Toshiba TV29C90 problem; Image fades to black...

In sci.electronics.repair jakdedert <jakdedert@bellsouth.net> wrote:

I'm a little confused about a 230 volt circuit. In what part of the
world does the utility supply 230v?

Continental Europe used to have 220 volts (before that it was 127 volts in
some places), the UK used to have 240 volts. Nowadays, the common voltage
is 230 volts -10% +6%.

--
Met vriendelijke groet,

Maarten Bakker.

 

[isw]

In article <MPG.22927b2a5c31d25798969d@news.bright.net>,
Ol' Duffer <nospam@onme.com> wrote:

In article <5apg241m4gkpcuhsje4gbbiqabp6q9u0j2@4ax.com>,
markrrivet@verizon.net says...
What are the benefits of using a permanent magnet for a coil core.
I recently came across a design for a switching power supply that used
magnets as cores for the inductor. I have never heard of such a thing,
except maybe in speakers.

If there is DC current flowing in the coil, it reduces the amount of
flux "swing" that can happen without saturating the core. Or looking
at it from another angle, you need a physically larger (more $$) core
to do the same AC work if it is also carrying DC. Using a permanent
magnet to counteract the DC flux allows a smaller (cheaper) part to
be used. Used to see these in the vertical section of TV's in the
days before power IC's.

I suspect it was the horizontal, not the vertical, circuit, and its
purpose is to provide two different inductances, one for "positive"
currents, and a different one for "negative" currents. Those are used to
provide linearity correction.

Isaac

 

[isw]

In article <MPG.22927b2a5c31d25798969d@news.bright.net>,
Ol' Duffer <nospam@onme.com> wrote:

In article <5apg241m4gkpcuhsje4gbbiqabp6q9u0j2@4ax.com>,
markrrivet@verizon.net says...
What are the benefits of using a permanent magnet for a coil core.
I recently came across a design for a switching power supply that used
magnets as cores for the inductor. I have never heard of such a thing,
except maybe in speakers.

If there is DC current flowing in the coil, it reduces the amount of
flux "swing" that can happen without saturating the core. Or looking
at it from another angle, you need a physically larger (more $$) core
to do the same AC work if it is also carrying DC. Using a permanent
magnet to counteract the DC flux allows a smaller (cheaper) part to
be used. Used to see these in the vertical section of TV's in the
days before power IC's.

I suspect it was the horizontal, not the vertical, circuit, and its
purpose is to provide two different inductances, one for "positive"
currents, and a different one for "negative" currents. Those are used to
provide linearity correction.

Isaac

 

In alt.engineering.electrical James Sweet <jamessweet1@trashmail.net> wrote:
|
| phil-news-nospam@ipal.net wrote:
|> In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void> wrote:
|>
|> | 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.
|>
|> And the latter make easy terrorism targets, too.
|>
|>
|> | 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).
|>
|> You don't use 400 V for anything heavy duty like an oven?
|>
|
|
| In North America, 240V 50A is pretty standard for ovens, some are 40A,
| clothes dryers are 30A, most other stuff plugs into a 15A 120V receptacle.

But we don't have an easy option for any higher voltage. In many parts of
Europe, three phase 400/230V is delivered to homes. Then using 400V, either
2 lines or all 3 lines, is an option.

--
|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 James Sweet <jamessweet1@trashmail.net> wrote:
|
| phil-news-nospam@ipal.net wrote:
|> In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void> wrote:
|>
|> | 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.
|>
|> And the latter make easy terrorism targets, too.
|>
|>
|> | 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).
|>
|> You don't use 400 V for anything heavy duty like an oven?
|>
|
|
| In North America, 240V 50A is pretty standard for ovens, some are 40A,
| clothes dryers are 30A, most other stuff plugs into a 15A 120V receptacle.

But we don't have an easy option for any higher voltage. In many parts of
Europe, three phase 400/230V is delivered to homes. Then using 400V, either
2 lines or all 3 lines, is an option.

