Toshiba TV29C90 problem; Image fades to black...

In alt.engineering.electrical Michael A. Terrell <mike.terrell@earthlink.net> wrote:

| The central air kicks on without my lights dimming, and I am in North
| Central Florica.

I bet it's on its own branch circuit, too.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
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| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

[Forrest]

<cuhulin@webtv.net> wrote in message
news:25213-4824F7F6-353@storefull-3254.bay.webtv.net...

My little Blue Heeler Australian Cattle Dog, www.cattledog.com
www.acdca.org she goes absolutely NUTS! about flashlights and similar
portable lights, she owns the couch.I run one of my flashlights around
in circles on the floor or out in the front yard in the evenings, she
gets lots of excersize chaseing that light around and around in
clockwise circles.I reckon she is a Republican right winger like I
am.She can't run around in counter clockwise circles, she loses her
balance.
cuhulin

We have an Irish Setter that does the same thing with any kind of light or
reflection. I wish we had never gotten him started doing that. Can't have
him in the kitchen while cooking or washing pots and pans. He almost climbs
the walls trying to get the reflections. Now he stands on the concrete patio
looking, whining and pawing at birds' shadows from the overhead wires. Maybe
it's just because he's crazy as an outhouse rat to begin with.

 

In alt.engineering.electrical Michael A. Terrell <mike.terrell@earthlink.net> wrote:
| phil-news-nospam@ipal.net wrote:
|>
|> In alt.engineering.electrical Michael A. Terrell <mike.terrell@earthlink.net> wrote:
|>
|> | The central air kicks on without my lights dimming, and I am in North
|> | Central Florica.
|>
|> I bet it's on its own branch circuit, too.
|
|
| So what? The meter is on a pole on one side of the driveway ( two
| feet from the property line, because Progress Energy does not allow
| drops to cross a driveway anymore.), and an outdoor breaker box is on
| the remaining four foot stump of the old pole on the other side of the
| paved drive, about 40 feet away. The 60 A breaker for the AC is in that
| box, along with the 100 A main breaker that is used as a disconnect for
| the house. That box is over 125 feet from the pole pig, on a 150 A
| service. That box also feeds another underground line to the laundry
| building,, and well pump. The main breaker box for the house is another
| 20 feet from the outdoor box. Now, tell me how it can have no effect on
| the line voltage. I still see very little flickering, usually only on
| hot summer days when everyone in the subdivision is using the AC and
| their kitchen stoves at the same time. That is usually followed by a
| blown 60 A fuse in the 7200 volt line, feeding my street.

If it were not on its own branch circuit, that would (in addition to being
a code violation) more likely cause other stuff (whatever else is on the
same circuit) to experience dimming. The fact that it is onis own branch
circuit doesn't mean there isn't a big voltage drop. But only the A/C would
be getting it, and it wouldn't matter (much).

It can have no (or very little that cannot be noticed) effect on the line
voltage because you have good wiring and the transformer has a high enough
capacity and low enough impedance. This is stuff you know.

Blowing a 60 amp fuse at 7200 volts is not a small neighborhood.

I can understand them not wanting to go overheard over a driveway. RVs can
be a fun place for kids to climb on (even if terribly unsafe). Or they can
catch fire (I've seen that happen and it _was_ a case of a service drop over
a driveway that faulted when the insulation melted off).

