just call it 2 phase

[James Sweet]

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.

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.

 

[James Sweet]

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.

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.

 

[StickThatInYourPipeAndSmokeIt]

but it could be done. They
use it in some long distance transmission lines afterall.

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.

 

[Don Kelly]

| 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?

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.

 

[Don Kelly]

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.

By the time the "mains powered" radios came along, the supply was AC. In
addition, while an arcing commutator produces hash, it produces more
important problems in large DC machines and the design of the
commutation system as well as proper maintainance of the commutator
surface eliminates the arcing.
Small motors such as used in drills do arc because a) nobody maintains
the commutator until the arcing becomes a problem, and b) compensation
for armature reaction is not provided.

 

[Don Kelly]

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.

Sure DC transmission has its advantages- at high voltages for long
distances or for underwater or underground cables or for asynchronous
connections between systems. All point to point rather than grid systems
where specific technical requirements are needed or the distance is long
enough that the savings in transmission costs exceed the costs of the
end equipment. For mid level and distribution, it has serious
disadvantages(no current zeros).- AC offers great advantages in
switching and flexibility of networks and the optimization of voltage
levels for the task at hand with relatively cheap and efficient
transformers.

 

[James Sweet]

Some areas still had DC power well into the '60s and even early
'70s. A friend of mine in the Army told me what his dad had to go
through to get AC for the new elevator in his building near Chicago,
around 1970. The elevator company refused to repair the old DC model,
and only installed new AC powered elevators. People in those areas used
the transformerless radios on the DC power lines, and wouldn't notice
the switch to AC, as long as the usual two electrolytics following the
rectifier were still good.

I read somewhere recently that the last DC service to a building in New
York I believe it was, was shut off sometime in the 1990s. I had no idea
it lasted so long.

Somewhere there is a website with pictures of some of the gigantic
rotary converters used to convert 25Hz AC to DC to drive subway trains.
Some of these were still operational at least up to a few years ago.
I've seen relatively recent pictures of polyphase mercury arc rectifiers
still in operation doing the same job.

 

[[email protected]]

| 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?

 

[[email protected]]

| 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.

And a filter that can remove 60 Hz (or whatever slow rate was in use back in
Edisn's day) could not clean up some modulated noise band at higher freqs?

 

[[email protected]]

| 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.

If using Edison's 220/110VDC split system, even a couple miles would be way
too far. Today would could do transmission, distribution, service, and
utilization, and different DC voltages and keep it DC all the way. It would
still not be as cheap as AC, but it is possible to do.

 

[[email protected]]

| 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.

 

[[email protected]]

| Some areas still had DC power well into the '60s and even early
| '70s. A friend of mine in the Army told me what his dad had to go
| through to get AC for the new elevator in his building near Chicago,
| around 1970. The elevator company refused to repair the old DC model,
| and only installed new AC powered elevators. People in those areas used
| the transformerless radios on the DC power lines, and wouldn't notice
| the switch to AC, as long as the usual two electrolytics following the
| rectifier were still good.

Some parts of West Virginia had 25 Hz into the late 1950's (my grandfather
worked on those). It was there for powering coal mine equipment, but many
businesses and homes were connected, as well.

 

[James Sweet]

Yes, some of them. Edison's system did not vanish overnight, fragments
of it lasted well into the era of the transformerless AC/DC radio. As
mentioned in a previous post, there were buildings in part of NY that
were still supplied with DC until just a few years ago. One of the
advertised features of these radios is that they could be run on either
AC or DC current which was not the case with the safer and more
expensive transformer sets before them.

Useless but related trivia, the band AC/DC got their name from the label
on the back of just such a radio.

 

[James Sweet]

These radios were the cheap consumer desktop radios before the transistor
radios took over.

They truly are a masterpiece of minimalist engineering. They cut every
corner that could be cut in the name of reducing the cost. Packed
components into the chassis however they would fit, wiring is a rat's
nest, little in the way of shielding, and yet they do work, pretty well
even, and many are still going fine a half century longer than they were
intended to last.

 

[[email protected]]

| In article <[email protected]>, [email protected]
| wrote:
|
|> Does anyone have a 500 kV AC line directly to their home? No.
|>
|> OTOH, 220VDC would bother me more than 480VAC.
|
| Why? Switching could be more of a problem with no zero crossings.

That *IS* why 220 VDC would bother more to have it running through my home
than having 480 VAC running through my home.


| 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.

I don't want that much DC coming into my home, especially with utility fault
currents.

I would draw the line at 600 volts for AC, and 48 volts for DC.

 

[[email protected]]

|
| [email protected] 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.
|>
|> If using Edison's 220/110VDC split system, even a couple miles would be way
|> too far. Today would could do transmission, distribution, service, and
|> utilization, and different DC voltages and keep it DC all the way. It would
|> still not be as cheap as AC, but it is possible to do.
|
|
| Yawn. You could post something that makes sense, but you rarely do.
| Lots of stupid things can be done, but why, other than to prove
| someone's ignorance?

So you don't really understand electricity, eh?

 

[[email protected]]

|
| [email protected] 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.
|>
|> And a filter that can remove 60 Hz (or whatever slow rate was in use back in
|> Edisn's day) could not clean up some modulated noise band at higher freqs?
|
|
| Did you even read what you posted? That is one of your most pathetic
| attempts at trolling, to date.

Do you even understand filters at all?

 

[[email protected]]

| In article <[email protected]>, [email protected]
| 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?

 

[[email protected]]

|
| [email protected] 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.
|>
|> 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.

 

[[email protected]]

|
| [email protected] wrote:
|>
|> |
|> | [email protected] 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.
|> |>
|> |> If using Edison's 220/110VDC split system, even a couple miles would be way
|> |> too far. Today would could do transmission, distribution, service, and
|> |> utilization, and different DC voltages and keep it DC all the way. It would
|> |> still not be as cheap as AC, but it is possible to do.
|> |
|> |
|> | Yawn. You could post something that makes sense, but you rarely do.
|> | Lots of stupid things can be done, but why, other than to prove
|> | someone's ignorance?
|>
|> So you don't really understand electricity, eh?
|
|
| Projecting your failings again, or just another pathetic attempt at
| trolling?

Actually, it is your inability to understand what you read that is a problem.
In school, there was a subject called "reading comprehension". I guess you
flunked that subject.