--
|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 daestrom <daestrom@no_spam_heretwcny.rr.com> wrote:
|
| <phil-news-nospam@ipal.net> wrote in message
| news:g0a7ts1t0c@news5.newsguy.com...
|> In alt.engineering.electrical Michael Moroney
|> <moroney@world.std.spaamtrap.com> wrote:
|>
|> | Are the load tap generators configured make-before-break?
|> | Break-before-make would mean a (very short) power outage every
|> activation
|> | but make-before-break would mean a momentarily short-circuited winding
|> and
|> | the break would involve interrupting a large short circuit current.
|>
|> I wonder how much regulation could be managed through the use of variable
|> leakage inductance in the transformer windings.
|>
|
| I suppose you could, but increasing leakage inductance means you're
| increasing losses aren't you? Just a percent or two on a unit rated for 250
| MVA can be too much to tolerate.

Isn't it just inductance in series? Shouldn't that just be a phase shift as
seen from the primary side?

--
|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 daestrom <daestrom@no_spam_heretwcny.rr.com> wrote:
|
| <phil-news-nospam@ipal.net> wrote in message
| news:g0a7ts1t0c@news5.newsguy.com...
|> In alt.engineering.electrical Michael Moroney
|> <moroney@world.std.spaamtrap.com> wrote:
|>
|> | Are the load tap generators configured make-before-break?
|> | Break-before-make would mean a (very short) power outage every
|> activation
|> | but make-before-break would mean a momentarily short-circuited winding
|> and
|> | the break would involve interrupting a large short circuit current.
|>
|> I wonder how much regulation could be managed through the use of variable
|> leakage inductance in the transformer windings.
|>
|
| I suppose you could, but increasing leakage inductance means you're
| increasing losses aren't you? Just a percent or two on a unit rated for 250
| MVA can be too much to tolerate.

Isn't it just inductance in series? Shouldn't that just be a phase shift as
seen from the primary side?

--
|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) |

 

[Don Kelly]

----------------------------
"Michael Moroney" <moroney@world.std.spaamtrap.com> wrote in message
news:g0a1o5$bcq$1@pcls6.std.com...

"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> writes:


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.

Are the load tap generators configured make-before-break?
Break-before-make would mean a (very short) power outage every activation
but make-before-break would mean a momentarily short-circuited winding and
the break would involve interrupting a large short circuit current.
--------

Yes -you are shorting a part of the winding but the switching is a bit more
complex than that so that short circuit currents are limited to reasonable
values. It is a multistep operation with reactor switching. On-load tap
changers are expensive and are generally limited to applications where this
is absolutely needed (I have seen one where the tap changer was nearly as
large as the transformer).
--------------

Certainly modern ones likely use thyristors and zero crossing detectors.
-------------

Possibly but probably not- I am out of date on this but I would expect that
the old way of good switches plus reactors might still be the better way. It
saves a lot of control wiring plus a lot of money to operate thyristors at
300KV and 500A or more and I doubt whether they would be cost effective or
technically advantageous otherwise. --------------------------

When I was a kid living in a rather rural area, there would be a pair of
these on poles every few miles, connected open delta. (all transformer
primaries were connected phase-phase then).

"on load tap changers"? Not likely. These were applied to transformers only
where it was worth the effort.
Definitely transformers in rural areas- typical pole pigs- would have to be
de-energized as the tap changer is a manually operated switch inside the
tank. Some larger transformers did have off-load but live changers operated
from ground level. What you saw could have been somethng else altogether.
Delta primaries as you indicate were around when you were a kid, would, in
most areas mean that you are now a pensioner. I remember cases of conversion
from delta to star for distribution primaries in small towns being done
about 60 years ago and use of delta for transmission died much before that.
--

Don Kelly dhky@shawcross.ca
remove the X to answer

 

[Don Kelly]

----------------------------
"Michael Moroney" <moroney@world.std.spaamtrap.com> wrote in message
news:g0a1o5$bcq$1@pcls6.std.com...

"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> writes:


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.