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

In alt.engineering.electrical Michael A. Terrell <mike.terrell@earthlink.net> wrote:
| phil-news-nospam@ipal.net wrote:
|>
|> In alt.engineering.electrical Michael A. Terrell <mike.terrell@earthlink.net> wrote:
|> | phil-news-nospam@ipal.net wrote:
|> |>
|> |> In alt.engineering.electrical Michael A. Terrell <mike.terrell@earthlink.net> wrote:
|> |>
|> |> | The central air kicks on without my lights dimming, and I am in North
|> |> | Central Florica.
|> |>
|> |> I bet it's on its own branch circuit, too.
|> |
|> |
|> | So what? The meter is on a pole on one side of the driveway ( two
|> | feet from the property line, because Progress Energy does not allow
|> | drops to cross a driveway anymore.), and an outdoor breaker box is on
|> | the remaining four foot stump of the old pole on the other side of the
|> | paved drive, about 40 feet away. The 60 A breaker for the AC is in that
|> | box, along with the 100 A main breaker that is used as a disconnect for
|> | the house. That box is over 125 feet from the pole pig, on a 150 A
|> | service. That box also feeds another underground line to the laundry
|> | building,, and well pump. The main breaker box for the house is another
|> | 20 feet from the outdoor box. Now, tell me how it can have no effect on
|> | the line voltage. I still see very little flickering, usually only on
|> | hot summer days when everyone in the subdivision is using the AC and
|> | their kitchen stoves at the same time. That is usually followed by a
|> | blown 60 A fuse in the 7200 volt line, feeding my street.
|>
|> If it were not on its own branch circuit, that would (in addition to being
|> a code violation) more likely cause other stuff (whatever else is on the
|> same circuit) to experience dimming. The fact that it is onis own branch
|> circuit doesn't mean there isn't a big voltage drop. But only the A/C would
|> be getting it, and it wouldn't matter (much).
|>
|> It can have no (or very little that cannot be noticed) effect on the line
|> voltage because you have good wiring and the transformer has a high enough
|> capacity and low enough impedance. This is stuff you know.
|>
|> Blowing a 60 amp fuse at 7200 volts is not a small neighborhood.
|
|
| 48 lots, 47 with homes. That gives 7200*60/240 or 1800 A @ 240 V for
| 47 homes gives an average 38.29 A per home which is the reason that fuse
| can blow more than once a week, along with it's explosive discharge that
| sounds like a shotgun every time it blows.

Yup, big neighborhood. It wouldn't take much after 47 home central A/C's
are running to go over the fuse rating. Any guess what the curve on that
fuse is? E.g. how long can you go at 105%? 125%?

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

[Mark D. Zacharias]

<tx7123@yahoo.com> wrote in message
news:b2fdab22-8f8c-4c93-a720-d79cc0fe3bff@i76g2000hsf.googlegroups.com...
On May 3, 5:19 pm, "Mark D. Zacharias" <mzachar...@nonsense.net>
wrote:

Hi ,

<SNIP>

I decided to lift the board and look at the solder for the device
sanyo 313e.
Before I could do anything the V shaped metal (heatsink?) attached >to
the
device just fell off. The plastic screw holding it had just cracked >in
half.
There also is a thin piece of plastic between the device and the
heatsink.
I'm assuming that they do want the device to touch the metal.
I could not find a another plastic screw, so I use a metal one with
an
insulating washer. I hope that is ok. Why does the device need to >be
insulated from the metal heatsink. Is it strictly pecautionary, in
case
the heatsink comes in contact with something else. Would it be ok
to put some cpu grease between the device and the plastic >insulator?
Anyway after all this the solder looked ok, so I did not resolder.
I wonder if my problem all along was that the heatsink
was just hanging on by a thread.
Anyway it seems to work ok. I'll run it for a while with the case
open
as a precaution.

Thanks

If the solder is really OK, which I doubt. Then the transistor is failing.
On this TO-220 case transistor this most commonly happens from a
base-emitter junction opening up internally.

If you were to look very closely at the solder connections ( I recommend a
magnifying glass) I believe you will see the ring-cracks around the
transistor leads.

In this particular case the heat sink has no other electrical connection,
but you are still going to need another screw and nut. Another mica
insulator and some silicon grease would be good, although as I say, in this
case I think you could dispense with the mica.

Alternatively you could use a newer style TO-220PL plastic case transistor
such as a 2SC4793 which requires no insulator.

