree 2 phase there's a neutral current
for a balanced load. For each of them you can connect the center tap of
the transformer secondaries as the neutral and bring out the 180 degree
voltage waveform/"the other leg", and you'd probably call it "12 phase"
(or "4 phase" for the 90 degree 2 phase system) and get the symmetrical
voltages. It's still only 6 power phases (2 for "4 phase"/90 degree 2
phase) I've heard the "4 phase" system called 4 or 5 wire 90 degree 2
phase, depending on whether the neutral is supplied to the load. For 4
wire the center tap can be omitted and we have 2 independent 2 wire
circuits.

It is true that 6 phase, 12 phase, etc are are derived from 3 phase
systems and provide no net power advantage over 3 phase. 6 phase has
some advantages in compact transmission lines because the interphase
voltage is the same as the voltage to neutral and this allows lower
clearances. 6 and 12 phase rectifier supplies offer better smoothing of
the DC. Other than these advantages -nothing.
Balanced 3 phase does have an advantage over balanced 2 phase (that is,
single phase, center tapped, as we both prefer to call it) in terms of
transmission, transformation, generation, and motors. This advantage has
nothing to do with power waveforms.

A n phase system is nothing more than n single phase systems that are
interconnected in Y or as a polygon (super delta). Certain advantages
accrue but these generally boil down to $ advantages.

What I've called the 3 wire version of 90 degree 2 phase. Two hots and the
neutral. The 5 wire variant needs no neutral current (the 4 wire variant
doesn't even have a neutral), but, of course, uses more copper.

OK 3 wire 90 degree 2 phase- which is not "balanced" in the sense of 0
neutral current- only the 180 degree version can be balanced- and that
balance is the reason that the Edison system is so useful.

 

[[email protected]]

| [email protected] wrote:
|>
|> | phases are 360/2 degrees apart. 3 phase 360/3 degrees apart, 4 phase
|> | 360/4 etc.
|>
|> That would be the normal way of thinking of it. It gets interesting when the
|> number of phases is any even number. For example 6 phase. I have mentioned
|> the concept of 6 phase before and some people get confused. If a 6 phase
|> system with phases labeled A,B,C,D,E,F (going around the circle) with phase
|> angles of 360/6 degrees each, gives you 240 volts between A and D, then why
|> can't a subsystem tapped from just A and D alone be called 2 phase? They are
|> counted as 2 phases.
|>
|>
| That depends on how you look at it- if you bring out only the two
| terminals A,D you have a single voltage between them. It is then
| indistinguishable from a single phase 2 wire supply. With a single
| voltage, phase, as a relative term, becomes a problem. as what do you
| relate this single voltage to?

If you have a neutral or ground or some kind of ground reference, even if
high impedance, then you have 3 points, 2 or 3 vectors, and can determine
an angle. If you don't, all you have is the voltage difference.


| If the 6 phase system is a Y rather than a polygon (super delta) then
| you have a neutral and then you can consider that you have a 2 phase
| system where the voltages Van and Vbn are 180 degrees apart. You then
| have 3 terminals. This is indistinguishable from the center tapped
| single phase system which fits what the Europeans refer to as 2 phase.
| Neither are distinguishable from a 2 wire single phase system if you
| ignore the neutral.

Is it standard in Europe to use "2 phase" to refer to what Americans mostly
use some variation of "Edison style split single phase"?

I don't like to call any AC system based on Edison in any way. Edison did
not design around AC. He did DC. Thus he didn't split his power system in
any way considering angles, because there were no angles. Edison would not
recognize the power system coming into my home. Tesla might.

And Edison is quite far from being my favorite inventor/scientist/engineer.