Are the load tap generators configured make-before-break?
Break-before-make would mean a (very short) power outage every activation
but make-before-break would mean a momentarily short-circuited winding and
the break would involve interrupting a large short circuit current.
--------

Yes -you are shorting a part of the winding but the switching is a bit more
complex than that so that short circuit currents are limited to reasonable
values. It is a multistep operation with reactor switching. On-load tap
changers are expensive and are generally limited to applications where this
is absolutely needed (I have seen one where the tap changer was nearly as
large as the transformer).
--------------

Certainly modern ones likely use thyristors and zero crossing detectors.
-------------

Possibly but probably not- I am out of date on this but I would expect that
the old way of good switches plus reactors might still be the better way. It
saves a lot of control wiring plus a lot of money to operate thyristors at
300KV and 500A or more and I doubt whether they would be cost effective or
technically advantageous otherwise. --------------------------

When I was a kid living in a rather rural area, there would be a pair of
these on poles every few miles, connected open delta. (all transformer
primaries were connected phase-phase then).

"on load tap changers"? Not likely. These were applied to transformers only
where it was worth the effort.
Definitely transformers in rural areas- typical pole pigs- would have to be
de-energized as the tap changer is a manually operated switch inside the
tank. Some larger transformers did have off-load but live changers operated
from ground level. What you saw could have been somethng else altogether.
Delta primaries as you indicate were around when you were a kid, would, in
most areas mean that you are now a pensioner. I remember cases of conversion
from delta to star for distribution primaries in small towns being done
about 60 years ago and use of delta for transmission died much before that.
--

Don Kelly dhky@shawcross.ca
remove the X to answer

 

[Don Kelly]

----------------------------
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:4828b193$0$7075$4c368faf@roadrunner.com...

phil-news-nospam@ipal.net> wrote in message
news:g0a7ts1t0c@news5.newsguy.com...
In alt.engineering.electrical Michael Moroney
moroney@world.std.spaamtrap.com> wrote:

| Are the load tap generators configured make-before-break?
| Break-before-make would mean a (very short) power outage every
activation
| but make-before-break would mean a momentarily short-circuited winding
and
| the break would involve interrupting a large short circuit current.

I wonder how much regulation could be managed through the use of variable
leakage inductance in the transformer windings.


I suppose you could, but increasing leakage inductance means you're
increasing losses aren't you? Just a percent or two on a unit rated for
250 MVA can be too much to tolerate.

daestrom
-------------

I don't see changing leakage inductance having much effect on losses ( a
great effect on voltage regulation -likely all to the bad) but the problem
is one of changing leakage inductance.
Does this mean changing a gap in the core? Does it mean moving one winding
with respect to another? In any case it does mean some fiddling with the
core or winding.
This has been done for series lighting circuits where the load current was
kept constant by using a transformer which balanced the forces between coils
against a fixed weight. If the current changed the secondary coil moved so
that there was more or less leakage. The units that I have seen were rather
cumbersome.

--

Don Kelly dhky@shawcross.ca
remove the X to answer

>

 

[Don Kelly]

----------------------------
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:4828b193$0$7075$4c368faf@roadrunner.com...

phil-news-nospam@ipal.net> wrote in message
news:g0a7ts1t0c@news5.newsguy.com...
In alt.engineering.electrical Michael Moroney
moroney@world.std.spaamtrap.com> wrote:

| Are the load tap generators configured make-before-break?
| Break-before-make would mean a (very short) power outage every
activation
| but make-before-break would mean a momentarily short-circuited winding
and
| the break would involve interrupting a large short circuit current.

I wonder how much regulation could be managed through the use of variable
leakage inductance in the transformer windings.


I suppose you could, but increasing leakage inductance means you're
increasing losses aren't you? Just a percent or two on a unit rated for
250 MVA can be too much to tolerate.

daestrom
-------------

I don't see changing leakage inductance having much effect on losses ( a
great effect on voltage regulation -likely all to the bad) but the problem
is one of changing leakage inductance.
Does this mean changing a gap in the core? Does it mean moving one winding
with respect to another? In any case it does mean some fiddling with the
core or winding.
This has been done for series lighting circuits where the load current was
kept constant by using a transformer which balanced the forces between coils
against a fixed weight. If the current changed the secondary coil moved so
that there was more or less leakage. The units that I have seen were rather
cumbersome.

--

Don Kelly dhky@shawcross.ca
remove the X to answer

>

 

[Arfa Daily]

"James Sweet" <jamessweet1@trashmail.net> wrote in message
news:cwqVj.114$ll1.71@trndny06...