It's unfortunate in a way that your skills and experience don't seem to
quite be up to the task. I don't say that as a put-down, but this whole
thing should have been over long ago.

If you decide to replace the transistor, you'll need a source for the part,
and most suppliers have 15.00 to 20.00 minimum orders.

You might consider OEQuotefix to fix your problem with Outlook Express
making messy looking posts. It's a free download.


Mark Z.

 

[Mark D. Zacharias]

<tx7123@yahoo.com> wrote in message
news:b2fdab22-8f8c-4c93-a720-d79cc0fe3bff@i76g2000hsf.googlegroups.com...
On May 3, 5:19 pm, "Mark D. Zacharias" <mzachar...@nonsense.net>
wrote:

Hi ,

<SNIP>

I decided to lift the board and look at the solder for the device
sanyo 313e.
Before I could do anything the V shaped metal (heatsink?) attached >to
the
device just fell off. The plastic screw holding it had just cracked >in
half.
There also is a thin piece of plastic between the device and the
heatsink.
I'm assuming that they do want the device to touch the metal.
I could not find a another plastic screw, so I use a metal one with
an
insulating washer. I hope that is ok. Why does the device need to >be
insulated from the metal heatsink. Is it strictly pecautionary, in
case
the heatsink comes in contact with something else. Would it be ok
to put some cpu grease between the device and the plastic >insulator?
Anyway after all this the solder looked ok, so I did not resolder.
I wonder if my problem all along was that the heatsink
was just hanging on by a thread.
Anyway it seems to work ok. I'll run it for a while with the case
open
as a precaution.

Thanks

If the solder is really OK, which I doubt. Then the transistor is failing.
On this TO-220 case transistor this most commonly happens from a
base-emitter junction opening up internally.

If you were to look very closely at the solder connections ( I recommend a
magnifying glass) I believe you will see the ring-cracks around the
transistor leads.

In this particular case the heat sink has no other electrical connection,
but you are still going to need another screw and nut. Another mica
insulator and some silicon grease would be good, although as I say, in this
case I think you could dispense with the mica.

Alternatively you could use a newer style TO-220PL plastic case transistor
such as a 2SC4793 which requires no insulator.

It's unfortunate in a way that your skills and experience don't seem to
quite be up to the task. I don't say that as a put-down, but this whole
thing should have been over long ago.

If you decide to replace the transistor, you'll need a source for the part,
and most suppliers have 15.00 to 20.00 minimum orders.

You might consider OEQuotefix to fix your problem with Outlook Express
making messy looking posts. It's a free download.


Mark Z.

 

[Tzortzakakis Dimitrios]

? "Michael A. Terrell" <mike.terrell@earthlink.net> ?????? ??? ??????
news:KridndAr1fGpnLvVnZ2dnUVZ_jSdnZ2d@earthlink.com...

Tzortzakakis Dimitrios wrote:

The regulation, at least in Europe, is done at 150/15 kV substations and
at
the HV side of the transformers, thus at 150 kV. Typical current for 2 x
25
MVA transformers is 150 A, 150 kV and of course secondary at 15 kV, 1500
A.
The regulation is done automatically with tap changers, live. The local
transformers at your neighborhood are fixed tap, 15 kV (they intend to
change everything to 20 kV).


So they have developed 100% efficient transformers?

.net/ISP.htm
Of course not These are approximate figures (like the 21 kV 10 kA

alternator, which in fact is 9823 A 21200 volts or whatever). But the
efficiency of large transformers or transmission lines, when they operate at
optimum is 99%.




--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr

 

[Tzortzakakis Dimitrios]

? "Michael A. Terrell" <mike.terrell@earthlink.net> ?????? ??? ??????
news:KridndAr1fGpnLvVnZ2dnUVZ_jSdnZ2d@earthlink.com...

