Whole house "battery" wiring/power...

[Don Kelly]

From my reading, the problem of capacitive reactance is also minimized
with the DC transmission lines.

That too, and that is a major benefit. However, there is still a reactive
problem at the receiving end where it is necessary to have the capacity to
supply reactive. This will be dependent on load and the particular control
of the system as a whole. For long lines this will be less than what would
otherwise be needed to compensate for line capacitance.

 

[The Daring Dufas]

YOU ARE SOUNDING LIKE AN IDIOT

HOW DO YOU SUUPLY REATIVE ?

YOU SHOULD COMMIT HAIKIRI

IT'S CALLED REACTANCE

AND I AM NOT GOING TO SHOW YOU HOW TO ACHIEVE THAT HERE NOR ANYWHERE
ELSE

YOU WILL HAVE TO PAY THE PIPER DONKEY LIKE EVERYONE ELSE

OR JUST SHUT THE FLUX UP

PERMAMNENTLY !

I AM PROTEUS

Uh, Pro, buddy, there is medication for your problem.
Your county health department may be able to help you
out with a psychiatric referral. FLNF

TDD

 

[bud--]

Uh, Pro, buddy, there is medication for your problem.
Your county health department may be able to help you
out with a psychiatric referral. FLNF

TDD

It is a particularly ignorant troll that infests alt.engineering.electrical.

Just ignore it like everyone else (except one of its equals).

 

[Jules]

I still have an old AC/DC radio from
those days, when radios were sold to work on either distribution
system.

Hmm, that triggered a memory. I used to have an AC/DC one from the '60s -
manual switch, and you could feed 12V DC in on the same power socket as
AC. I doubt something like that would pass H+S these days, never mind the
amount of people who'd try to feed it domestic AC with the switch on the
DC setting and fry the thing

cheers

Jules

 

[The Daring Dufas]

It is a particularly ignorant troll that infests
alt.engineering.electrical.

Just ignore it like everyone else (except one of its equals).

I was being fecesious {sic}.

TDD

 

[The Daring Dufas]

Thats why Westinghouse beat Edison in the early days of deciding what
electical distribution system to use, Westinghouse (scientist) wanted
AC, Edison (who was more of an inventor than a scientist) would not
let go of his prejudice for DC. I still have an old AC/DC radio from
those days, when radios were sold to work on either distribution
system.

Have you had any experience with high frequency AC power systems?
I've come across 400hz AC power in some old computer installations
and seen a lot of military surplus aircraft power equipment that
used 400hz AC power. My assumption has always been that higher the
frequency, the smaller the mass of the transformers not only making
equipment smaller but lighter.

TDD

 

[Don Kelly]

message





Even a 5Kw 6 phase converter was a sight to see- looked like an octopus
with glowing arms and a bright spot dancing on a dish of mercury.
Seriously the advantages of DC transmission has relatively little to do
with
skin effect as conductors are typically ACSR with aluminum on the outside
and steel inside- and, at these voltages are grouped in bundles. The size
of the conductor has more to do with mechanical than electrical
properties.
DC transmission at high voltages is economical for long lines where the
reduced cost of the line exceeds the added cost of the terminal equipment.
There are also some other technical advantages . This breakeven point is
at
a much shorter distance for underground or underwater cable. DC back to
back
terminals are often used where frequency differences (e.g. in Japan with
both 50 and 60 Hz systems) or stability concerns arise. They do have the
disadvantage that reasonable and economic circuit breakers for DC don't
exist and this means that the system is essentially point to point rather
than through an interconnected grid. In addition, conversion from one
voltage level to the next is bloody expensive, awkward and inefficient
compared to the use of AC transformers.
At low voltages, even for relatively short distances, DC is not a viable
option.

--
Don Kelly
[email protected]
cross out to reply- Hide quoted text -

- Show quoted text -

Thats why Westinghouse beat Edison in the early days of deciding what
electical distribution system to use, Westinghouse (scientist) wanted
AC, Edison (who was more of an inventor than a scientist) would not
let go of his prejudice for DC. I still have an old AC/DC radio from
those days, when radios were sold to work on either distribution
system.