Brian wrote:
Meat Plow wrote:
On Sat, 10 May 2008 07:42:57 -0500, Brian wrote:

You might try to charge the batteries with a conventional charger or
variable power supply for an hour or so at a low current then replace
them
in the unit.

Thanks, I'll give it a try! I have a one-amp 12V trickle charger that I
use for cars. Will let y'all know what happens, on Tuesday or so.

Otherwise, I see cheapee replacement batteries on eBay, ~$40 delivered
for the needed two batteries.

-Brian


Beware cheap Chinese knockoff batteries, they've been known to fail
quickly and/or leak.

I put a pair of 'cheap' batteries in my APC 700 when the originals failed.
They lasted all of a few months before it kept falling over again when it
performed its auto self test every couple of weeks. Kept doing it in the
middle of the night so we thought it was a smoke alarm going off. A new pair
of 'proper' priced ones restored it. Also, be very careful that you get
replacements with the right sized spades. Before fitting the cheapies, I had
already tried a pair of batteries with similar size and capacity, but small
tags. These were in good condition and still give good heavy duty service
now in another application. However, with the large connectors in the APC
700, pushed onto the small tags on the batteries, there was just not enough
contact area, and it fell over every time at powerup, when it does its load
test, and checks for battery terminal voltage drop.

Arfa

 

[Arfa Daily]

"w_tom" <w_tom1@usa.net> wrote in message
news:4fd8b3fe-2dcf-4093-8c85-97643ff9e694@u36g2000prf.googlegroups.com...
On May 11, 11:56 am, "William Sommerwerck"
<grizzledgee...@comcast.net> wrote:

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)

No reason to remove or disconnect those batteries. Simply connect a
VDC multimeter to battery terminals. If voltage rises when UPS is
connected to AC, then UPS charger is working. Same charger test
performed without removing anything also tests other UPS hardware.
Procedure tests both items simultaneously. Learn more, faster, by
also doing less labor. Use a meter.

But it's just been explained that one of the relays is in series with the AC
input line, and doesn't close unless there is at least some residual charge
on the batteries. Therefore, it would seem that there is every need to
disconnect and at least sub those batteries, before being able to carry out
any kind of charging test. I would further suggest that a simple charge
voltage test, may not give an accurate picture of what is actually happening
in the charging circuit. Even a charge current test, although a better
indication, may not be sufficient, unless you know what the charge limit
current should be, either for all or specific battery discharge conditions.
FWIW, I can also confirm that an APC 700 model will not even try to start up
without a partially charged battery fitted.

Arfa

 

[Tzortzakakis Dimitrios]

? "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> ?????? ??? ??????
news:4828b130$0$7047$4c368faf@roadrunner.com...

"Michael Moroney" <moroney@world.std.spaamtrap.com> wrote in message
news:g0a1o5$bcq$1@pcls6.std.com...
"daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> writes:


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.

Are the load tap generators configured make-before-break?
Break-before-make would mean a (very short) power outage every activation
but make-before-break would mean a momentarily short-circuited winding
and
the break would involve interrupting a large short circuit current.

Certainly modern ones likely use thyristors and zero crossing detectors.


I figured someone would 'bite'

Typical large power load-tap-changers have a primary winding and two
secondaries.
You mean a secondary and a tetriary? The transformer for the hotel load of a

300 MW unit is powered directly from the turbo alternator (21 kV) and has a
secondary of 6.6 kV and a tetriary of again 6.6 kV. This is done because it
has wye-wye-wye connection (IIRC). The hotel load of such a unit is 10%,
also 30 MW, including 7 brown coal mills. Typical size of a 6.6 kV motor is
1 MW.

One secondary produces about 100% of 'rated' secondary voltage. The second
secondary produces about 15% to 20% of the rated voltage, but has numerous
taps from end to end, about 2.5% 'steps'. (for a total of about eight
taps). The cental tap of the boost/buck winding is tied to one end of the
main secondary. The boost/buck can be used to step from 90% to 110% of the
'design' output. I suppose some can step over a wider range, but I haven't
run across them.