Tzortzakakis Dimitrios wrote:

The regulation, at least in Europe, is done at 150/15 kV substations and
at
the HV side of the transformers, thus at 150 kV. Typical current for 2 x
25
MVA transformers is 150 A, 150 kV and of course secondary at 15 kV, 1500
A.
The regulation is done automatically with tap changers, live. The local
transformers at your neighborhood are fixed tap, 15 kV (they intend to
change everything to 20 kV).


So they have developed 100% efficient transformers?

.net/ISP.htm
Of course not These are approximate figures (like the 21 kV 10 kA

alternator, which in fact is 9823 A 21200 volts or whatever). But the
efficiency of large transformers or transmission lines, when they operate at
optimum is 99%.




--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr

 

[William Sommerwerck]

There is a good chance that charging the batteries externally
won't do a thing but then you've not lost anything just giving it
a try.

I don't know if lead-acid gel cells are susceptible to sulfation
as are liquid-filled cells but that is a usual cause of failure from
liquid batteries being stored without a charge being maintained.

I don't want to discourage the OP from trying to recharge the battery -- be
sure to cover them with something thick and heavy, in case they rupture or
explode (I'm not trying to be funny) -- but when I recently pulled out a
Coleman fluorescent lantern powered by an E640 gel battery, I found it dead.
The several-years' lack of charging had allowed the battery to die.
Lead-acid batteries are fragile beasts.

 

[William Sommerwerck]

"Meat Plow" <meat@petitmorte.net> wrote in message
news:1s3vhl.1se.19.1@news.alt.net...

I don't want the OP to blow himself up either but a small current
applied long enough to boost the voltage up to where the APC will
charge them is fairly innocuous. The Smart UPS 700 was a very
popular small server backup solution several years ago and I have
experimented with them and their batteries without causing death
or dismemberment. And I would tend to disagree with you regarding
the fragility of lead-acid batteries in general. They are exposed to
some pretty harsh environmental conditions every day in automotive
and industrial use.

They're about the most-fragile battery I know of, and this is an excellent
example.

What other kind of rechargeable battery can be destroyed by running it all
the way down -- just ONCE? This happened to me about 15 years ago with a
lead-acid battery pack for a Sony Discman. I carelessly let it completely
discharge -- and it was gone. I was out $30.

This is not true of nicads or NiMH cells. I don't know whether it's true of
lithium-ion or lithium-polymer cells, about which there's a lot of myth.

 

[William Sommerwerck]

"w_tom" <w_tom1@usa.net> wrote in message
news:f00df652-9f41-49f5-afc0-f9eb5164bb8f@l17g2000pri.googlegroups.com...
On May 11, 3:17 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

What other kind of rechargeable battery can be destroyed by running it all
the way down -- just ONCE?

Battteries are cells in series. If the battery pack discharges too
deeply, then current output by most cells can reverse charge the
weakest cell. Sometimes this can result in a short inside that one
cell. The entire battery is bad because too much discharging has
reverse charged and destroyed one cell. Its rare. But is does
happen.

That isn't the issue here. It's the fact that lead-acid cells can be
destroyed by a single full discharge.

By the way, I've seen primary alkaline and lithium cells reverse-charged.

 

[William Sommerwerck]

"w_tom" <w_tom1@usa.net> wrote in message
news:f00df652-9f41-49f5-afc0-f9eb5164bb8f@l17g2000pri.googlegroups.com...
On May 11, 3:17 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

What other kind of rechargeable battery can be destroyed by running it all
the way down -- just ONCE?

Battteries are cells in series. If the battery pack discharges too
deeply, then current output by most cells can reverse charge the
weakest cell. Sometimes this can result in a short inside that one
cell. The entire battery is bad because too much discharging has
reverse charged and destroyed one cell. Its rare. But is does
happen.

That isn't the issue here. It's the fact that lead-acid cells can be
destroyed by a single full discharge.

By the way, I've seen primary alkaline and lithium cells reverse-charged.