Westinghouse was an inventor, and entrepreneur (as was Edison) - who
recognized good ideas when he saw them and a way to get around Edison's
stranglehold on the electrical "lighting" systems. This was weakened before
Tesla, by Gaulard and Gibbs who invented the transformer (1886 or
thereabouts for the first AC transmission). - making long distance
transmission possible. polyphase machines invented by Tesla were the icing
on the cake, and 3 phase systems followed soon after. Edison wanted to hang
onto his empire- so fought tooth and nail against AC- he had a good thing
going. Tesla once worked for him but got shafted.
As for the radio- If I recall correctly, until the late 1920's all radios
were battery powered. Then AC/DC units came into use. Better ones used
transformers to get the various voltages, filament and plate (replacing the
old A and B batteries).
The typical smaller radios that were sold in the 40's and 50's would work
on DC as they did not have a transformer, and tubes operated on the
rectified line voltage, with tube filaments in series. This was done, not
with intent to use them on DC supplies but because they were considerably
cheaper to build but could have a hot chassis (safety? what's that?).

The history of those times is very interesting. An often ignored inventor
who thought things out before trying them (as opposed to the Edison
approach) , was Elihu Thompson.

 

[Don Kelly]

Very common (standard?) in aircraft.

In addition to smaller generator/motor and transformer sizes and weights
for a given power, the 400Hz machines can be driven at higher speeds
eliminating some or all gearing in high rpm aircraft usage (up to 24000
rpm at 400 Hz
vs up to 3600 rpm at 60 Hz. ).
For aircraft the distances involved are short so that inductance and
capacitance are not a problem .

In general, for land based applications the advantages are outweighed by the
disadvantages because of the distances involved.

Switching power supplies were not an option in those days.

 

[The Daring Dufas]

Thats why Westinghouse beat Edison in the early days of deciding what
electical distribution system to use, Westinghouse (scientist) wanted
AC, Edison (who was more of an inventor than a scientist) would not
let go of his prejudice for DC. I still have an old AC/DC radio from
those days, when radios were sold to work on either distribution
system.

Westinghouse was an inventor, and entrepreneur (as was Edison) - who
recognized good ideas when he saw them and a way to get around Edison's
stranglehold on the electrical "lighting" systems. This was weakened
before Tesla, by Gaulard and Gibbs who invented the transformer (1886
or thereabouts for the first AC transmission). - making long distance
transmission possible. polyphase machines invented by Tesla were the
icing on the cake, and 3 phase systems followed soon after. Edison
wanted to hang onto his empire- so fought tooth and nail against AC- he
had a good thing going. Tesla once worked for him but got shafted.
As for the radio- If I recall correctly, until the late 1920's all
radios were battery powered. Then AC/DC units came into use. Better
ones used transformers to get the various voltages, filament and plate
(replacing the old A and B batteries).
The typical smaller radios that were sold in the 40's and 50's would
work on DC as they did not have a transformer, and tubes operated on the
rectified line voltage, with tube filaments in series. This was done,
not with intent to use them on DC supplies but because they were
considerably cheaper to build but could have a hot chassis (safety?
what's that?).

The history of those times is very interesting. An often ignored
inventor who thought things out before trying them (as opposed to the
Edison approach) , was Elihu Thompson.

When I was a kid, I got hold of an old tube type record player
that had a metal chassis, for some reason when I was playing
around with it on the back porch of our house, I got lit up.
DANG!! This was long before two wire cords had a wide bladed
neutral. With all the electrical devices I played with when
I was a kid, I'm surprised I ever survived.

TDD

 

[Don Kelly]

When I was a kid, I got hold of an old tube type record player
that had a metal chassis, for some reason when I was playing
around with it on the back porch of our house, I got lit up. DANG!! This
was long before two wire cords had a wide bladed
neutral. With all the electrical devices I played with when
I was a kid, I'm surprised I ever survived.

TDD

 

[James Sweet]

Thats why Westinghouse beat Edison in the early days of deciding what
electical distribution system to use, Westinghouse (scientist) wanted
AC, Edison (who was more of an inventor than a scientist) would not
let go of his prejudice for DC. I still have an old AC/DC radio from
those days, when radios were sold to work on either distribution
system.

AC/DC radios were born out of the great depression. It was the
Volkswagen Beetle of radios. The reason for the design was that it
eliminated the (expensive) power transformer by wiring all the tube
heaters in series and made the set much cheaper to manufacture. A useful
side effect of this was that it would work on either AC or DC. An
additional potentially very dangerous side effect is that depending on
which way the plug was inserted into the receptacle, the entire metal
chassis could be live, including shafts that would be exposed by a
missing knob.

