Moire and superconductivity

[John Larkin]

On Sat, 3 Aug 2019 13:11:32 +0100, Martin Brown
<'''newspam'''@nezumi.demon.co.uk> wrote:

On 02/08/2019 20:41, Rick C wrote:
On Friday, August 2, 2019 at 3:04:38 PM UTC-4, John Larkin wrote:
On Fri, 2 Aug 2019 10:17:57 +0000 (UTC),
DecadentLinuxUserNumeroUno@decadence.org wrote:

Rick C <gnuarm.deletethisbit@gmail.com> wrote in news:61d6a7e5-c88a-
4c82-a288-9afb115e0f52@googlegroups.com:

How many in this group still don't have smart phones?

I have two phones, both smart. One I use for calls, but get spam
calls all the time. The other I only use for weather and data, like
DLing music and movies, which I then move over to my PC. I don't make
calls on it, but it still gets spam calls, just not as many.

My friend SPOKE to his doctor about bladder stuff, and less than a
day later, he starts getting spam on his phone about urologists. Never
looked at a site and never texted anything about it.

This behavior of these spammers should be declared as criminal.

I have a flip phone that's just a telephone; no texting, no voice
messaging, nothing. I get maybe one spam phone call a week.

I recharge it maybe every two weeks.

If you only charge it once in two weeks, you can't be using it much. They can lower current at idle, but they can't reduce the transmit power much.

If you don't use it, why have it? Or are you exaggerating the run time?

I believe him. My trusty old Nokia dumb phone would go about two weeks
on a charge. I didn't have it clamped permanently to my head like some
do but it would last that long with reasonable call usage and even
longer in standby mode and/or in cities where the signal was stronger.

When I dropped it in a bucket of water by accident it stopped working
and I got a Moto G3 based on it having the best battery life of any
smart phone available at the time. It would last about 7 days normal use
when new - down to about 3 days now with an elderly battery.

My wife's new iPhone X requires a recharge every single day (as did its
6 series predecessor). Usage profile on both phones broadly similar.

Hers gets a bit more hammer on Google maps and mobile data.

The demo on my Casio Rock was to run over it with a jeep. It seems
indestructible.

I must run about 5 minutes a week. Mo calls me to say "I'll be over
there in 10 minutes" and I say "Fine, take your time" and get ready to
go. I think about 6 people have my cell number, and only one is a
customer. He's a Fellow of United Technologies. He can call me at 3AM
if he wants to.

(Mo walks 5 minutes from where she works, to my shop, and we hike a
footbridge over US101 to where I park my car and drive home together.
The Brat works down the hall from me, and her guy has the office next
to Mo. Nice coincidence, in a place where hour-long commutes are not
unusual.)

One consequence of technology is to cram absurd densities of over-paid
geeks into a few small patches of land. It's not surprising that birth
rates are down.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Jasen Betts]

On 2019-08-03, George Herold <gherold@teachspin.com> wrote:

Three phase. That's was Tesla's big concept. Some people wanted Niagra
to generate DC.
Three phase is the only induction motor that is easy to understand.
I guess it's mostly the same for a generator. (but backwards..
is there some battery/ power supply to help get it started as a
generator?)

if needed that can be done, but usually thr rotor retains enough
magnetism to bootstrap enough voltage for the field current.

--
When I tried casting out nines I made a hash of it.

 

On Fri, 02 Aug 2019 08:43:55 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

I heard they're going to upgrade the hydro-plant at Niagara
Falls. How much better will the new one be?* (In now is one
built in the 60's. Iron and copper spinning around. I know
almost nothing about hydro generation, are the generators
multi phase?)

All power plant size generators have been three phase for at least a
century.

Three phase. That's was Tesla's big concept. Some people wanted Niagra
to generate DC.

Of course, Tesla thought that you needed six wires, two for each
phase, to connect a generator to a motor.

It is true that you need two wires on each phase if you insist of
using two phase with 90 degree phase shift. Tesla must have known that
by combining the return wires of all three phases to a common neutral
the return currents cancel out. So if there is no current flowing in
the common neutral wire, why install it in the first place ?Thus a two
phase (90 degree) system requires 4 wires, a balanced three phase
system only three.

Two phases is the minimum number of phases which will produce a
rotating magnetic field and hence an electric motor will always start
and it will rotate in the well defined direction, either CW or CCW.

A motor can be run with a single phase, but it might not start and if
it starts, might sometimes rotate in CW direction while at other times
in CCW direction.

In practice current "single phase" motors are actually two phase
motors with a big capacitor to feed the other winding with 90 degree
phase shift. In old times before big starter capacitors, it was
assumed that it was easiest to deliver the phase shifted voltage from
the power plant as a separate phase.

No such issues with three phase motors, it will always start and
rotate in a consistent direction. If you want to change the rotation
direction, just swap two phase conductors and the motor will rotate in
opposite direction.

 

Jasen Betts <jasen@xnet.co.nz> wrote in
news:qi8s0t$966$3@gonzo.revmaps.no-ip.org:

On 2019-08-03, George Herold <gherold@teachspin.com> wrote:

Three phase. That's was Tesla's big concept. Some people wanted
Niagra to generate DC.
Three phase is the only induction motor that is easy to
understand. I guess it's mostly the same for a generator. (but
backwards.. is there some battery/ power supply to help get it
started as a generator?)

if needed that can be done, but usually thr rotor retains enough
magnetism to bootstrap enough voltage for the field current.

I used a '50s GM generator as a motor and powered a go-cart with it
back in 1971. The battery had no problem energizing the field coils.

AFAIK all power generation 'generators' have electrical stator
fields. If there are any that use/used permanent magnets, they must
be rare.

 

upsidedown@downunder.com wrote in
news:kfufke1ua8ddvmb9udqps7uoskl2d78de9@4ax.com:

On Fri, 02 Aug 2019 08:43:55 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

I heard they're going to upgrade the hydro-plant at Niagara
Falls. How much better will the new one be?* (In now is one
built in the 60's. Iron and copper spinning around. I know
almost nothing about hydro generation, are the generators
multi phase?)

All power plant size generators have been three phase for at least
a century.

Three phase. That's was Tesla's big concept. Some people wanted
Niagra to generate DC.

Of course, Tesla thought that you needed six wires, two for each
phase, to connect a generator to a motor.

It is true that you need two wires on each phase if you insist of
using two phase with 90 degree phase shift. Tesla must have known
that by combining the return wires of all three phases to a common
neutral the return currents cancel out. So if there is no current
flowing in the common neutral wire, why install it in the first
place ?Thus a two phase (90 degree) system requires 4 wires, a
balanced three phase system only three.

You need to examine the difference between Delta and Wye
configurations.

<https://www.civicsolar.com/question/delta-vs-wye-explained>

<https://www.belden.com/blog/data-centers/3-phase-power-wye-it-
matters>

Now think about what happens if a phase gets shorted or opens in
both configurations.

Which one can tolerate such a short and continue operating?

A lot of mission critical (data center) systems use Delta
configured feeds. A lot of blade servers require 208V AC power.

 

[George Herold]

On Monday, August 5, 2019 at 6:04:29 AM UTC-4, upsid...@downunder.com wrote:

On Fri, 02 Aug 2019 08:43:55 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

I heard they're going to upgrade the hydro-plant at Niagara
Falls. How much better will the new one be?* (In now is one
built in the 60's. Iron and copper spinning around. I know
almost nothing about hydro generation, are the generators
multi phase?)

All power plant size generators have been three phase for at least a
century.

Three phase. That's was Tesla's big concept. Some people wanted Niagra
to generate DC.

Of course, Tesla thought that you needed six wires, two for each
phase, to connect a generator to a motor.

It is true that you need two wires on each phase if you insist of
using two phase with 90 degree phase shift. Tesla must have known that
by combining the return wires of all three phases to a common neutral
the return currents cancel out. So if there is no current flowing in
the common neutral wire, why install it in the first place ?Thus a two
phase (90 degree) system requires 4 wires, a balanced three phase
system only three.

Two phases is the minimum number of phases which will produce a
rotating magnetic field and hence an electric motor will always start
and it will rotate in the well defined direction, either CW or CCW.

A motor can be run with a single phase, but it might not start and if
it starts, might sometimes rotate in CW direction while at other times
in CCW direction.

In practice current "single phase" motors are actually two phase
motors with a big capacitor to feed the other winding with 90 degree
phase shift. In old times before big starter capacitors, it was
assumed that it was easiest to deliver the phase shifted voltage from
the power plant as a separate phase.

No such issues with three phase motors, it will always start and
rotate in a consistent direction. If you want to change the rotation
direction, just swap two phase conductors and the motor will rotate in
opposite direction.

Thanks, Three phase motors are fairly easy. I don't understand the single phase
induction motors as well. (the phase slippage stuff.)


George H.