 

[Mark D. Zacharias]

<tx7123@yahoo.com> wrote in message
news:89bc8f04-d26f-4237-8b8a-3f1495b191b6@f63g2000hsf.googlegroups.com...
On May 11, 9:07 am, "Mark D. Zacharias" <mzachar...@nonsense.net>
wrote:

tx7...@yahoo.com> wrote in message

news:b2fdab22-8f8c-4c93-a720-d79cc0fe3bff@i76g2000hsf.googlegroups.com...
On May 3, 5:19 pm, "Mark D. Zacharias" <mzachar...@nonsense.net
wrote:

Hi ,

SNIP

I decided to lift the board and look at the solder for the device



sanyo 313e.
Before I could do anything the V shaped metal (heatsink?) attached >to
the
device just fell off. The plastic screw holding it had just cracked >in
half.
There also is a thin piece of plastic between the device and the
heatsink.
I'm assuming that they do want the device to touch the metal.
I could not find a another plastic screw, so I use a metal one with
an
insulating washer. I hope that is ok. Why does the device need to >be
insulated from the metal heatsink. Is it strictly pecautionary, in
case
the heatsink comes in contact with something else. Would it be ok
to put some cpu grease between the device and the plastic >insulator?
Anyway after all this the solder looked ok, so I did not resolder.
I wonder if my problem all along was that the heatsink
was just hanging on by a thread.

Anyway it seems to work ok. I'll run it for a while with the case>open

as a precaution.

Thanks

If the solder is really OK, which I doubt. Then the transistor is failing.
On this TO-220 case transistor this most commonly happens from a
base-emitter junction opening up internally.

If you were to look very closely at the solder connections ( I recommend a
magnifying glass) I believe you will see the ring-cracks around the
transistor leads.

In this particular case the heat sink has no other electrical connection,
but you are still going to need another screw and nut. Another mica
insulator and some silicon grease would be good, although as I say, in
this
case I think you could dispense with the mica.

Alternatively you could use a newer style TO-220PL plastic case transistor
such as a 2SC4793 which requires no insulator.

It's unfortunate in a way that your skills and experience don't seem to
quite be up to the task. I don't say that as a put-down, but this whole
thing should have been over long ago.

If you decide to replace the transistor, you'll need a source for the
part,
and most suppliers have 15.00 to 20.00 minimum orders.

You might consider OEQuotefix to fix your problem with Outlook Express
making messy looking posts. It's a free download.

Mark Z.- Hide quoted text -

- Show quoted text -

No need to be nasty.
The solder looked ok to me.
The board is very old, so the plan is to proceed cautiously.
I have attached the device properly to the heatsink.
If the problem recurrs, I will reheat the solder joints.
If that does not solve the problem then I will replace the device.
I'm assuming that a 2sd613 will be an adequate replacement, correct?

*****************************
A 2SD 613 would be fine.

I'm not sure why the > marks aren't showing in the quoted sections, I had to
add them manually last time.

I don't feel I was being nasty before, even said so:

I don't say that as a put-down, but this whole
thing should have been over long ago.

I was watching as several other responders were telling you to replace the
transistor and a lot of back-and-forth when as I say this coulda / shoulda
been over with long ago.

mz

 

[Michael Kennedy]

"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
news:4f99e77a89dave@davenoise.co.uk...

In article <481c590e$0$30484$4c368faf@roadrunner.com>,
"Blattus Slafaly ? (3) ź " <boobooililililil@roadrunner.com> wrote:
A power supply is a power supply.

No they're not. Things like regulation and short circuit protection can
vary enormously.

The cheapest one will do. I have good
luck with $18.00 power supplies. They either work or they don't.

And a cheap SMPS with cheap caps is not likely to last long. An analogue
one with a poor transformer - the expensive part.

People
who pay $150 or $200 for a power supply are crazy.

It would depend on the rating of it. $200 would be crazy for a 1 amp one -
but not for a decent bench supply.