The classic "All American Five" so named for the lineup of five tubes
used in virtually all of them was prolific up into at least the mid 60s.
It really is remarkable just how well it worked, despite circuit layout
and wiring techniques that would make an RF engineer cringe. It is
highly advisable to power these from an isolation transformer.

Incidentally, I read a few years back that it wasn't until the late
1990s that the last DC service was disconnected from a building,
somewhere in NY I think. I was amazed by how long it remained in use.

 

[James Sweet]

Hmm, that triggered a memory. I used to have an AC/DC one from the '60s -
manual switch, and you could feed 12V DC in on the same power socket as
AC. I doubt something like that would pass H+S these days, never mind the
amount of people who'd try to feed it domestic AC with the switch on the
DC setting and fry the thing

cheers

Jules

That's actually a bit different. The AC/DC radios he refers to use a
transformerless power supply with the tube heaters wired in series.
Yours likely wires the tube heaters in parallel with a vibrator to
supply B+ to the plates when running from batteries.

The worst offenders for radios being plugged into the wrong voltage are
32V farm radios. The old 32VDC rural systems used the same plugs and
receptacles as the 110VAC systems standard elsewhere, so it's common for
someone unknowledgeable to plug a farm radio into a 120V receptacle and
blow all the tube heaters.

 

[James Sweet]

Have you had any experience with high frequency AC power systems?
I've come across 400hz AC power in some old computer installations
and seen a lot of military surplus aircraft power equipment that
used 400hz AC power. My assumption has always been that higher the
frequency, the smaller the mass of the transformers not only making
equipment smaller but lighter.

TDD

That's exactly it. 400Hz power has been standard in aircraft for many
decades. Not only are the transformers smaller and lighter, but the
generators and motors too, and the filter capacitors in power supplies.

It's the reason switchmode power supplies run in the tens of kHz, and
some small ones are running as high as 1MHz. As the frequency increases,
switching losses in the semiconductors increase, but the size of the
energy storage components (inductors, transformers, capacitors)
decreases. A 60Hz transformer capable of supplying 300W might 15 lbs,
but a 20kHz transformer capable of the same power is less than a pound
and far more compact.

 

[James Sweet]

Quite a few people were killed by putting radios in the bathroom. Reach
out of the bath or shower to tune the radio with a missing or damaged
knob and zap. Feet in water with body salts and whatnot with a grounded
drain fitting and hand on a live surface, that's about the worst case
scenario without actually *trying* to electrocute yourself.

 

[Archimedes' Lever]

IT'S CALLED REACTANCE

Yeah, dipshit... That is the response to magnetic flux and work.

It is referred to by ALL of us in the industry, as a reactive load.

Go away, you know nothing twit.

 

[Archimedes' Lever]

Uh, Pro, buddy, there is medication for your problem.
Your county health department may be able to help you
out with a psychiatric referral. FLNF

TDD

Are you kidding? We are talking about NYC here. To them, his nut case
level is mild.

 

[Archimedes' Lever]

Edison (who was more of an inventor than a scientist) would not
let go of his prejudice for DC.

^^^^^^^^^^^^^^^^
Idiot. It is prejudice AGAINST AC.

It is a derogatory term, so there is no prejudice FOR anything.

 

[Archimedes' Lever]

Very common (standard?) in aircraft.

Yes, silly. 400Hz is still the standard for aviation.

Use some sense. Why would they *downgrade* to a heavier system with
zero co-compatibility?

 

[Archimedes' Lever]

Filter capacitors and inductors too. It's not uncommon for switching
power supplies to be above 1MHz, also to keep the size of components
(and costs) small.

...and transformers get *very* big at DC.

I want a citation that switchers are commonly running at and above
1MHz.

NONE of ours did.

 

[Archimedes' Lever]

When I was a kid, I got hold of an old tube type record player
that had a metal chassis, for some reason when I was playing
around with it on the back porch of our house, I got lit up.
DANG!! This was long before two wire cords had a wide bladed
neutral. With all the electrical devices I played with when
I was a kid, I'm surprised I ever survived.

TDD

Somehow my hand ended up between the poles of a 10kV Jacob's ladder on
day, while sitting indian style in front of it.

It shot me back about seven feet (my legs). I am sure I clamped the
supply down to near nothing, since it was only a 10mA furnace ignition
transformer.

That one was phase independent. Surprised I survived my youth as well.
I made a shock box "lie detector" as a science project, and was
shocking parents with it... mostly. Back then, a kid could get away
with that stuff.