just call it 2 phase

| wrote: | |> |> And these were plugged into Edison's DC system? | | That would do it. Did you ever work on one of those radios?
I don't know if I have. I never had any DC of that voltage to plug any radios into. I did have some old radios that ran on 110VAC or so, but I only ever tried them on AC.
| As an aside, IIRC, the dc motors were switched on and of by the | operators. Where only ac was available,the motors ran continuously. The | operator operated a clutch that connected mechanical power to the sewing | machine.
Maybe DC would heat them up more?
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snipped-for-privacy@ipal.net wrote:

No. They were plugged into the cigarette lighter of the flying saucers at Area 51. If you are going to continue to post nonsense, I might as well, too. :(
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On Fri, 27 Mar 2009 15:42:42 -0400 Michael A. Terrell
| | snipped-for-privacy@ipal.net wrote: |> |> On Wed, 25 Mar 2009 07:57:52 -0400 Michael A. Terrell
|> |> | A lot of transformerless tube radios were sold as AC/DC, and wouldn't |> | have worked if it was a Phil claims. You just had to make sure the |> | power plug was inserted the right way, or you got no B+ for the tubes. |> |> And these were plugged into Edison's DC system? | | | No. They were plugged into the cigarette lighter of the flying | saucers at Area 51. If you are going to continue to post nonsense, I | might as well, too. :(
I asked a question. Obviously you never provide useful answers.
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snipped-for-privacy@ipal.net wrote:

You never post any useful questions. You just post crap, or try to play troll, but you aren't capable of even doing that properly. WTH would they have built AC/DC radios if they couldn't be operated on Edison's DC generator designs? You can't be that stupid? Or can you?
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On Sun, 29 Mar 2009 04:13:27 -0400 Michael A. Terrell
| | snipped-for-privacy@ipal.net wrote: |> |> On Fri, 27 Mar 2009 15:42:42 -0400 Michael A. Terrell
|> |
|> |> |> |> On Wed, 25 Mar 2009 07:57:52 -0400 Michael A. Terrell
|> |> |> |> | A lot of transformerless tube radios were sold as AC/DC, and wouldn't |> |> | have worked if it was a Phil claims. You just had to make sure the |> |> | power plug was inserted the right way, or you got no B+ for the tubes. |> |> |> |> And these were plugged into Edison's DC system? |> | |> | |> | No. They were plugged into the cigarette lighter of the flying |> | saucers at Area 51. If you are going to continue to post nonsense, I |> | might as well, too. :( |> |> I asked a question. Obviously you never provide useful answers. | | | You never post any useful questions. You just post crap, or try to | play troll, but you aren't capable of even doing that properly. WTH | would they have built AC/DC radios if they couldn't be operated on | Edison's DC generator designs? You can't be that stupid? Or can you?
Questions are not something that has utility, except for people that want to know the answers. You do not need to perceive any utility in questions that I or anyone else asks. The utility of a questions does depend on the answers is gets.
AC/DC radios could be built to operate on AC or batteries. You cannot assume ever AC/DC radio ever built was intended to operate on the kind of DC system Edison ran. It might be that they didn't engage any filtering at all for DC.
If you had simply answered the question, the conversation would move forward. Instead, you clearly have the intent to always derail conversations. Should I assume malice on your part? Or maybe just incompetence in reading English?
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wrote:

The history of development of these radios is unknown to me at present. Whoever came up with the idea for transformerless ac radios must have realized that it would work about as well on Edison's dc system.
As a kid, I remember getting an RCA tube manual that had a lot of information on popular tubes. It cost about 25. The manual included many circuits for different kinds of equipment. It included an ac/dc radio of the kind being discussed.
At that time, RCA owned most of the patents transferred to them from the likes of GE,Westinghouse, ATT, etc. It behooved RCA to come up with designs that it would license to anyone capable of paying. At that time, I did not understand the concept of licensing--it still is a mystery to me.
Among other things, there were radio articles in Popular Science. One was on how to build an ac/dc radio.
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snipped-for-privacy@ipal.net wrote:

Stupid questions deserve stupid answers, when the one asking the questions is trolling.

That's it. Another fantasy, instead of doing any research.
http://www.pmillett.com/technical_books_online.htm is a wealth of early tube circuit data, including the Radiotron Designers handbook, an multiple receiving tube manuals with circuits of AA5, AC/DC radios. I know you are too arrogant and ignorant to download and read any of them, but the proof is out there.
As far as no filtering on a DC powered radio? Obviously you have never designed or repaired a radio. If there is no filtering on the DC rail, any line noise will blast through, the AVC won't work, and the radio will motorboat. Of course you will deny this, but everyone knows you are just a ham radio operator, not a tech, or an engineer.

ADmit it, Phil. You are just another lame brain troll. Any malice is on your end, in an attempt to cover your tracks on subjects you don't know.
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snipped-for-privacy@ipal.net wrote:

Edison's machines were true DC machines. Some earlier machines were "Gramme Ring" machines which could have given you this impression (falsely). As far as I can see from pictures, his machines were drum armature 2 pole machines with a conventional commutator (which is a synchronous switch). Note that a commutator, properly used, switches the current only in the individual coils under the brushes, shorting the coils (2 in his case) on the neutral axis-at a time when the individual coil voltage changes polarity. During the time that the brush contact moves from one side of the coil to the other, shorting the coil in the interim, the voltage in that coil would be nearly 0. The total voltage would have little ripple as the rest of the coils would be producing normal voltage so the total voltage certainly did not go to 0 or near 0. Brush width and material was a problem until it was discovered (by Brush or Thompson- I can't recall which) that carbon was ideal. Modern machines are designed to compensate for armature reaction which shifts the neutral axis and causes arcing. In Edison's day this compensation was done manually. In operation, except for considerable refinements in design, Edison's machines were essentially the same as modern DC machines.
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Not when you look at the delivered power to an ideal resistive load.

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, 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)
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.
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.

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.
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On Thu, 19 Feb 2009 19:28:38 +0000 (UTC) Michael Moroney
| 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.
There is the distinction between an unbalanced polyphase system and a balanced polyphase system. The balanced polyphase system (3 or more phases) delivers the uniform power waveform. As long as the system is balanced, this works.
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snipped-for-privacy@ipal.net writes:

90 degree 2 phase delivers a balanced power waveform. A sine wave shifted 90 degrees is a cosine wave, and you may remember from math sin^2(x)+cos^2(x)=1 for any x.
90 degree 2 phase (the 3 wire version, anyway) does not, however, have a zero neutral current when balanced.
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On Fri, 20 Feb 2009 20:05:18 +0000 (UTC) Michael Moroney
| snipped-for-privacy@ipal.net writes: | |>On Thu, 19 Feb 2009 19:28:38 +0000 (UTC) Michael Moroney
| |>| 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. | |>There is the distinction between an unbalanced polyphase system and a balanced |>polyphase system. The balanced polyphase system (3 or more phases) delivers |>the uniform power waveform. As long as the system is balanced, this works. | | 90 degree 2 phase delivers a balanced power waveform. A sine wave shifted | 90 degrees is a cosine wave, and you may remember from math | sin^2(x)+cos^2(x)=1 for any x.
You're right. This will work down to 2 phases when the angles are correct. Ironically, the mathematics is identical to 4 phases, or generalized is identical to 2x phases for any N phase system. And that means the 2 phase 180 degree system (also known as Edison split) is the equivalent in terms of power waveform as 1 phase.
| 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.
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snipped-for-privacy@ipal.net writes:

Yes. That's why everything is 3 phase today.
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On Sun, 22 Feb 2009 01:30:25 +0000 (UTC) Michael Moroney
| snipped-for-privacy@ipal.net 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.
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Michael Moroney wrote:

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

----- 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.

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..

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.

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.

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.
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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.

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.
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Michael Moroney wrote:

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.

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).
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Most stepper motors are actually two-phase devices. They are often driven by two square waves with a 90 degree phase shift, but they can also be driven by sine waves to give a much smoother rotation.
    Dave
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|>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). | | Most stepper motors are actually two-phase devices. They are often | driven by two square waves with a 90 degree phase shift, but they can | also be driven by sine waves to give a much smoother rotation.
Controlled motors can be done in a lot of ways. A couple years ago I did a forensic disassembly of a VCR that was hit by lightning, and notice the head motor on it was 12 pole. This certainly wasn't a power frequency driven motor.
For very basic motors, with little or no control, the practical choices have been made already.
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Dave Martindale wrote:

You are right. I am showing my age in referring to 2 phase "variable voltage on one phase" 2 phase machines-which predated steppers-using sinusoidal excitation. In the same era, 3 phase devices for remote positioning (forget the name) were used. In that era, the modern digital electronic control was not available or was too bloody clumsy prior to transistors and integrated circuits. Since then both 3 phase and 2 phase steppers have been built and used. From your comments, it appears that the pros and cons of 3 vs 2 phase steppers have come down in favour of 2 phase. For sinusoidal excitation- they are equivalent except for a 3/2 factor in the torque/current relationship.
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