I've bought the
cheapest for decades. It don't have to last 200 years, I won't live that
long and it will be obsolete in a couple years anyway.

What becomes obsolete in a power supply?

Good question.. Maybe he is talking about a ATX PC power supply? All of my
AT power supplies are unfortunately obsolete, at least for use in modern
computers.

 

[Michael Kennedy]

"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
news:4f99e77a89dave@davenoise.co.uk...

In article <481c590e$0$30484$4c368faf@roadrunner.com>,
"Blattus Slafaly ? (3) ź " <boobooililililil@roadrunner.com> wrote:
A power supply is a power supply.

No they're not. Things like regulation and short circuit protection can
vary enormously.

The cheapest one will do. I have good
luck with $18.00 power supplies. They either work or they don't.

And a cheap SMPS with cheap caps is not likely to last long. An analogue
one with a poor transformer - the expensive part.

People
who pay $150 or $200 for a power supply are crazy.

It would depend on the rating of it. $200 would be crazy for a 1 amp one -
but not for a decent bench supply.

I've bought the
cheapest for decades. It don't have to last 200 years, I won't live that
long and it will be obsolete in a couple years anyway.

What becomes obsolete in a power supply?

Good question.. Maybe he is talking about a ATX PC power supply? All of my
AT power supplies are unfortunately obsolete, at least for use in modern
computers.

 

[Dave Plowman (News)]

In article <dIqdnb7olaJ_Y7rVnZ2dnUVZ_rzinZ2d@comcast.com>,
Michael Kennedy <Mikek400@remthis.comcast.net> wrote:

What becomes obsolete in a power supply?

Good question.. Maybe he is talking about a ATX PC power supply? All of
my AT power supplies are unfortunately obsolete, at least for use in
modern computers.

Indeed - but the OP talked about a 30v 10A CVCC PS. Not that I know what
CVCC is - Google suggests it's the Cuckmere Valley Canoe Club. Perhaps
they use some form of electrolysis to reduce friction? ;-)

--
*Growing old is inevitable, growing up is optional

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Dave Plowman (News)]

In article <dIqdnb7olaJ_Y7rVnZ2dnUVZ_rzinZ2d@comcast.com>,
Michael Kennedy <Mikek400@remthis.comcast.net> wrote:

What becomes obsolete in a power supply?

Good question.. Maybe he is talking about a ATX PC power supply? All of
my AT power supplies are unfortunately obsolete, at least for use in
modern computers.

Indeed - but the OP talked about a 30v 10A CVCC PS. Not that I know what
CVCC is - Google suggests it's the Cuckmere Valley Canoe Club. Perhaps
they use some form of electrolysis to reduce friction? ;-)

--
*Growing old is inevitable, growing up is optional

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[William Sommerwerck]

"w_tom" <w_tom1@usa.net> wrote in message
news:a11ae4a9-bf83-41fe-b42b-9468650e9566@q27g2000prf.googlegroups.com...
On May 11, 8:11 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

That isn't the issue here. It's the fact that lead-acid cells can be
destroyed by a single full discharge.

The point is that any battery can be harmed by over discharging.

No, the point is that lead-acid cells are especially susceptible to being
damaged. I've never had this happen with a nickel-cadmium battery.

 

[William Sommerwerck]

"w_tom" <w_tom1@usa.net> wrote in message
news:a11ae4a9-bf83-41fe-b42b-9468650e9566@q27g2000prf.googlegroups.com...
On May 11, 8:11 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

That isn't the issue here. It's the fact that lead-acid cells can be
destroyed by a single full discharge.

The point is that any battery can be harmed by over discharging.

No, the point is that lead-acid cells are especially susceptible to being
damaged. I've never had this happen with a nickel-cadmium battery.

 

[Tzortzakakis Dimitrios]

? "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> ?????? ??? ??????
news:482725ae$0$30509$4c368faf@roadrunner.com...

