just call it 2 phase

wrote: <snip>


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
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| wrote: | <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.
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daestrom wrote:

There's no reason each socket would have needed a transformer.
Edison was a smart guy, but he was rather bull-headed. I've read many books about him over the years, as I've long admired him as well as others such as Tesla and Westinghouse. Edison was dead-set convinced that his DC system was superior, safer, and the only way to go, and he was unable to see it any other way. It was more about his stubbornness than any true technical or market advantage. The attitude is still everywhere, look at all the people who are fiercely loyal to a particular car manufacture or computer operating system. They will go to great lengths to push the superiority of their chosen one while insisting that everything else is worthless junk, regardless of the actual merits of one over the other. It's more a religious argument than anything else.
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On Tue, 24 Mar 2009 13:23:51 -0700, James Sweet

Bad move. More current causes fires, or makes them more of a problem in the home. Fires are a bigger issue than electrical shock ever was.
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On Tue, 24 Mar 2009 17:18:08 -0700 StickThatInYourPipeAndSmokeIt
| On Tue, 24 Mar 2009 13:23:51 -0700, James Sweet
| |> 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), | | | Bad move. More current causes fires, or makes them more of a problem | in the home. Fires are a bigger issue than electrical shock ever was.
For long runs of wiring, yes, more current increases risk. Stepping the voltage down right at the point of utlization is just not that kind of risk. Millions of low voltage lighting systems in use today would have to be ripped out if this were a problem. Fires due to overloaded circuits are a continuing problem even at line voltage. That's one reason my kitchen plans include 6 outlets (4x 5-15 on 2x 20 amp circuits, 1x 5-20 on its own dedicated circuit, and 1x 6-20 also on a dedicated circuit) at each point where outlets will be. Plenty of outlets means none of those triple tap things. I saw one catch fire when I was young. It had been pulled part way out of the wall outlet due to the weight of the cords plugged into it.
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James Sweet wrote:

In Edison's case, it was a combination of hard headed preservation of his income source (as Daestrom indicates) and the bull-headedness that you indicate. While he pushed the "safety factor" (and it is true that human response to 60Hz is greater than to DC and higher frequencies- but Edison didn't know that!) despite lack of evidence to the contrary (I would rather break 100A AC at any voltage level than for DC at the same or lower voltage level for DC).
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| In Edison's case, it was a combination of hard headed preservation of | his income source (as Daestrom indicates) and the bull-headedness that | you indicate. While he pushed the "safety factor" (and it is true that | human response to 60Hz is greater than to DC and higher frequencies- but | Edison didn't know that!) despite lack of evidence to the contrary (I | would rather break 100A AC at any voltage level than for DC at the same | or lower voltage level for DC).
As I understand it, Edison's DC system was actually pulsed DC from generators with brush contacts switching polarity. Or at least that's the illustrations I have seen. Perhaps he paralleled then at different locked phases to avoid the zero voltage point? If it was truly pulsed and went to zero volts, then shouldn't it have been as easy to break fault current as AC?
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wrote:

I presume, until I hear otherwise, that the generators used by Edison were fairly similar to modern dc generators except for refinements and bells and whistles.
Coils rotating in and cutting the magnetic field. Each is connected in series with adjacent coils as well as to commutator segments. Each coil generates ac that gets rectified at the commutator. The brushes contact the commutator at segments that have small potential differences between adjacent segments. That is because the attached coils happen to be moving mostly along the magnetic field.
Except for some commutator ripple as the brush shorts out adjacent pairs as it moves along the segments, the output is dc all the way. There is not series of pulses.
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Salmon Egg wrote:

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.
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Even if the dc was in pulses, the radio would work. When plugged in the right way, the current would still flow through the rectifier tube and be filtered by the same filter used for ac operation.
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Salmon Egg wrote:

The arcing commutator would generate so much hash that all you would get would be a loud buzz. Any time the brush loses contact with the armature, it arcs.
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Michael A. Terrell wrote:

I had a portable radio with a hand crank generator. The generator is nothing more than an ordinary Mabuchi DC motor as you'd find in motorized toys. Spin the motor and you get something resembling DC out which is sufficient to charge a small NiCd cell as well as power the radio even if the cell is completely dead. A generator might not provide absolutely clean pure DC but I'm pretty sure they could have made it work. Cars used generators up until at least the 1960s, they made radios work in those too.
This would all be easy enough to test. Take a mains voltage permanent magnet motor out of something like a string trimmer (weed eater) and spin it with another motor to get around 110V out of it, then connect that to a transformerless radio, lots of those around still. Or heck, just scope the output of a DC toy motor being spun by another motor.
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wrote:

Radios in cars has absolutely nothing to do with this discussion.
The battery in cars is a very low impedance and would hide any "Pulsing" in the output of the generator.
John G.
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John G. wrote:

They have plenty to do with this discussion. The battery is low impedance and does tend to "hide" pulsing just like the B+ filter cap in the radio. As I mentioned, the hand crank radio would operate fine, even when the battery was old and completely worn out to the point that it would no longer take a charge. Anyone is welcome to try this, I see lots of speculation but no hands on experiments here aside from my own from a long time ago. Speaking of old car radios, most of them used a mechanical vibrator to generate the B+ for the plates, talk about hash, the crudest brushed generator would have a cleaner output than one of those still, with shielding and noise filtering, they worked. Additionally, if homes were fed by pulsed DC mains, they could be used to maintain the charge on a bank of batteries similar to the old 32V rural power systems in which batteries were charged by windmills and/or gasoline generators.
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James Sweet wrote:

If homes were still fed with DC, the generators would have to be a couple miles from your home. Also, it doesn't have to pulse to charge a battery.
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Michael A. Terrell wrote:

That wasn't my point. I was just saying that *if* for some reason AC had not succeeded and we still had DC generators powering our homes, radios could still be made to work directly from the generator, even generators build with mid 1800s technology.
I didn't mean to imply that batteries need a pulsed voltage to charge, but simply that hypothetically if design constraints of the generator caused the output to be pulsed, it could still be used to charge batteries and power devices.
In both cases I was simply countering arguments from someone else that this wouldn't work.
Funny thing is with modern technology, DC power distribution would actually have some advantages, though in a residential situation the disadvantages of dealing with high voltage service and large DC-DC or AC converters would far outweigh the advantages, but it could be done. They use it in some long distance transmission lines afterall.
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On Wed, 25 Mar 2009 18:53:08 -0700, James Sweet

It is actually becoming the preference.
We could make a system for residential DC service with the batteries out at streetside. That is a chemical and environmental mess though.
Until battery technology takes a few steps forward or until solar cell technology gets so good that we care less about battery bulk, we will be in an AC fed, AC consuming world. Make for easy conversion, but a magnetically noisy environment.
DC makes for instant 'kill-n-cook' situations though. You really do fry.
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James Sweet wrote:

Sure, but do you want a 500 KV DC line directly to your home? ;-)
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On Wed, 25 Mar 2009 23:05:47 -0400 Michael A. Terrell
| Sure, but do you want a 500 KV DC line directly to your home? ;-)
Does anyone have a 500 kV AC line directly to their home? No.
OTOH, 220VDC would bother me more than 480VAC.
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wrote:

Why? Switching could be more of a problem with no zero crossings.
I have a 2400VAC line running along the property boundary line. I suppose it would be feasible to have a dc to dc converter on poles to distribute at the 110VDC level, but I do not expect that in my lifetime. I do not think that I would want it. You might just as well have rectifiers and switching supplies in the individual devices. That is how all of my personal computers do it.
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