 

[[email protected]]

| In article <[email protected]>,
|
|> That depends on how you look at it- if you bring out only the two
|> terminals A,D you have a single voltage between them. It is then
|> indistinguishable from a single phase 2 wire supply. With a single
|> voltage, phase, as a relative term, becomes a problem. as what do you
|> relate this single voltage to?
|> If the 6 phase system is a Y rather than a polygon (super delta) then
|> you have a neutral and then you can consider that you have a 2 phase
|> system where the voltages Van and Vbn are 180 degrees apart. You then
|> have 3 terminals. This is indistinguishable from the center tapped
|> single phase system which fits what the Europeans refer to as 2 phase.
|> Neither are distinguishable from a 2 wire single phase system if you
|> ignore the neutral.
|
| I have just come up with a magic box. I connect its to a three-phase
| source. I ask a technician to measure the voltages between pairs of
| wires leaving the output of the box. She comes up with two measurements
| of 120V and one of 170V. Should the Tech be fired?
|
| The box is a Scott T transformer.
|
| What is the point. Once you have two phases, you can build equipment
| that gives you anything you want. Actually, one phase (and retiurn is
| enough, although more complicated.
|
| All this talk is garbage. Just stick to fundamentals!

Fundamnetally, Edison did not contribute to AC.

Fundamentally, you can have a reference terminal, and 2 power terminals with
AC output at some fixed frequency. If you have controls to change their phase
angles, you still have 2 of them, even if you happen to adjust them to exactly
180 degrees apart.

 

[daestrom]

| [email protected] wrote:

Is it standard in Europe to use "2 phase" to refer to what Americans
mostly
use some variation of "Edison style split single phase"?

I don't like to call any AC system based on Edison in any way. Edison did
not design around AC. He did DC. Thus he didn't split his power system
in
any way considering angles, because there were no angles. Edison would
not
recognize the power system coming into my home. Tesla might.

Au contrarie, Edison might look at the three wires, measure 120/120 and 240
and say, "Gee, that's pretty much how I did it except you're using that
'deadly' AC crap!"

daestrom

 

[Don Kelly]

I have just come up with a magic box. I connect its to a three-phase
source. I ask a technician to measure the voltages between pairs of
wires leaving the output of the box. She comes up with two measurements
of 120V and one of 170V. Should the Tech be fired?

Correct <if> you look at the voltages with respect to the T junction-
assuming it is available external to the box-there is no reason for it
to be so. There is another set of terminals so 3 more voltage pairs can
be measured- the 3 phase input. The technician should be fired for not
measuring the voltages between the supply terminals but more importantly
not measuring the <output> voltage as specified. The voltages from the T
junction are not the output. If you look at the <output> terminals,
you will have two sets of voltages in quadrature -2 phase- and the
result will be two equal voltages in quadrature.

 

[Don Kelly]

I'm not talking about the average power. I'm talking about the
instantaneous power over a complete cycle.



Again, I am not talking about average power. I had more in mind a polyphase
AC motor, which consumes a fixed amout of power, no matter what the
instantaneous phase relationship is at any moment in time. It delivers
a fixed power to its load, without vibrations from the power line frequency
under ideal conditions. It also has a rotating field allowing for
automatic start. Contrast with a single phase induction motor, whose
power consumption at any point in time varies with the input waveform.

OK we are now getting down to something I said in error regarding the
instantaneous power in the different cases- I did my math this morning
and OOPS was the result. . Yes, the single phase and 2 phase,180 degree
system which we both prefer to call a 3 wire single phase system will
have a net pulsating power and will not inherently produce a rotating
field while the 3 phase and 2 phase 90 degree systems have constant
instantaneous power and can inherently produce a rotating field.

Here we run into a conflict between two definitions of "balanced"

One definition uses the balanced set of voltages each shifted 360/n
degrees from the adjacent phases so that the sum of phase to neutral
voltages and phase currents are each 0. That is the the neutral current
=0. This is not fully spelled out in Gross, "Power System Analysis" but
is implied in the first chapter which is the only place that he makes a
comparison between alternative transmission schemes. The 180 degree
apart single phase 3 wire system fits this.