"Tzortzakakis Dimitrios" <noone@nospam.void> wrote in message
news:g04cc6$edo$1@mouse.otenet.gr...

? "Andrew Gabriel" <andrew@cucumber.demon.co.uk> ?????? ??? ??????
news:48246da4$0$657$5a6aecb4@news.aaisp.net.uk...
snip
The transformers are small in comparison, which gives poor
regulation in comparison (and as I said before, it's the
regulation at 120V which is the primary concern -- regulation
of 240V across 2 hots doesn't matter much for typical US 240V
loads).
The regulation, at least in Europe, is done at 150/15 kV substations and
at the HV side of the transformers, thus at 150 kV. Typical current for 2
x 25 MVA transformers is 150 A, 150 kV and of course secondary at 15 kV,
1500 A. The regulation is done automatically with tap changers, live. The
local transformers at your neighborhood are fixed tap, 15 kV (they intend
to change everything to 20 kV).



You're confusing two uses of the term 'regulation'. Tap changers and
voltage regulators actively sense the terminal voltage and adjust
'something' to maintain the voltage within some design limit. That's a
'regulator' and provides 'regulation' of the sensed voltage.

I know that, but it was a temptation to post this
But 'regulation' also is a term used to describe the inherent voltage drop
in some devices. For example, if you review DC generators, you'll find
that simple shunt-wound generators have fairly good 'regulation' and their
output voltage only drops a few percent from no-load to full-load when
supplied with a fixed field. A cumulatively-compound DC generator (which
has a series field and a shunt field), can have a nearly flat voltage
curve from no-load to full-load with just a fixed shunt excitation, or
even have a voltage rise depending on the degree of compounding. (of
course, an active voltage regulator can counteract whatever inherent
regulation a machine may have)

A shame that Tesla won the infamous "battle" and we don't have DC:-() But

then, we would be having a power plant at each neighborhood, instead of the
300 MW ones.

In the case of simple fixed-tap transformers, the term 'regulation' can be
used to describe how much the output terminal voltage changes from no-load
to full-load if the primary voltage is held constant. This use is less
than perfect as it is much better to use the transformer's impedance along
with the load's power factor to get a more precise answer.

In the US, voltage regulation is accomplished with load-tap-changers,
capacitor banks, and other 'voltage support services'.
We have here capacitor banks, too, connected at the LV side of the

substation, 15 kV line-to-line voltage.
But just like in

Europe, it is done at the substation or higher level and not done at the
typical distribution transformer. There are exceptions for rural areas
though where the line length of the primary leads to some issues.

daestrom
P.S. In the US, a 'tap-changer' may be built for either for unloaded or
loaded operation. The 'unloaded' type can not be stepped to another tap
while there is load on the unit (although it can still be energized).
It's switch contacts cannot interrupt load though, so if you try to move
it while loaded, you can burn up the tap-changer. The classic
'load-tap-changer' is actually several switches that are controlled in a
precise sequence to shift the load from one tap of the transformer to
another while not interrupting the load current.

P.P.S. Load tap changers typically have a significant time-delay built
into the controls so they do not 'hunt' or respond to short drops in
voltage such as starting a large load. 15 seconds to several minutes is
typical. So even with load-tap-changers, starting a single load that is a
high percentage of the system capacity will *still* result in a voltage
dip.

Yeah, the ones we have here are automatic, live and even have a shaft for

manual control.

I know, I know, my answer was a bit provocative And of course there are

DC regulators.... You're talking about DC generators;the one a 300 MW uses
for excitation is 220 V, 1000 A DC and probably shunt field. I have seen
here in some machine shops the old type welding generator, which is a 3
phase induction motor coupled to (usually) a compound field DC generator,
which provides the welding current. The modern ones are, maybe, not larger
than a shoe box and powered by a higher wattage 230 V 16 A receptacle.
(Usual receptacles are 230 V 10 A;16 A for washing machines, dryers and the
like).



--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr