On 4/11/2011 3:57 AM Han spake thus:

David Nebenzahl wrote in news:4da29d48$0$26573
:

The intertie and the house's power connection are going to be at pretty
much exactly the same voltage. What happens is that the PV system is
connected *in parallel* with the grid; it's dumping more *current* into
the system, not more voltage.

http://www.northjersey.com/news/116938343
_Municipal_officials_throw_wrench_in_PSE_G_s_solar _paneling_program.html

or
http://tinyurl.com/3tcv4le

1. So what in the world does that have to do with the point I stated?
(Rhetorical question. Answer: nothing.)

2. Y'know, if you used a non-brain-damaged news client that didn't
mangle long URLs (unlike your Xnews), you wouldn't have to dick around
with those tinyurls.


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On 4/11/2011 10:32 AM harry spake thus:

The modern grid tie/connected "transformerless" inverter manipulates
the DC output from the panels so that they run on their "sweet spot"
ie the most efficient voltage and current. It self connects/
disconnects to the mains as and when there is sufficient light operate
the panels. I t uses the mains sine wave to generate it's own sine
wave on the AC side. The current delivered is indeed dependant on the
output voltage it dleivers to "push2 that current back into the
mains.

Bull****.

Bit on the topic here.
http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws
http://en.wikipedia.org/wiki/Grid_tie_inverter

Apparently you didn't even *read* that second article. It says:

The grid tie inverter must synchronize its frequency with that of the
grid (e.g. 50 or 60 Hz) using a local oscillator and limit the voltage
to no higher than the grid voltage.

Re-read that last phrase: "limit the voltage to no higher than the grid
voltage".

You don't "push" electricity from your solar installation into the grid
by raising the voltage, as someone here postulated. It just don't work
that way.



--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On 4/11/2011 2:01 PM, David Nebenzahl wrote:
On 4/11/2011 10:32 AM harry spake thus:

The modern grid tie/connected "transformerless" inverter manipulates
the DC output from the panels so that they run on their "sweet spot"
ie the most efficient voltage and current. It self connects/
disconnects to the mains as and when there is sufficient light operate
the panels. I t uses the mains sine wave to generate it's own sine
wave on the AC side. The current delivered is indeed dependant on the
output voltage it dleivers to "push2 that current back into the
mains.

Bull****.

Bit on the topic here.
http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws
http://en.wikipedia.org/wiki/Grid_tie_inverter

Apparently you didn't even *read* that second article. It says:

The grid tie inverter must synchronize its frequency with that of the
grid (e.g. 50 or 60 Hz) using a local oscillator and limit the voltage
to no higher than the grid voltage.

Re-read that last phrase: "limit the voltage to no higher than the grid
voltage".

You don't "push" electricity from your solar installation into the grid
by raising the voltage, as someone here postulated. It just don't work
that way.


I remember a I & V limiting bench power supply I owned back when I
worked as a repair tech at a service depot. Under certain circumstances,
when I cranked the voltage control to raise the voltage, the voltage
stayed put but the current would rise. I wonder if that's the sort of
thing that happens when these grid connected inverters are used?

TDD

David Nebenzahl wrote in
s.com:

On 4/11/2011 3:57 AM Han spake thus:

David Nebenzahl wrote in
news:4da29d48$0$26573 :

The intertie and the house's power connection are going to be at
pretty much exactly the same voltage. What happens is that the PV
system is connected *in parallel* with the grid; it's dumping more
*current* into the system, not more voltage.

http://www.northjersey.com/news/116938343
_Municipal_officials_throw_wrench_in_PSE_G_s_solar _paneling_program.ht
ml

or
http://tinyurl.com/3tcv4le

1. So what in the world does that have to do with the point I stated?
(Rhetorical question. Answer: nothing.)

I was agreeing with your statement of parallel systems, and offered a
picture to sort of substantiate.

2. Y'know, if you used a non-brain-damaged news client that didn't
mangle long URLs (unlike your Xnews), you wouldn't have to dick around
with those tinyurls.

Sorry, I'm staying with Xnews for a while longer.

Have a wonderful day, David ...

--
Best regards
Han
email address is invalid

On 4/10/2011 22:12 PM, m II wrote:


"daestrom" wrote in message ...

On 4/6/2011 19:31 PM, m II wrote:
The fault capacity of a household main breaker or fuses is not an issue,
unless very old technology, like you.
One hundred feet of twisted triplex supply cable limits faults to well
within the fault tolerances.


Got some numbers/calculations to support that? Is that including the
next door neighbors with their PV installation?

daestrom

-------------------

Sure! Basic Ohms lawa and a wire resistance table

http://en.wikipedia.org/wiki/American_wire_gauge

A 200 ampere service running 240 Vac and only considering the straight
resistance of copper (many use AL outside conductors these days).
and considering the street transformer as an infinite current supply (0
Ohms impedance)

The chart shows we would use 2/0 copper (assuming solid copper, but it
won't be)

In a 100 feet of overhead run to a house, down the stack and through the
meter to the main panel, where the fuses or breakers are, not
considering the impedance of the overcurrent devices (that allegedly
cannot handle a fault this big) we come up a with a minimum copper
resistance of

200 feet (has to return) x 0.07793 x 10^-3 Ohms / foot (oh look ...your
old units too) = 0.015586 Ohms

Using 240 Vac as the fault supply (it won't be under a faulted
condition) the max fault current would be

240 Vac / 0.015586 Ohms = 15.4 kA.

Now we havent figured in any of the other impedances (very generous)
and any approved O/C device in a panel these days is rated at 100kA.

Only problem with that is that many home service panels use breakers
with an AIR of only 10kA, not 100kA. (my old house, built in 2000 was
10kA, and my new one, built in 2010 is also 10kA, both perfectly correct
by code)

Here's are some modern service panels that come with 10k AIR breakers.
http://static.schneider-electric.us/...ad-centers.pdf

And how many homes in the utilities service area are even up to current
code? I'd bet many homes in many service areas have only 10kA AIR.

The utility that is being ultra-conservative may have to consider that
older homes in their service area may not even support this.

Can you just imagine the hue and cry when some homeowners are told they
have to spend a couple hundred bucks to upgrade their service panel
because of changes in the utility's distribution?

daestrom

On Apr 11, 1:32*pm, harry wrote:

Not he's got it right except for the fact that allr otating electric
lmachinary is AC.


I love how you can state that without any sort of qualification...

You seem to have forgotten about higher end bathroom fans
which use an inverter to operate a DC motor which is much
quieter than an AC motor...

AND

Light Rail vehicles are operated on DC systems which drive
HUGE traction motors with either an overhead wire or third
rail using the other rails as a one-way return path through
the vehicle chassis...

This is 600VDC and up, and WILL kill you if you make
any mistakes around it...

Those two quite common examples seem to refute your
absolute determination that ALL rotating electric machinery
is operated with AC motors...

~~ Evan

"Evan" wrote in message
...
On Apr 11, 1:32 pm, harry wrote:

Not he's got it right except for the fact that allr otating electric
lmachinary is AC.

Those two quite common examples seem to refute your
absolute determination that ALL rotating electric machinery
is operated with AC motors...

How so?

Vaughn

On 4/11/2011 2:42 PM Evan spake thus:

On Apr 11, 1:32 pm, harry wrote:

Not he's got it right except for the fact that allr otating
electric lmachinary is AC.

I love how you can state that without any sort of qualification...

.... especially when it's pure BS. But that's our Harry.

You seem to have forgotten about higher end bathroom fans
which use an inverter to operate a DC motor which is much
quieter than an AC motor...

Welll, since this is a.h.r, and since you're picking a nit, let me pick
yours. I've installed several "higher-end" vent fans (Panasonic), all of
which use AC induction motors which are very quiet. Which bath fans use
the setup you described? (Besides which, why in the world would you need
an "inverter" to run a DC motor from an AC supply? Perhaps you meant
"rectifier"?)


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On Mon, 11 Apr 2011 14:21:20 -0500, The Daring Dufas
wrote:

On 4/11/2011 2:01 PM, David Nebenzahl wrote:
On 4/11/2011 10:32 AM harry spake thus:

The modern grid tie/connected "transformerless" inverter manipulates
the DC output from the panels so that they run on their "sweet spot"
ie the most efficient voltage and current. It self connects/
disconnects to the mains as and when there is sufficient light operate
the panels. I t uses the mains sine wave to generate it's own sine
wave on the AC side. The current delivered is indeed dependant on the
output voltage it dleivers to "push2 that current back into the
mains.

Bull****.

Bit on the topic here.
http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws
http://en.wikipedia.org/wiki/Grid_tie_inverter

Apparently you didn't even *read* that second article. It says:

The grid tie inverter must synchronize its frequency with that of the
grid (e.g. 50 or 60 Hz) using a local oscillator and limit the voltage
to no higher than the grid voltage.

Re-read that last phrase: "limit the voltage to no higher than the grid
voltage".

You don't "push" electricity from your solar installation into the grid
by raising the voltage, as someone here postulated. It just don't work
that way.


I remember a I & V limiting bench power supply I owned back when I
worked as a repair tech at a service depot. Under certain circumstances,
when I cranked the voltage control to raise the voltage, the voltage
stayed put but the current would rise. I wonder if that's the sort of
thing that happens when these grid connected inverters are used?

To "push" power back into the pipe the generator's phase leads the line's, so
in a sense the generator's voltage is greater than the lines (as someone
pointed out Kirchhoff didn't lie).

On Mon, 11 Apr 2011 17:54:33 -0400, "vaughn"
wrote:


"Evan" wrote in message
...
On Apr 11, 1:32 pm, harry wrote:

Not he's got it right except for the fact that allr otating electric
lmachinary is AC.

Those two quite common examples seem to refute your
absolute determination that ALL rotating electric machinery
is operated with AC motors...

How so?


Look deeper in the motor. It's all AC on the inside. ;-)

wrote in message
...
Those two quite common examples seem to refute your
absolute determination that ALL rotating electric machinery
is operated with AC motors...

How so?


Look deeper in the motor. It's all AC on the inside. ;-)

Exactly!

Vaughn

"daestrom" wrote in message ...
Only problem with that is that many home service panels use breakers
with an AIR of only 10kA, not 100kA. (my old house, built in 2000 was
10kA, and my new one, built in 2010 is also 10kA, both perfectly correct
by code)

Here's are some modern service panels that come with 10k AIR breakers.
http://static.schneider-electric.us/...ad-centers.pdf

And how many homes in the utilities service area are even up to current
code? I'd bet many homes in many service areas have only 10kA AIR.

The utility that is being ultra-conservative may have to consider that
older homes in their service area may not even support this.

Can you just imagine the hue and cry when some homeowners are told they
have to spend a couple hundred bucks to upgrade their service panel
because of changes in the utility's distribution?

daestrom

-----------

Well that situation would be unfortunate and impossible to regulate as
`legal, not conforming`

This is not a problem here as 10kA hasn`t been passed for many years. I
believe any Canuck panels have to to have the class `R`or rejection fuse
holders so that only the nasty electricians can force an old `code` fuse
into the holder. The 100kA fuses have been promoted for a few decades with
the seriousness getting more severe in later years. I thought they were
actually not allowed, here, anymore. This may be incorrect. More research
would be required to verify.

Either way the 10kA doesn't take much more impedance to drop it down with a
few added factors mentioned in my previous text. Most of our service feeds
are (ACSR) aluminum conductor, steel reinforced, and present higher
impedances. I don`t see some small cogen circuit at the end of a few hundred
feet of grid (mine plus yours) being a fault capacity concern in a
residenial environment.

Having said that I guy up the street is just finishing installing 200kW or
more of PV panels. Wait until they produce nothing all winter as they were
snowed in most of last winter being at a low slope. The hook up wasn't`t
completed so he won`t find out until next winter...LOL See how much
harmonic crap we get on the street when they go online.


mike

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On Apr 11, 8:01*pm, David Nebenzahl wrote:
On 4/11/2011 10:32 AM harry spake thus:

The modern grid tie/connected "transformerless" inverter manipulates
the DC output from the panels so that they run on their "sweet spot"
ie the most efficient voltage and current. It self connects/
disconnects to the mains as and when there is sufficient light operate
the panels. I t uses the mains sine wave to generate it's own sine
wave on the AC side. The current delivered is indeed dependant on the
output voltage it dleivers *to "push2 that current back into the
mains.

Bull****.

Bit on the topic here.
http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws
http://en.wikipedia.org/wiki/Grid_tie_inverter

Apparently you didn't even *read* that second article. It says:

* *The grid tie inverter must synchronize its frequency with that of the
* *grid (e.g. 50 or 60 Hz) using a local oscillator and limit the voltage
* *to no higher than the grid voltage.

Re-read that last phrase: "limit the voltage to no higher than the grid
voltage".

You don't "push" electricity from your solar installation into the grid
by raising the voltage, as someone here postulated. It just don't work
that way.

--
The current state of literacy in our advanced civilization:

* *yo
* *wassup
* *nuttin
* *wan2 hang
* *k
* *where
* *here
* *k
* *l8tr
* *by

- from Usenet (what's *that*?)

Yes it does. Electrical current flows from a point of higher
potential to a lower point. The very first thing you learn. Ohm's Law.

On 4/11/2011 6:16 PM, zzzzzzzzzz wrote:
On Mon, 11 Apr 2011 17:54:33 -0400,
wrote:


wrote in message
...
On Apr 11, 1:32 pm, wrote:

Not he's got it right except for the fact that allr otating electric
lmachinary is AC.

Those two quite common examples seem to refute your
absolute determination that ALL rotating electric machinery
is operated with AC motors...

How so?


Look deeper in the motor. It's all AC on the inside. ;-)

I think you are pushing it....the brushes on a dc motor "guide" the dc
to different windings.....it is still dc...

In an ac motor the windings are generally in parallel...all the ac is
applied at one time....

I think I got that right....is a long time since I covered motor
theory..grin...the ac is not "chopped up"....or guided anywhere....

You could say that all electric motors operate the same....as they all
depend on magnetism (all generally used motors...there are some operate
on static electricity, etc)
have fun...sno

--
Correct Scientific Terminology:
Hypothesis - a guess as to why or how something occurs
Theory - a hypothesis that has been checked by enough experiments
to be generally assumed to be true.
Law - a hypothesis that has been checked by enough experiments
in enough different ways that it is assumed to be truer then a theory.
Note: nothing is proven in science, things are assumed to be true.

On Apr 11, 8:21*pm, The Daring Dufas
wrote:
On 4/11/2011 2:01 PM, David Nebenzahl wrote:





On 4/11/2011 10:32 AM harry spake thus:

The modern grid tie/connected "transformerless" inverter manipulates
the DC output from the panels so that they run on their "sweet spot"
ie the most efficient voltage and current. It self connects/
disconnects to the mains as and when there is sufficient light operate
the panels. I t uses the mains sine wave to generate it's own sine
wave on the AC side. The current delivered is indeed dependant on the
output voltage it dleivers to "push2 that current back into the
mains.

Bull****.

Bit on the topic here.
http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws
http://en.wikipedia.org/wiki/Grid_tie_inverter

Apparently you didn't even *read* that second article. It says:

The grid tie inverter must synchronize its frequency with that of the
grid (e.g. 50 or 60 Hz) using a local oscillator and limit the voltage
to no higher than the grid voltage.

Re-read that last phrase: "limit the voltage to no higher than the grid
voltage".

You don't "push" electricity from your solar installation into the grid
by raising the voltage, as someone here postulated. It just don't work
that way.

I remember a I & V limiting bench power supply I owned back when I
worked as a repair tech at a service depot. Under certain circumstances,
when I cranked the voltage control to raise the voltage, the voltage
stayed put but the current would rise. I wonder if that's the sort of
thing that happens when these grid connected inverters are used?

TDD- Hide quoted text -

- Show quoted text -

It's just another form of electricity generation in parallel with the
electricity grid. No different from any other form of generation. When
the PV array is generating the local voltage in the grid will rise a
little.
Or think of it another way. The current coming down the grid power
line will reduce as the PV panel takes up the local load, there will
be less voltage drop.
If the panel generates enough power the current in the grid will
reverse and the voltage close to the panel will be higher than the no
load grid voltage.

On Apr 11, 10:31*pm, daestrom wrote:
On 4/10/2011 22:12 PM, m II wrote:







"daestrom" wrote in ...

On 4/6/2011 19:31 PM, m II wrote:
The fault capacity of a household main breaker or fuses is not an issue,
unless very old technology, like you.
One hundred feet of twisted triplex supply cable limits faults to well
within the fault tolerances.

Got some numbers/calculations to support that? Is that including the
next door neighbors with their PV installation?

daestrom

-------------------

Sure! Basic Ohms lawa and a wire resistance table

http://en.wikipedia.org/wiki/American_wire_gauge

A 200 ampere service running 240 Vac and only considering the straight
resistance of copper (many use AL outside conductors these days).
and considering the street transformer as an infinite current supply (0
Ohms impedance)

The chart shows we would use 2/0 copper (assuming solid copper, but it
won't be)

In a 100 feet of overhead run to a house, down the stack and through the
meter to the main panel, where the fuses or breakers are, not
considering the impedance of the overcurrent devices (that allegedly
cannot handle a fault this big) we come up a with a minimum copper
resistance of

200 feet (has to return) x 0.07793 x 10^-3 Ohms / foot (oh look ...your
old units too) = 0.015586 Ohms

Using 240 Vac as the fault supply (it won't be under a faulted
condition) the max fault current would be

240 Vac / 0.015586 Ohms = 15.4 kA.

Now we haven’t figured in any of the other impedances (very generous)
and any approved O/C device in a panel these days is rated at 100kA.

Only problem with that is that many home service panels use breakers
with an AIR of only 10kA, not 100kA. (my old house, built in 2000 was
10kA, and my new one, built in 2010 is also 10kA, both perfectly correct
by code)

Here's are some modern service panels that come with 10k AIR breakers.http://static.schneider-electric.us/...ad-centers.pdf

And how many homes in the utilities service area are even up to current
code? *I'd bet many homes in many service areas have only 10kA AIR.

The utility that is being ultra-conservative may have to consider that
older homes in their service area may not even support this.

Can you just imagine the hue and cry when some homeowners are told they
have to spend a couple hundred bucks to upgrade their service panel
because of changes in the utility's distribution?

daestrom- Hide quoted text -

- Show quoted text -

Small scale locally generated power makes no difference to these
problems. In fact it helps.

On Apr 11, 10:42*pm, Evan wrote:
On Apr 11, 1:32*pm, harry wrote:



Not he's got it right except for the fact that allr otating electric
lmachinary is AC.

I love how you can state that without any sort of qualification...

You seem to have forgotten about higher end bathroom fans
which use an inverter to operate a DC motor which is much
quieter than an AC motor...

AND

Light Rail vehicles are operated on DC systems which drive
HUGE traction motors with either an overhead wire or third
rail using the other rails as a one-way return path through
the vehicle chassis...

This is 600VDC and up, and WILL kill you if you make
any mistakes around it...

Those two quite common examples seem to refute your
absolute determination that ALL rotating electric machinery
is operated with AC motors...

~~ Evan

All rotating machinery is AC. Some are fitted with a mechanical
rectifier/inverter called a comutator and brushes which ignorant
people somehow think run on a different principle. You need to get
into motor theory.

I don't know why you bring up rail traction. A hundred years ago
electrical traction was often DC transmission. However all this is
long abandoned even before the advent of semiconductors.
http://wiki.answers.com/Q/How_schrage_motor_works

Since the advent of semiconductors the efficiency and technology has
vastly improved
http://en.wikipedia.org/wiki/Inverte...equency_drives

On 4/11/2011 11:17 PM harry spake thus:

On Apr 11, 8:01 pm, David Nebenzahl wrote:

On 4/11/2011 10:32 AM harry spake thus:

The modern grid tie/connected "transformerless" inverter
manipulates the DC output from the panels so that they run on
their "sweet spot" ie the most efficient voltage and current. It
self connects/ disconnects to the mains as and when there is
sufficient light operate the panels. I t uses the mains sine wave
to generate it's own sine wave on the AC side. The current
delivered is indeed dependant on the output voltage it dleivers
to "push2 that current back into the mains.

Bull****.

Bit on the topic here.
http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws
http://en.wikipedia.org/wiki/Grid_tie_inverter

Apparently you didn't even *read* that second article. It says:

The grid tie inverter must synchronize its frequency with that of
the grid (e.g. 50 or 60 Hz) using a local oscillator and limit the
voltage to no higher than the grid voltage.

Re-read that last phrase: "limit the voltage to no higher than the
grid voltage".

You don't "push" electricity from your solar installation into the
grid by raising the voltage, as someone here postulated. It just
don't work that way.

Yes it does. Electrical current flows from a point of higher
potential to a lower point. The very first thing you learn. Ohm's Law.

How many things are wrong with what you wrote? let's see:

That's not Ohm's Law, not by a long shot. Do you even know what that is?

Yes, electricy flows from a point of higher potential (voltage) to a
lower point. But you're confusing voltage and current here, a common
rookie mistake.


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On Apr 11, 11:29*pm, David Nebenzahl wrote:
On 4/11/2011 2:42 PM Evan spake thus:

On Apr 11, 1:32 pm, harry wrote:

Not he's got it right except for the fact that allr otating
electric lmachinary is AC.

I love how you can state that without any sort of qualification...

... especially when it's pure BS. But that's our Harry.

You seem to have forgotten about higher end bathroom fans
which use an inverter to operate a DC motor which is much
quieter than an AC motor...

Welll, since this is a.h.r, and since you're picking a nit, let me pick
yours. I've installed several "higher-end" vent fans (Panasonic), all of
which use AC induction motors which are very quiet. Which bath fans use
the setup you described? (Besides which, why in the world would you need
an "inverter" to run a DC motor from an AC supply? Perhaps you meant
"rectifier"?)

--
The current state of literacy in our advanced civilization:

* *yo
* *wassup
* *nuttin
* *wan2 hang
* *k
* *where
* *here
* *k
* *l8tr
* *by

- from Usenet (what's *that*?)

Most fans are noisy due to bad fan blade design causing turbulence and/
or dynamic imbalance.
Noisy motors are defective, or if inverter run, it's a nasty cheap
inverter which does not produce a true sine wave.
Some other form of fan speed controls spoil the sine wave form too.
Resitance controls lead to slippage in induction motors which causes
noise especially in low speed settings.

On 4/11/2011 11:46 PM harry spake thus:

All rotating machinery is AC.

Really, Harry? Really?

Is the spindle motor in your DVD player AC? How about the spindle motor
on your hard drive?

You do agree that those are all examples of "rotating machinery", don't you?


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

On Apr 11, 5:44*pm, Jim Wilkins wrote:
On Apr 11, 10:28*am, Home Guy wrote:

...
Unless your invertors were set to operate at a slightly higher output
voltage. *Even just a few volts differential between the mains voltage
and the invertor output would mean that you could push current out into
the grid, and by doing that raise the local grid voltage slightly.-

This explains a lot about inverter technology, though not whether they
use a higher voltage, a leading phase angle or both to force power
into the line:http://www.solarpanelsplus.com/solar...r-Inverters-Wo...

jsw

Leading and lagging phase angles is nothing whatever to do with the
matter.
This refers to phase angle between the current and the voltage
driving it.
Inductive circuits are always lagging, capacitive circuits are always
leading, while resistive circuits are in phase.
See also power factor.
http://en.wikipedia.org/wiki/Power_factor
In practice the grid runs at a lagging power factor due to all the
motors connected.
Leading power factor systems are inherently unstable.

On Apr 3, 9:08*pm, Home Guy wrote:
We have a residential energy program here in Ontario (Canada) that I
really don't agree with (called the Micro-Fit program) where the
electricity from roof-mounted solar panels is purchased by the
provincial power authority (OPA) at something like 80 cents per kw-hour
(a crazy-high fee that will have to be subsidized by somebody - ie the
general population, taxpayers, etc).

I believe all the details for this can be found he

http://microfit.powerauthority.on.ca/

A neighbor of mine had a free evaluation done on his home to see how
many panels situated on his roof would generate how much electricity.

The problem he's facing is that two different levels of power
distribution (the city-owned municipal owned and operated company, and
the provincial or regional power supplier or distributor that either
supplies the electricity to our city or owns the high and medium-voltage
lines and sub-stations where the electricity is stepped down) are
pointing the finger at each other by stating that there is a capacity
problem caused by the other as the reason why his solar panel
installation (which he hasn't yet contracted to be installed) can't be
connected to the grid.

It's my impression that any electricy that he'd be generating would
essentially be 2-phase 208 volts (ie - identical to the service that
enters our homes) and this electricity would simply be inserted or wired
in parallel through a meter to his existing electrical service. *I don't
see how the capacity (or lack thereof) of the sub-station serving our
corner of the city plays any role as to whether or not our local grid
can accept and utilize the estimated 5 or 6 kw that his panels are
likely to put out at maximum.

This issue has recently come up as indicated by this:

-----------------
The OPA is proposing that all new microFIT applications submitted on or
after December 8, 2010, would need an offer to connect from their local
distribution company before the OPA issues a microFIT conditional offer
of contract. *The proposed rule change can be viewed here.

http://microfit.powerauthority.on.ca...10-December-8-...
------------------

According to this document:

http://microfit.powerauthority.on.ca...m-Overview.pdf

Page 18 shows the most likely connection scheme - which is to connect
the Microfit PV project to the grid on the customer's side of his load
meter (ie - "behind the meter" - the load meter that is).

My basic thesis here is that I think any argument about the capacity of
the "grid" (where-ever or what-ever the "grid" is) being at or near
capacity and thus the application for eligibility to get the green light
for approval is bogus. *We are talking about installations that can't
generate more than 10 kw - and more likely would only generate 5 or 6 kw
on a mid-summer day, with the bulk of that energy being consumed by the
home owner's own AC unit (I'm sure) with little or none to spare to be
injected back into the neighborhood grid.

Comments?

FLUX THEM - KEEP IT OFF THE GRID.
IF YOU CAN, JUST OPEN A SMALL LOCAL DISTRIBUTION NEYWORK TO A
NEIGHBORING SHOP, FAMILY, OR SMALL GROUP OF OFFSET TENANTS FOR A SET
FEE.
YOU DO NOT WANT YOUR ENERGY SYSTEM ON ANY NATIONALGRID, THEY FUNCTION
BEST IN THEIR OWN LOOPS....ANY ENERGY ADDITIVES WILL ADULTERATE THE
SUPPLY...EVEN IF IN A SMALL QUANTA.
NOT TO MENTION WHAT IT CAN DO TO YPUR SYSTEM, SHOULD IT SWITCH TRY TO
CONTROL YOURS WITHOUT PROPER ELECTRICAL/MECHANICAL CO-NOMENCLATURE.

PAT ECUM

On Apr 12, 7:21*am, sno wrote:
On 4/11/2011 6:16 PM, wrote:





On Mon, 11 Apr 2011 17:54:33 -0400,
wrote:

*wrote in message
....
On Apr 11, 1:32 pm, *wrote:

Not he's got it right except for the fact that allr otating electric
lmachinary is AC.

Those two quite common examples seem to refute your
absolute determination that ALL rotating electric machinery
is operated with AC motors...

How so?

Look deeper in the motor. *It's all AC on the inside. *;-)

I think you are pushing it....the brushes on a dc motor "guide" the dc
to different windings.....it is still dc...

In an ac motor the windings are generally in parallel...all the ac is
applied at one time....

I think I got that right....is a long time since I covered motor
theory..grin...the ac is not "chopped up"....or guided anywhere....

You could say that all electric motors operate the same....as they all
depend on magnetism (all generally used motors...there are some operate
on static electricity, etc)
have fun...sno

--
Correct Scientific Terminology:
Hypothesis - a guess as to why or how something occurs
Theory - a hypothesis that has been checked by enough experiments
* to be generally assumed to be true.
Law - a hypothesis that has been checked by enough experiments
* in enough different ways that it is assumed to be truer then a theory..
Note: nothing is proven in science, things are assumed to be true.- Hide quoted text -

- Show quoted text -

It is DC until the point of the brushes. As the commutator segments
pass under each brush the current in that armature circuit reverses.
(There are many circuits in armature obviously) There is AC in the
armature. The armature could not revolve if it were not so.
From the observer's point of view, the magnetic field in the armature
is virtually stationary (moves slightly depending on load). But the
armature is revolving inside it.

On 4/12/2011 1:27 AM, harry wrote:
On Apr 11, 8:21 pm, The Daring
wrote:
On 4/11/2011 2:01 PM, David Nebenzahl wrote:





On 4/11/2011 10:32 AM harry spake thus:

The modern grid tie/connected "transformerless" inverter manipulates
the DC output from the panels so that they run on their "sweet spot"
ie the most efficient voltage and current. It self connects/
disconnects to the mains as and when there is sufficient light operate
the panels. I t uses the mains sine wave to generate it's own sine
wave on the AC side. The current delivered is indeed dependant on the
output voltage it dleivers to "push2 that current back into the
mains.

Bull****.

Bit on the topic here.
http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws
http://en.wikipedia.org/wiki/Grid_tie_inverter

Apparently you didn't even *read* that second article. It says:

The grid tie inverter must synchronize its frequency with that of the
grid (e.g. 50 or 60 Hz) using a local oscillator and limit the voltage
to no higher than the grid voltage.

Re-read that last phrase: "limit the voltage to no higher than the grid
voltage".

You don't "push" electricity from your solar installation into the grid
by raising the voltage, as someone here postulated. It just don't work
that way.

I remember a I& V limiting bench power supply I owned back when I
worked as a repair tech at a service depot. Under certain circumstances,
when I cranked the voltage control to raise the voltage, the voltage
stayed put but the current would rise. I wonder if that's the sort of
thing that happens when these grid connected inverters are used?

TDD- Hide quoted text -

- Show quoted text -

It's just another form of electricity generation in parallel with the
electricity grid. No different from any other form of generation. When
the PV array is generating the local voltage in the grid will rise a
little.
Or think of it another way. The current coming down the grid power
line will reduce as the PV panel takes up the local load, there will
be less voltage drop.
If the panel generates enough power the current in the grid will
reverse and the voltage close to the panel will be higher than the no
load grid voltage.

You could set up an interesting classroom experiment using colored water
or oil and clear tubing. A little grid with tiny widgets turning
from the flow of liquid being fed from different directions. It could
be fun. The pressure would represent voltage and flow represent current.

TDD

On 4/12/2011 1:47 AM, David Nebenzahl wrote:
On 4/11/2011 11:17 PM harry spake thus:

On Apr 11, 8:01 pm, David Nebenzahl wrote:

On 4/11/2011 10:32 AM harry spake thus:

The modern grid tie/connected "transformerless" inverter
manipulates the DC output from the panels so that they run on
their "sweet spot" ie the most efficient voltage and current. It
self connects/ disconnects to the mains as and when there is
sufficient light operate the panels. I t uses the mains sine wave
to generate it's own sine wave on the AC side. The current
delivered is indeed dependant on the output voltage it dleivers
to "push2 that current back into the mains.

Bull****.

Bit on the topic here.
http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws
http://en.wikipedia.org/wiki/Grid_tie_inverter

Apparently you didn't even *read* that second article. It says:

The grid tie inverter must synchronize its frequency with that of
the grid (e.g. 50 or 60 Hz) using a local oscillator and limit the
voltage to no higher than the grid voltage.

Re-read that last phrase: "limit the voltage to no higher than the
grid voltage".

You don't "push" electricity from your solar installation into the
grid by raising the voltage, as someone here postulated. It just
don't work that way.

Yes it does. Electrical current flows from a point of higher
potential to a lower point. The very first thing you learn. Ohm's Law.

How many things are wrong with what you wrote? let's see:

That's not Ohm's Law, not by a long shot. Do you even know what that is?

Yes, electricy flows from a point of higher potential (voltage) to a
lower point. But you're confusing voltage and current here, a common
rookie mistake.


Please enlighten us oh great one. ^_^

TDD

harry wrote:

And how many homes in the utilities service area are even up to
current code? I'd bet many homes in many service areas have only
10kA AIR.

The utility that is being ultra-conservative may have to consider
that older homes in their service area may not even support this.

Can you just imagine the hue and cry when some homeowners are told
they have to spend a couple hundred bucks to upgrade their service
panel because of changes in the utility's distribution?

Small scale locally generated power makes no difference to these
problems. In fact it helps.

Our regional and municipal electricity distributors are not pointing the
finger at the capability or specs of residential service panels or
neighborhood distribution / stepdown transformers as the reason why they
won't let small-scale (less than 10kw) roof-top PV systems to connect to
the grid.

They are saying that the local sub-station doesn't have the "capability"
to allow for a handful (or perhaps even a single) small-scale PV systems
to be hooked up and they would need to "upgrade" the sub-station in some
way.

For more about this, see he

http://www.greenpowertalk.org/archiv...p/t-13885.html

And less relevant, he

http://www.canadianenergylaw.com/201...ofit-projects/

All the arguments put forward here about why homeowner-operated PV
systems (with nameplate rating under 10kw) are not being allowed to
connect to the grid through their own bi-directional revenue meter have
not addressed the issue as to how the connection of such a PV system can
possibly affect or influence the operation of the regional municipal
sub-station supplying power (at 20 kv?) to the neighborhood in
question. The sub-station is "insulated" from direct exposure to any
individual home by at least 1 step-down distribution transformer (in our
case, a ground-mounted distribution transformer supplying maybe 20 homes
- our electrical service runs underground - not on poles in our
neighborhood).

There may not yet even be a single residential PV system that's been
connected to the grid for the area being served by the sub-station in
question.

g wrote:

Unless your invertors were set to operate at a slightly higher
output voltage. Even just a few volts differential between the
mains voltage and the invertor output would mean that you could
push current out into the grid, and by doing that raise the local
grid voltage slightly.

The grid can be seen as a pretty rigid beast. No small puny inverter
in the sub 1000kW class will much affect the grid voltage as a whole.
When voltage of the converter is attempted to be raised, current will
flow into the grid of course. The voltage increase will hardly be
measurable, as electrical characteristics of the grid will adjust
dynamically.

At any one time, there is a certain load on the grid as a whole. When
Mr. Homeowner adds 10Kw from some solar panels, some other power
generating systems connected to the grid will (have to) reduce their
output. As a result the voltage stays the same overall.

Here's the problem:

Many of the load devices you find in a typical home (primarily electric
motors that run cooling systems, air conditioners, fridges and freezers)
are not capable of regulating their input voltage.

So when a secondary electricity source comes on-line (like a small PV
system) then in order to push it's current into the local grid it will
have to *try* to raise it's output voltage in order to see some current
flow. It might only be a few volts, maybe less.

But does that mean there will be a measurable net reduction in the
current being supplied by the high-voltage substation for that corner of
the city?

Not if your typical load device in homes surround the PV system will
simply operate at a higher wattage.

The only sort of load that can effectively be regulated by a slight
increase in local grid voltage are electric heaters. When you raise
their input voltage slightly, they will put out more BTU of heat, and if
their heat output set-point doesn't change, then their operational duty
cycle will change slightly.

But in the case of an AC compressor, the fact that it might be getting a
slightly higher input voltage because a neighboring house is feeding PV
power into the local grid won't mean that the AC compressor will reduce
it's current consumption from the municipal utility supplier because of
the extra current coming from a neighbor's roof-top solar array. It
just means the motor will use BOTH sources of current and (I suppose)
run a little hotter but in the end not do any extra cooling work in the
process (it's rotational speed won't change).

Same theory would hold true for lighting (incandescent especially). If
you raise the input voltage, you'll get more light output - the bulb
will simply consume all the juice it would normally get from the utility
in addition to that being supplied by the neighborhood PV system.

The only way that a neighborhood PV system can actually suppliment
municipal utility power is when the PV system is wired up as a dedicated
sole supply source for a few select branch circuits. The way I see it,
you have to feed certain select loads 100% from a PV system (ie -
disconnect them from the municipal energy source) if you're going to
make a meaningful contribution to the supply-side of a municipal or
city-wide grid.

On Apr 12, 3:07*am, harry wrote:
On Apr 11, 5:44*pm, Jim Wilkins wrote:

On Apr 11, 10:28*am, Home Guy wrote:

...
Unless your invertors were set to operate at a slightly higher output
voltage. *Even just a few volts differential between the mains voltage
and the invertor output would mean that you could push current out into
the grid, and by doing that raise the local grid voltage slightly.-

This explains a lot about inverter technology, though not whether they
use a higher voltage, a leading phase angle or both to force power
into the line:http://www.solarpanelsplus.com/solar...r-Inverters-Wo...

jsw

Leading and lagging phase angles is nothing whatever to do with the
matter.
This refers to *phase angle between the current and the voltage
driving it.
Inductive circuits are always lagging, capacitive circuits are always
leading, while resistive circuits are in phase.
See also power factor.http://en.wikipedia.org/wiki/Power_factor
In practice the grid runs at a lagging power factor due to all the
motors connected.
Leading power factor systems are inherently unstable.

This explains generator output regulation by varying voltage:
http://www.basler.com/downloads/VR_parallel.pdf

and this the effect on current in or out of a synchronous generator
caused by varying the leading/lagging phase angle between the internal
magnetic field and the line voltage:
http://nptel.iitm.ac.in/courses/IIT-...II/pdf/2_3.pdf

jsw

On 4/11/2011 4:31 PM, daestrom wrote:
On 4/10/2011 22:12 PM, m II wrote:


"daestrom" wrote in message ...

On 4/6/2011 19:31 PM, m II wrote:
The fault capacity of a household main breaker or fuses is not an issue,
unless very old technology, like you.
One hundred feet of twisted triplex supply cable limits faults to well
within the fault tolerances.


Got some numbers/calculations to support that? Is that including the
next door neighbors with their PV installation?

daestrom

-------------------

Sure! Basic Ohms lawa and a wire resistance table

http://en.wikipedia.org/wiki/American_wire_gauge

A 200 ampere service running 240 Vac and only considering the straight
resistance of copper (many use AL outside conductors these days).
and considering the street transformer as an infinite current supply (0
Ohms impedance)

This is a fatal flaw in your argument. Transformers are not infinite
sources. A utility transformer might supply a fault current 20x the
rated current (for a "5% impedance" transformer). (While a transformer
will supply a fault current larger than the rated current that is not
likely with PV. PV is basically a constant current source.)


The chart shows we would use 2/0 copper (assuming solid copper, but it
won't be)

In a 100 feet of overhead run to a house, down the stack and through the
meter to the main panel, where the fuses or breakers are, not
considering the impedance of the overcurrent devices (that allegedly
cannot handle a fault this big) we come up a with a minimum copper
resistance of

200 feet (has to return) x 0.07793 x 10^-3 Ohms / foot (oh look ...your
old units too) = 0.015586 Ohms

Using 240 Vac as the fault supply (it won't be under a faulted
condition) the max fault current would be

240 Vac / 0.015586 Ohms = 15.4 kA.

Using a real transformer houses will have far less available fault current.


Now we havent figured in any of the other impedances (very generous)
and any approved O/C device in a panel these days is rated at 100kA.

Cite where 100kA is required.


Only problem with that is that many home service panels use breakers
with an AIR of only 10kA, not 100kA. (my old house, built in 2000 was
10kA, and my new one, built in 2010 is also 10kA, both perfectly correct
by code)

Here's are some modern service panels that come with 10k AIR breakers.
http://static.schneider-electric.us/...ad-centers.pdf

And how many homes in the utilities service area are even up to current
code? I'd bet many homes in many service areas have only 10kA AIR.

I agree that is very likely. One reason is that a higher rating is not
necessary.

(SquareD, if I remember right, has a rating of 20kA downstream from both
the main and branch circuit breaker.)

I doubt many Canadian house panels have fuse protection, or are
different from US panels with circuit breaker protection rated around 10kA.


The utility that is being ultra-conservative may have to consider that
older homes in their service area may not even support this.

Can you just imagine the hue and cry when some homeowners are told they
have to spend a couple hundred bucks to upgrade their service panel
because of changes in the utility's distribution?

daestrom

The interrupt rating required goes up with the service current rating.
For a house, the utility is not likely to have over 10,000kA available
fault current. The transformers become too large, many houses are
supplied with longer wires and higher resistance losses, and the system
is much less safe.

I believe it would take a rather massive amount of PV installations to
cause a problem. The PV installations would all have to be on the
secondary of the same utility transformer. The transformer is then not
likely to support the PV current back to the grid. If the fault current
is 20x the transformer full load current, and the PV current is equal to
the transformer full load current, the PV supply would increase the
fault current by about 5% (assuming the inverter doesn't shut down). If
there were too many PV installations the utility could put fewer houses
on a transformer. Seems like a problem that is not that hard to handle
for the utility, at least until PV generation becomes rather common.

--
bud--

On 4/12/2011 9:33 AM, Home Guy wrote:
g wrote:

Unless your invertors were set to operate at a slightly higher
output voltage. Even just a few volts differential between the
mains voltage and the invertor output would mean that you could
push current out into the grid, and by doing that raise the local
grid voltage slightly.

The grid can be seen as a pretty rigid beast. No small puny inverter
in the sub 1000kW class will much affect the grid voltage as a whole.
When voltage of the converter is attempted to be raised, current will
flow into the grid of course. The voltage increase will hardly be
measurable, as electrical characteristics of the grid will adjust
dynamically.

At any one time, there is a certain load on the grid as a whole. When
Mr. Homeowner adds 10Kw from some solar panels, some other power
generating systems connected to the grid will (have to) reduce their
output. As a result the voltage stays the same overall.

Here's the problem:

Many of the load devices you find in a typical home (primarily electric
motors that run cooling systems, air conditioners, fridges and freezers)
are not capable of regulating their input voltage.

So when a secondary electricity source comes on-line (like a small PV
system) then in order to push it's current into the local grid it will
have to *try* to raise it's output voltage in order to see some current
flow. It might only be a few volts, maybe less.

But does that mean there will be a measurable net reduction in the
current being supplied by the high-voltage substation for that corner of
the city?

Not if your typical load device in homes surround the PV system will
simply operate at a higher wattage.

The only sort of load that can effectively be regulated by a slight
increase in local grid voltage are electric heaters. When you raise
their input voltage slightly, they will put out more BTU of heat, and if
their heat output set-point doesn't change, then their operational duty
cycle will change slightly.

But in the case of an AC compressor, the fact that it might be getting a
slightly higher input voltage because a neighboring house is feeding PV
power into the local grid won't mean that the AC compressor will reduce
it's current consumption from the municipal utility supplier because of
the extra current coming from a neighbor's roof-top solar array. It
just means the motor will use BOTH sources of current and (I suppose)
run a little hotter but in the end not do any extra cooling work in the
process (it's rotational speed won't change).

Same theory would hold true for lighting (incandescent especially). If
you raise the input voltage, you'll get more light output - the bulb
will simply consume all the juice it would normally get from the utility
in addition to that being supplied by the neighborhood PV system.

The only way that a neighborhood PV system can actually suppliment
municipal utility power is when the PV system is wired up as a dedicated
sole supply source for a few select branch circuits. The way I see it,
you have to feed certain select loads 100% from a PV system (ie -
disconnect them from the municipal energy source) if you're going to
make a meaningful contribution to the supply-side of a municipal or
city-wide grid.

A devastating analysis.

I am sure when the utilities read it they will stop paralleling
generators, since that just causes the amount of electricity used to go
up from what would be used by isolated systems.

--
bud--

"bud--" wrote in message ...

On 4/11/2011 4:31 PM, daestrom wrote:
On 4/10/2011 22:12 PM, m II wrote:


"daestrom" wrote in message ...

On 4/6/2011 19:31 PM, m II wrote:
The fault capacity of a household main breaker or fuses is not an issue,
unless very old technology, like you.
One hundred feet of twisted triplex supply cable limits faults to well
within the fault tolerances.


Got some numbers/calculations to support that? Is that including the
next door neighbors with their PV installation?

daestrom

-------------------

Sure! Basic Ohms lawa and a wire resistance table

http://en.wikipedia.org/wiki/American_wire_gauge

A 200 ampere service running 240 Vac and only considering the straight
resistance of copper (many use AL outside conductors these days).
and considering the street transformer as an infinite current supply (0
Ohms impedance)

This is a fatal flaw in your argument. Transformers are not infinite
sources. A utility transformer might supply a fault current 20x the
rated current (for a "5% impedance" transformer). (While a transformer
will supply a fault current larger than the rated current that is not
likely with PV. PV is basically a constant current source.)


The chart shows we would use 2/0 copper (assuming solid copper, but it
won't be)

In a 100 feet of overhead run to a house, down the stack and through the
meter to the main panel, where the fuses or breakers are, not
considering the impedance of the overcurrent devices (that allegedly
cannot handle a fault this big) we come up a with a minimum copper
resistance of

200 feet (has to return) x 0.07793 x 10^-3 Ohms / foot (oh look ...your
old units too) = 0.015586 Ohms

Using 240 Vac as the fault supply (it won't be under a faulted
condition) the max fault current would be

240 Vac / 0.015586 Ohms = 15.4 kA.

Using a real transformer houses will have far less available fault current.


Now we havent figured in any of the other impedances (very generous)
and any approved O/C device in a panel these days is rated at 100kA.

Cite where 100kA is required.


Only problem with that is that many home service panels use breakers
with an AIR of only 10kA, not 100kA. (my old house, built in 2000 was
10kA, and my new one, built in 2010 is also 10kA, both perfectly correct
by code)

Here's are some modern service panels that come with 10k AIR breakers.
http://static.schneider-electric.us/...ad-centers.pdf

And how many homes in the utilities service area are even up to current
code? I'd bet many homes in many service areas have only 10kA AIR.

I agree that is very likely. One reason is that a higher rating is not
necessary.

(SquareD, if I remember right, has a rating of 20kA downstream from both
the main and branch circuit breaker.)

I doubt many Canadian house panels have fuse protection, or are
different from US panels with circuit breaker protection rated around 10kA.


The utility that is being ultra-conservative may have to consider that
older homes in their service area may not even support this.

Can you just imagine the hue and cry when some homeowners are told they
have to spend a couple hundred bucks to upgrade their service panel
because of changes in the utility's distribution?

daestrom

The interrupt rating required goes up with the service current rating.
For a house, the utility is not likely to have over 10,000kA available
fault current. The transformers become too large, many houses are
supplied with longer wires and higher resistance losses, and the system
is much less safe.

I believe it would take a rather massive amount of PV installations to
cause a problem. The PV installations would all have to be on the
secondary of the same utility transformer. The transformer is then not
likely to support the PV current back to the grid. If the fault current
is 20x the transformer full load current, and the PV current is equal to
the transformer full load current, the PV supply would increase the
fault current by about 5% (assuming the inverter doesn't shut down). If
there were too many PV installations the utility could put fewer houses
on a transformer. Seems like a problem that is not that hard to handle
for the utility, at least until PV generation becomes rather common.

--
bud--

-----------------
Perhaps re-read ( or just read ) the last few posts. Your objection is
mostly agreement with items already covered.

Can you cite the percent impedance of the transformers or the code rules
you discuss?




mike

"bud--" wrote in message ...

On 4/12/2011 9:33 AM, Home Guy wrote:
The only way that a neighborhood PV system can actually suppliment
municipal utility power is when the PV system is wired up as a dedicated
sole supply source for a few select branch circuits. The way I see it,
you have to feed certain select loads 100% from a PV system (ie -
disconnect them from the municipal energy source) if you're going to
make a meaningful contribution to the supply-side of a municipal or
city-wide grid.

A devastating analysis.

I am sure when the utilities read it they will stop paralleling
generators, since that just causes the amount of electricity used to go
up from what would be used by isolated systems.

------------------

Careful!
Sarcasm does not work well in a text medium, at all!

People cannot see your facial expression and people are never sure unless it
is totally ridiculous.

I agree with your point but it is made very poorly in a text only medium.



mike

"David Nebenzahl" wrote in message
s.com...
Is the spindle motor in your DVD player AC? How about the spindle motor on
your hard drive?

No magic there! Spindle motors simplyt substitute solid state switching for
mechanical commutation. Actually, what is fed to the windings of a spindle
motor (though you may "nictpick" by calling it pulsating DC) actually more
resembles 3-phase AC. In fact, the windings of a spindle motor are usually
connected in a wye or delta configuration, sound familiar?


You do agree that those are all examples of "rotating machinery", don't you?

I agree that spindle motors are examples of rotating machinery. I don't agree
that proves any particular point for you.


Vaughn

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Hash: SHA1



On 11-04-12 09:58 AM, m II wrote:

Nothing.

Forgery reported to nntp provider

mike






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On Apr 12, 3:08*pm, Home Guy wrote:
harry wrote:
And how many homes in the utilities service area are even up to
current code? *I'd bet many homes in many service areas have only
10kA AIR.

The utility that is being ultra-conservative may have to consider
that older homes in their service area may not even support this.

Can you just imagine the hue and cry when some homeowners are told
they have to spend a couple hundred bucks to upgrade their service
panel because of changes in the utility's distribution?

Small scale locally generated power makes no difference to these
problems. In fact it helps.

Our regional and municipal electricity distributors are not pointing the
finger at the capability or specs of residential service panels or
neighborhood distribution / stepdown transformers as the reason why they
won't let small-scale (less than 10kw) roof-top PV systems to connect to
the grid.

They are saying that the local sub-station doesn't have the "capability"
to allow for a handful (or perhaps even a single) small-scale PV systems
to be hooked up and they would need to "upgrade" the sub-station in some
way.

For more about this, see he

http://www.greenpowertalk.org/archiv...p/t-13885.html

And less relevant, he

http://www.canadianenergylaw.com/201...ricity/meterin...

All the arguments put forward here about why homeowner-operated PV
systems (with nameplate rating under 10kw) are not being allowed to
connect to the grid through their own bi-directional revenue meter have
not addressed the issue as to how the connection of such a PV system can
possibly affect or influence the operation of the regional municipal
sub-station supplying power (at 20 kv?) to the neighborhood in
question. *The sub-station is "insulated" from direct exposure to any
individual home by at least 1 step-down distribution transformer (in our
case, a ground-mounted distribution transformer supplying maybe 20 homes
- our electrical service runs underground - not on poles in our
neighborhood).

There may not yet even be a single residential PV system that's been
connected to the grid for the area being served by the sub-station in
question.

They lie. It's as simple as that.

On Apr 12, 3:33*pm, Home Guy wrote:
g wrote:
Unless your invertors were set to operate at a slightly higher
output voltage. *Even just a few volts differential between the
mains voltage and the invertor output would mean that you could
push current out into the grid, and by doing that raise the local
grid voltage slightly.

The grid can be seen as a pretty rigid beast. No small puny inverter
in the sub 1000kW class will much affect the grid voltage as a whole.
When voltage of the converter is attempted to be raised, current will
flow into the grid of course. The voltage increase will hardly be
measurable, as electrical characteristics of the grid will adjust
dynamically.

At any one time, there is a certain load on the grid as a whole. When
Mr. Homeowner adds 10Kw from some solar panels, some other power
generating systems connected to the grid will (have to) reduce their
output. As a result the voltage stays the same overall.

Here's the problem:

Many of the load devices you find in a typical home (primarily electric
motors that run cooling systems, air conditioners, fridges and freezers)
are not capable of regulating their input voltage.

So when a secondary electricity source comes on-line (like a small PV
system) then in order to push it's current into the local grid it will
have to *try* to raise it's output voltage in order to see some current
flow. *It might only be a few volts, maybe less.

But does that mean there will be a measurable net reduction in the
current being supplied by the high-voltage substation for that corner of
the city?

Not if your typical load device in homes surround the PV system will
simply operate at a higher wattage.

The only sort of load that can effectively be regulated by a slight
increase in local grid voltage are electric heaters. *When you raise
their input voltage slightly, they will put out more BTU of heat, and if
their heat output set-point doesn't change, then their operational duty
cycle will change slightly.

But in the case of an AC compressor, the fact that it might be getting a
slightly higher input voltage because a neighboring house is feeding PV
power into the local grid won't mean that the AC compressor will reduce
it's current consumption from the municipal utility supplier because of
the extra current coming from a neighbor's roof-top solar array. *It
just means the motor will use BOTH sources of current and (I suppose)
run a little hotter but in the end not do any extra cooling work in the
process (it's rotational speed won't change).

Same theory would hold true for lighting (incandescent especially). *If
you raise the input voltage, you'll get more light output - the bulb
will simply consume all the juice it would normally get from the utility
in addition to that being supplied by the neighborhood PV system.

The only way that a neighborhood PV system can actually suppliment
municipal utility power is when the PV system is wired up as a dedicated
sole supply source for a few select branch circuits. *The way I see it,
you have to feed certain select loads 100% from a PV system (ie -
disconnect them from the municipal energy source) if you're going to
make a meaningful contribution to the supply-side of a municipal or
city-wide grid.- Hide quoted text -

- Show quoted text -

I think you need to go back to school.

On 11/04/2011 23:17, harry wrote:
On Apr 11, 8:01 pm, David wrote:


You don't "push" electricity from your solar installation into the grid
by raising the voltage, as someone here postulated. It just don't work
that way.



Yes it does. Electrical current flows from a point of higher
potential to a lower point. The very first thing you learn. Ohm's Law.

So, you don't increase current by raising the voltage, but you increase
current by having a higher potential.

Now, difference in potential is voltage?

On Apr 12, 4:44*pm, bud-- wrote:
On 4/11/2011 4:31 PM, daestrom wrote:





On 4/10/2011 22:12 PM, m II wrote:

"daestrom" wrote in ...

On 4/6/2011 19:31 PM, m II wrote:
The fault capacity of a household main breaker or fuses is not an issue,
unless very old technology, like you.
One hundred feet of twisted triplex supply cable limits faults to well
within the fault tolerances.

Got some numbers/calculations to support that? Is that including the
next door neighbors with their PV installation?

daestrom

-------------------

Sure! Basic Ohms lawa and a wire resistance table

http://en.wikipedia.org/wiki/American_wire_gauge

A 200 ampere service running 240 Vac and only considering the straight
resistance of copper (many use AL outside conductors these days).
and considering the street transformer as an infinite current supply (0
Ohms impedance)

This is a fatal flaw in your argument. Transformers are not infinite
sources. A utility transformer might supply a fault current 20x the
rated current (for a "5% impedance" transformer). (While a transformer
will supply a fault current larger than the rated current that is not
likely with PV. PV is basically a constant current source.)







The chart shows we would use 2/0 copper (assuming solid copper, but it
won't be)

In a 100 feet of overhead run to a house, down the stack and through the
meter to the main panel, where the fuses or breakers are, not
considering the impedance of the overcurrent devices (that allegedly
cannot handle a fault this big) we come up a with a minimum copper
resistance of

200 feet (has to return) x 0.07793 x 10^-3 Ohms / foot (oh look ...your
old units too) = 0.015586 Ohms

Using 240 Vac as the fault supply (it won't be under a faulted
condition) the max fault current would be

240 Vac / 0.015586 Ohms = 15.4 kA.

Using a real transformer houses will have far less available fault current.

On Apr 12, 5:30*pm, "vaughn" wrote:
"David Nebenzahl" wrote in message

s.com...

Is the spindle motor in your DVD player AC? How about the spindle motor on
your hard drive?

No magic there! *Spindle motors simplyt substitute solid state switching for
mechanical commutation. *Actually, what is fed to the windings of a spindle
motor (though you may "nictpick" by calling it pulsating DC) actually more
resembles 3-phase AC. *In fact, the windings of a spindle motor are usually
connected in a wye or delta configuration, sound familiar?



You do agree that those are all examples of "rotating machinery", don't you?

I agree that spindle motors are examples of rotating machinery. *I don't agree
that proves any particular point for you.

Vaughn

Exactly so. Every single electric motor without exception runs on AC.
The correct term for the above is synchronous motors. Stepper motors
are a similar sort of thing for other applications.
http://en.wikipedia.org/wiki/Synchronous_motor#Uses
http://en.wikipedia.org/wiki/Stepper_motor

In days of yore "DC motors" were used where speed control was
neccessary.
The AC was created by the armature and brushes.
Changing frequencies was not cheaply possible by any other way.
Nowadays it is very easily possible and "DC motors" have virtually
disappeared.