On the other hand, Krause and Wasynczuk "Electromechanical Motion
Devices" define the "balanced 2 phase system as you do, equal voltages
in quadrature- as you have done. This is a machines perspective as only
this form produces constant instantaneous power and a single rotating
field.

This just goes to show that an unbalanced polyphase source can be made
to degrade until it becomes almost as bad as a single phase source, yet
there still is something fundamental that happens at 180 degrees and
nowhere else (except 0 degrees). You can still generate a constant
power draw, even if it becomes absurdly difficult, by, for example,
extracting two outputs derived from the sum and the difference between
the two voltages, and scaling them (with transformer turns ratio) - as
long as the phase isn't 180 or 0 degrees. When, for example the angle
is 179 degrees, and the voltage is 100V, the difference voltage is nearly
200V and nearly in phase with the two legs, but the sum voltage is less
than 1% of that, ~1.75 volts, but at about 90 degrees to the first.
You could step it up to almost 100:1, but now we increase the current
100 times, and it's a horribly reactive load, a power factor of near 0.
But it's still possible. Not at exactly 180 degrees, however, since to
get the 90 degree phase you'd have to divide by 0 since the sum is now a
constant 0. But in this case (only) you can use one transformer instead
of two.

Saying that "there is no fundamental change" that happens at this angle
is not true. It's like saying that if you plot the graph y=1/x, there is
no fundamental change that happens at x=0.

It is not as drastic as that. Actually, the magnitude of the double
frequency component will change in a well behaved manner-as the
magnitude of the cosine of the relative phase angle. so it will be 1
at 180 and 0 at 90 degrees while the magnitude of the average power
happily remains at 1 throughout.
Nothing drastic happens at 180 degrees- all that happens is that the
neutral current is 0 (a bonus) and that the pulsating component of the
instantaneous power is at a maximum (not a bonus).

So while the total instantaneous power will have a double frequency
component dependent on the relative phase of the two voltages, the total
average power will be the same at all phase angles between the legs,
corresponding to the sum of the average power in each leg-taken
individually.
I'm not sure what you are trying to do by using the sum and difference
approach (particularly if you are using phasors as it appears when you
talk about 100V, 1.75V at nearly 90 degrees etc as power calculated from
phasors will be the average power, not instantaneous power)
Why bother- just consider what the situation is for different angles
between the legs. No horrible reactive problems or scaling needed.
Surely you are not proposing such an exercise just in order to keep the
total instantaneous power constant- it isn't worth the effort and time
domain, not phasor analysis would be needed.

Now, for a induction motor, certainly the double frequency term is a
nuisance and at the 0 and 180 degree points, there will be no starting
torque and running torque will be pulsating. Hence the desire for a 90
degree shift. Single phase motors are definitely inferior to a polyphase
motor, including a two phase machine- but two phase systems of any
consequence died before either of us saw daylight - some recovered
during the 40's as low power control motors and tachometers (phase fixed
but voltage magnitudes variable).

 

[Don Kelly]

| On 20 Feb 2009 04:13:20 GMT, [email protected] wrote:
|
|>
|>My understanding is that his DC system was 110/220 volts, not 120/240.
|
|
| Ithought it started at 100 and crept up over several years.

It was at 110 volts when Edison started running his DC service in NYC.
I also know 220 volts was being used in Europe by that time. I suspect
he decided to start with that 220 volts, but determined that light bulb
filaments last longer when designed for lower voltages, because they are
thicker and shorter (or maybe just that when he designed them to last
longer, they just used a lower voltage) ... so he decided to split the
system in half to accomodate the light bulb on a lower voltage.

If only he had accepted AC then we might have universally ended up with
all incandescent lights operating at perhaps 12 volts or so, stepped down
near the point of use, with a higher voltage going into the building.

Not likely- have you priced copper? How about a 1500 watt kettle at 12
V, 125A- this would have to be a fixture in that it would be extremely
difficult to move.

 

[Don Kelly]

Correct <if> you look at the voltages with respect to the T junction-
assuming it is available external to the box-there is no reason for it
to be so. There is another set of terminals so 3 more voltage pairs
can be measured- the 3 phase input. The technician should be fired for
not measuring the voltages between the supply terminals but more
importantly not measuring the <output> voltage as specified. The
voltages from the T junction are not the output. If you look at the
<output> terminals, you will have two sets of voltages in quadrature
-2 phase- and the result will be two equal voltages in quadrature.

****************
Apologies- my statements above are arrant nonsense. The only excuse that
I have is that I was distracted by the wind whistling between my ears as
when I went to bed and blocked the wind with a pillow, it became obvious
that I blew it.

 

[[email protected]]

| [email protected] wrote:
|> | On 20 Feb 2009 04:13:20 GMT, [email protected] wrote:
|> |
|> |>
|> |>My understanding is that his DC system was 110/220 volts, not 120/240.
|> |
|> |
|> | Ithought it started at 100 and crept up over several years.
|>
|> It was at 110 volts when Edison started running his DC service in NYC.
|> I also know 220 volts was being used in Europe by that time. I suspect
|> he decided to start with that 220 volts, but determined that light bulb
|> filaments last longer when designed for lower voltages, because they are
|> thicker and shorter (or maybe just that when he designed them to last
|> longer, they just used a lower voltage) ... so he decided to split the
|> system in half to accomodate the light bulb on a lower voltage.
|>
|> If only he had accepted AC then we might have universally ended up with
|> all incandescent lights operating at perhaps 12 volts or so, stepped down
|> near the point of use, with a higher voltage going into the building.
|>
|>
| Not likely- have you priced copper? How about a 1500 watt kettle at 12
| V, 125A- this would have to be a fixture in that it would be extremely
| difficult to move.

And how does the price of copper have anything to do with stepping down the
voltage AT (or near, like within a couple feet) THE POINT OF USE, such as is
done now for a few lighting systems.

IMHO, had Edison accepted AC, he would have realized he could design filaments
for his incandescent lights at an even lower voltage than the 110 volts he got
by splitting the 220 volt system in half. His electric light would be even
more reliable at lower voltages like 6 to 16 volts or so. Of course he knew
that he could not practically distribute power at these low voltages due to
the higher current and the greater impact of voltage drop. What he could have
done with AC is adopt the notion of having a small transformer at each light,
run the filament at 10 volts, and distribute power into buildings at 440 volts
(maybe with a split 220/440 system). With the light sockets only having 10
volts, instead of the voltage in use to distribute electricity within (and on
his initial scale, also between) each building, he could have used a higher
distribution voltage safely.

What I'm saying is that if he had done all this, low voltage incandescent
lighting would likely be the universal norm through the 20th century, and
we would also more likely have a higher line voltage for power the many other
things we hook up to electricity since then. We might have ended up with
something like 220/440 coming in each home, and stepping it down to 10 volts
at each light.

Edison may have even accepted the idea of three phase. The man was more
interested in the money from inventions rather than the inventions, per se.
So if he could have been convinced of the money in powering motors from his
electrical service, he might have used three phase, as well.

 

[[email protected]]

|
| |> | [email protected] wrote:
| <snip>
|> Is it standard in Europe to use "2 phase" to refer to what Americans
|> mostly
|> use some variation of "Edison style split single phase"?
|>
|> I don't like to call any AC system based on Edison in any way. Edison did
|> not design around AC. He did DC. Thus he didn't split his power system
|> in
|> any way considering angles, because there were no angles. Edison would
|> not
|> recognize the power system coming into my home. Tesla might.
|
| Au contrarie, Edison might look at the three wires, measure 120/120 and 240
| and say, "Gee, that's pretty much how I did it except you're using that
| 'deadly' AC crap!"

And, of course, that was Edison's downfall from being a big supplier of electric
power to the country. But had he accepted AC back in those days, I believe it
would have had much more influence on what we have today as electrical systems
than anything we could possibly do today. If he had stepped AC down to 10 volts
at the light socket, he would have been able to make electricity safer (because
the light socket was the most dangerous part, being right up near where people
worked), but also made his light bulbs more reliable (lower voltage means a
thicker filament). His goal wasn't to sell light bulbs in greater quantity.
His goal was to sell electric service as a replacement for gas lighting.

 

[daestrom]

|
| |> | [email protected] wrote:
| <snip>
|> Is it standard in Europe to use "2 phase" to refer to what Americans
|> mostly
|> use some variation of "Edison style split single phase"?
|>
|> I don't like to call any AC system based on Edison in any way. Edison
did
|> not design around AC. He did DC. Thus he didn't split his power
system
|> in
|> any way considering angles, because there were no angles. Edison would
|> not
|> recognize the power system coming into my home. Tesla might.
|
| Au contrarie, Edison might look at the three wires, measure 120/120 and
240
| and say, "Gee, that's pretty much how I did it except you're using that
| 'deadly' AC crap!"

And, of course, that was Edison's downfall from being a big supplier of
electric
power to the country. But had he accepted AC back in those days, I
believe it
would have had much more influence on what we have today as electrical
systems
than anything we could possibly do today. If he had stepped AC down to 10
volts
at the light socket, he would have been able to make electricity safer
(because
the light socket was the most dangerous part, being right up near where
people
worked), but also made his light bulbs more reliable (lower voltage means
a
thicker filament). His goal wasn't to sell light bulbs in greater
quantity.
His goal was to sell electric service as a replacement for gas lighting.

Ah he was smarter than that. Let's see, you want to put a small transformer
in every light fixture so that he won't sell as many light bulbs. General
Electric (which at one time was Edison's company IIRC), sold lightbulbs by
the millions.

Considering that few people are conversant with total cost of operation,
they would have looked at Edison's more expensive light sockets and opted
for someone else's product line.

daestrom

 

[Don Kelly]

| [email protected] wrote:
|> | On 20 Feb 2009 04:13:20 GMT, [email protected] wrote:
|> |
|> |>
|> |>My understanding is that his DC system was 110/220 volts, not 120/240.
|> |
|> |
|> | Ithought it started at 100 and crept up over several years.
|>
|> It was at 110 volts when Edison started running his DC service in NYC.
|> I also know 220 volts was being used in Europe by that time. I suspect
|> he decided to start with that 220 volts, but determined that light bulb
|> filaments last longer when designed for lower voltages, because they are
|> thicker and shorter (or maybe just that when he designed them to last
|> longer, they just used a lower voltage) ... so he decided to split the
|> system in half to accomodate the light bulb on a lower voltage.
|>
|> If only he had accepted AC then we might have universally ended up with
|> all incandescent lights operating at perhaps 12 volts or so, stepped down
|> near the point of use, with a higher voltage going into the building.
|>
|>
| Not likely- have you priced copper? How about a 1500 watt kettle at 12
| V, 125A- this would have to be a fixture in that it would be extremely
| difficult to move.

And how does the price of copper have anything to do with stepping down the
voltage AT (or near, like within a couple feet) THE POINT OF USE, such as is
done now for a few lighting systems.

nothing at all except that you still have the higher voltage circuits to
nearly the point of use and then drop to the lower voltage-In most
situations (other than the low voltage and relatively low and fixed
power applications that you cite, it would be necessary, for every
outlet, to provide the capacity for loads of the order of those
presently used.
The reason for the present compromise voltage levels is an economic one
and the economics involved hold true even now. There is also the problem
of a user pulling the plug on a 12 V 125A kettle. Even with AC, that
doesn't fill me with joy. Sure you can get around this problem at a
price, but "while you can make something foolproof, you can't make it
damnfool proof "(quote from a long gone prof- Dr Harle)

IMHO, had Edison accepted AC, he would have realized he could design filaments
for his incandescent lights at an even lower voltage than the 110 volts he got
by splitting the 220 volt system in half. His electric light would be even
more reliable at lower voltages like 6 to 16 volts or so. Of course he knew
that he could not practically distribute power at these low voltages due to
the higher current and the greater impact of voltage drop. What he could have
done with AC is adopt the notion of having a small transformer at each light,
run the filament at 10 volts, and distribute power into buildings at 440 volts
(maybe with a split 220/440 system). With the light sockets only having 10
volts, instead of the voltage in use to distribute electricity within (and on
his initial scale, also between) each building, he could have used a higher
distribution voltage safely.

What I'm saying is that if he had done all this, low voltage incandescent
lighting would likely be the universal norm through the 20th century, and
we would also more likely have a higher line voltage for power the many other
things we hook up to electricity since then. We might have ended up with
something like 220/440 coming in each home, and stepping it down to 10 volts
at each light.

Edison may have even accepted the idea of three phase. The man was more
interested in the money from inventions rather than the inventions, per se.
So if he could have been convinced of the money in powering motors from his
electrical service, he might have used three phase, as well.

"Might have" is very questionable- the present voltage levels are an
imperfect compromise between a wide range of initial systems- that
attempted to optimize a number of diverse factors. You can't apply
hindsight, based on today's technical capability, upon our
predecessors. The technology of his day was not up to it.Look at the
construction of his generators, transformers of the period, insulation
materials, etc. I have run an induction motor which was designed and
built somewhat later -say 1910 and this was a lovely machine -
handcrafted to a great extent and benefiting from better technology than
any at Edison's beck and call. While it was built to last, it was much
larger and less efficient than today's equivalent. A 1KVA transformer in
those days was a beast, in more ways than one, compared to its modern
equivalent- definitely not something that you want to try to install in
a typical wall-and definitely more of a fire hazard. Edison wouldn't
even have considered it -he wasn't economically astute.

IMHO, Edison has been given credit for too much. He was not the
originator of the modern power distribution system as often claimed.
Tesla, Gaullard & Gibbs, Westinghouse had much more to do with this.
Edison was restricted to local areas and made no move to try and get
around this.
As far as many other innovations of his time, credit must be given to
Brush, Elihu Thompson and others. Thompson was a more efficient
inventor than Edison in that he thought things out and then tried them
out -something that Edison wasn't noted for.

 

[[email protected]]

|
| |> |
|> | |> |> | [email protected] wrote:
|> | <snip>
|> |> Is it standard in Europe to use "2 phase" to refer to what Americans
|> |> mostly
|> |> use some variation of "Edison style split single phase"?
|> |>
|> |> I don't like to call any AC system based on Edison in any way. Edison
|> did
|> |> not design around AC. He did DC. Thus he didn't split his power
|> system
|> |> in
|> |> any way considering angles, because there were no angles. Edison would
|> |> not
|> |> recognize the power system coming into my home. Tesla might.
|> |
|> | Au contrarie, Edison might look at the three wires, measure 120/120 and
|> 240
|> | and say, "Gee, that's pretty much how I did it except you're using that
|> | 'deadly' AC crap!"
|>
|> And, of course, that was Edison's downfall from being a big supplier of
|> electric
|> power to the country. But had he accepted AC back in those days, I
|> believe it
|> would have had much more influence on what we have today as electrical
|> systems
|> than anything we could possibly do today. If he had stepped AC down to 10
|> volts
|> at the light socket, he would have been able to make electricity safer
|> (because
|> the light socket was the most dangerous part, being right up near where
|> people
|> worked), but also made his light bulbs more reliable (lower voltage means
|> a
|> thicker filament). His goal wasn't to sell light bulbs in greater
|> quantity.
|> His goal was to sell electric service as a replacement for gas lighting.
|>
|
| Ah he was smarter than that. Let's see, you want to put a small transformer
| in every light fixture so that he won't sell as many light bulbs. General
| Electric (which at one time was Edison's company IIRC), sold lightbulbs by
| the millions.

Edison was not making light bulbs to sell light bulbs. If that were the case,
he wouldn't have done what it did to actually try to extend the life of them.
Remember, he did not invent the light bulb. He just improved on it. Instead,
he was trying to create a greater demand for electricity than existed for a
few motors here and there at the time.


| Considering that few people are conversant with total cost of operation,
| they would have looked at Edison's more expensive light sockets and opted
| for someone else's product line.

Either way, the business model was on creating a demand for electricity and
selling an incrementally priced service. He would not have the market locked
up on light bulbs for very long. His goal was the electric service business
which would be a monopoly where it was deployed.

 

[[email protected]]

|> And how does the price of copper have anything to do with stepping down the
|> voltage AT (or near, like within a couple feet) THE POINT OF USE, such as is
|> done now for a few lighting systems.
|>
| nothing at all except that you still have the higher voltage circuits to
| nearly the point of use and then drop to the lower voltage-In most
| situations (other than the low voltage and relatively low and fixed
| power applications that you cite, it would be necessary, for every
| outlet, to provide the capacity for loads of the order of those
| presently used.

We don't have a problem with high currents on low voltage lighting today for
the 12 volt level. Why would Edison have had that problem.


| The reason for the present compromise voltage levels is an economic one
| and the economics involved hold true even now. There is also the problem
| of a user pulling the plug on a 12 V 125A kettle. Even with AC, that
| doesn't fill me with joy. Sure you can get around this problem at a
| price, but "while you can make something foolproof, you can't make it
| damnfool proof "(quote from a long gone prof- Dr Harle)

I'm not suggesting 12 volts for a 1500 watt kettle. That should run on
the line voltage using a safely designed plug that makes it hard to touch
the contacts. The light bulb socket was where people were at great risk
to get an electric shock.

Suppose Edison accepted AC, distributed electricity with a 220/440 volt
system, used a shrouded Europlug for line voltage connections, and used
a transformer to step the voltage down to 10 or 20 volts for each light.
The kettle could be plugged into 220 and draw 6.8 amps. The light fixture
would be a box with a small transformer in it, supplying 20 volts to a 40
watt light bulb. That would be 2 amps in the bulb socket, but only 0.2
amps on the 220 volt circuit supplying the transformer.

I don't see where you are getting the notion of running the kettle on low
voltage.


| "Might have" is very questionable- the present voltage levels are an
| imperfect compromise between a wide range of initial systems- that
| attempted to optimize a number of diverse factors. You can't apply
| hindsight, based on today's technical capability, upon our
| predecessors. The technology of his day was not up to it.Look at the
| construction of his generators, transformers of the period, insulation
| materials, etc. I have run an induction motor which was designed and
| built somewhat later -say 1910 and this was a lovely machine -
| handcrafted to a great extent and benefiting from better technology than
| any at Edison's beck and call. While it was built to last, it was much
| larger and less efficient than today's equivalent. A 1KVA transformer in
| those days was a beast, in more ways than one, compared to its modern
| equivalent- definitely not something that you want to try to install in
| a typical wall-and definitely more of a fire hazard. Edison wouldn't
| even have considered it -he wasn't economically astute.

I am applying the _hypothetical_ scenario of Edison accepting alternating
current as something that could be made safe enough. I'm not convinved
that he believed AC to be particularly more dangerous. Instead, he was
trying to push the idea of AC being dangerous because if AC were adopted
as a standard, his investment in DC generation for Lower Manhattan would
be lost.

And he could have just become more stubborn due to his dislike of Tesla.

Somewhere along the way he believed DC to be better. I don't know what
all the reasons were. Perhaps he wanted to sell electricity to users of
DC motors, too.

I'm still convinced that if someone "saw the light" about the meeting of a
more reliable light filament for low voltage and the practicality of AC to
deliver that low voltage without cost of delivering it at that voltage,
history might have been different. They had the technology to do it back
then. Tesla missed it (he focused on large lights for illuminating big
outdoor spaces and apparently missed understanding the benefit of lower
voltage on small room and work area lights). Edison missed it (because
of his obsession with DC) even though he understood lower voltage worked
better with filaments.


| IMHO, Edison has been given credit for too much. He was not the
| originator of the modern power distribution system as often claimed.
| Tesla, Gaullard & Gibbs, Westinghouse had much more to do with this.
| Edison was restricted to local areas and made no move to try and get
| around this.

Indeed, the DC technology of the day limited him to that. We might be able
to make a semi-practical DC-only wider area electric service with technology
we have today in 2009. But Mr. Edison didn't have this option. And today,
there's no point because such a DC system would provide no benefit over what
we already have in place, and would face an immense conversion cost.

AC is the right choice for us. But I believe line voltage incandescent
lighting never was a good choice for anything short of 600 to 1000 watts
per bulb. Low voltage should have been used for incandescent lighting.
Then the requirements of incandescent bulb filaments would NOT have been
a factor, or at least as big a factor, in the compromises that determined
the voltages we use. I believe the choice of 110 volts would not have
been necessary with the lighting of the day done on stepped down voltage,
which could have been done from 220 or even 440.


| As far as many other innovations of his time, credit must be given to
| Brush, Elihu Thompson and others. Thompson was a more efficient
| inventor than Edison in that he thought things out and then tried them
| out -something that Edison wasn't noted for.

Agreed. Edison was more a businessman who has some inventor skills and could
do a fair amount of technical thinking. Bill Gates didn't invent computer
software, or operating systems, or even a Graphical User Interface. He was a
business man who saw a potential market that, when he was starting, had to be
made. Gates just didn't narrow his plans based on what he himself could make.

Brush and Thomson (no "p") were genuine inventors.

 

[daestrom]

| Considering that few people are conversant with total cost of operation,
| they would have looked at Edison's more expensive light sockets and
opted
| for someone else's product line.

Either way, the business model was on creating a demand for electricity
and
selling an incrementally priced service. He would not have the market
locked
up on light bulbs for very long. His goal was the electric service
business
which would be a monopoly where it was deployed.

I disagree. ISTR one of his 'demons' driving him to produce a *practical*
electric lamp was that he was concerned over the fire hazards of gas/oil
lamps. The 'Edison Electric Lamp' was clean and much safer. My father had
an advertising poster from that era that boasted no need to strike a match,
this room was equiped with the new, cleaner and safer Edison Electric Lamp.

daestrom

 

[[email protected]]

|
| | <snip>
|> | Considering that few people are conversant with total cost of operation,
|> | they would have looked at Edison's more expensive light sockets and
|> opted
|> | for someone else's product line.
|>
|> Either way, the business model was on creating a demand for electricity
|> and
|> selling an incrementally priced service. He would not have the market
|> locked
|> up on light bulbs for very long. His goal was the electric service
|> business
|> which would be a monopoly where it was deployed.
|
| I disagree. ISTR one of his 'demons' driving him to produce a *practical*
| electric lamp was that he was concerned over the fire hazards of gas/oil
| lamps. The 'Edison Electric Lamp' was clean and much safer. My father had
| an advertising poster from that era that boasted no need to strike a match,
| this room was equiped with the new, cleaner and safer Edison Electric Lamp.

To some degree he was concerned over the gas/oil hazard. But he also knew
the public was concerned over it and was merely taking advantage of it with
a solution that was indeed safer. It's not any different than any other
business recognizing a public concern and providing a solution because they
can see a market in something safer. But this would be the same whether DC
or AC power was used. The big issue was why Edison wanted to stay with DC.
Did he genuinely believe AC was more dangerous, or was he just protecting his
investment in DC and marketing AC as dangerous.