*TWO* rotary switches have each tap tied to one of the positions of each
rotory switch, and each 'wiper' is tied to single heavier contacts that
are opened in the operating sequence. The output side of these two
interrupting contacts are tied to each end of a large center-tapped
inductor.

So, normally both rotary switches are aligned to the same transformer tap,
both interrupting contacts are shut, and load current flows from the
boost/buck winding tap, splits and flows through both rotary switches,
both interrupting contacts, enters both ends of the inductor and out the
inductor center tap. Because the current flows into both ends of the
inductor and the mutual inductance of the two parts cancel, there is
little voltage drop in the inductor.

Begin step sequence:
1) Open one interrupting contactor. Now load current doubles through half
the inductor and is zero in the other half, so the voltage drop across the
inductor actually makes output voltage drop, even if trying to step 'up'.
2) Move associated rotary switch to next step of transformer bank.
3) Close interrupting contactor. Now, the two rotary switches are across
different taps. The inductor prevents a excessive current, otherwise you
have a direct short of the two winding taps. Some tap changers can stop
at this point and are called 'half-step' units. Obviously, the inductor
has to be rated for sustained operation across a step of the boost/buck
winding plus load current in order to survive sustained 'half step'
operation.
4) But for tap changers that can't operate 'half-step', the sequence
continues. And opens the other interrupting contactor. Now the other
half of the inductor has full load current.
5) Move second rotary switch to next step (now both switches are on the
new step)
6) Close the second interrupting contactor. You're back in the initial
configuration, but with both rotary switches on a new transformer tap.
Quite the same principle is done with diesel locomotives and is called

diesel-electric transmission, and also in pure electric locomotives (E-Lok
in german, for Elektrische Lokomotive). The diesel engine, 2-stroke and
usually 600 to 900 rpm at full throttle, is coupled to a generator. The
generator has small windings, connected in series for the last notch, higher
voltage and relatively smaller current, and in parallel for start, higher
amperage and smaller voltage. The traction motors are directly coupled on
the wheel shaft, and are air cooled. An E-Lok has a trasformer, with the
primary directly supplied by the cetenary, 15 kV 16 2/3 Hz in Germany, and
25 kV 50 Hz in Greece, The secondary uses the same principle. The typical
size of a traction motor is 1 MW, 4 (one each shaft) and maximum voltage 700
volts, and are series wound motors with special construction to operate at
16 2/3 Hz (or 50 Hz with today's technology). Typical power of a diesel
locomotive is 2850 HP, while an electric is 6000 HP. with 1500 HP at each
shaft, also ~1MW. There is a heavy duty 12,000 HP diesel engine in USA(with
6 shafts, also 2000 HP at each shaft). The high speed ICE train
(InterCityExpress) in germany is 13,000 HP, has a normal travelling speed of
200 km/h, 2 locomotives, 3-phase induction motors, electronic drive.

Older units do this whole thing with a fancy cam/gear arrangement circa
1940's. Just takes a single reversable motor to drive the unit and some
limit switches to be sure it can only stop at full 'steps' (or 'half
steps' for those capable of running 'half-step')

The one we have here operates with a motor.
Because the system intermittently inserts an additional voltage drop
through the inductor, the control circuits typically have time-delays that
prevent it trying to reverse direction or something while stepping.

As far as zero-crossing and thyristors, I suppose it's certainly possible,
but I haven't run across them for large substations. I have seen such a
setup in power-conditioners for computer complexes and such, but that's
only a few kVA (one unit I know of was rated for 25 kVA).

The mechanical-switch tap changer is well-matured and has the nice
advantage that when they 'fail', they 'fail' at the last 'step' and power
continues to flow (albeit perhaps the wrong voltage).

When I was a kid living in a rather rural area, there would be a pair of
these on poles every few miles, connected open delta. (all transformer
primaries were connected phase-phase then).

Those are smaller than the units I'm thinking of. I'm talking about
multiple MVA rated units.

I had no idea how it really works, but I got the general idea.

--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr
NB:I killfile googlegroups.

 

[Tzortzakakis Dimitrios]

Ď <phil-news-nospam@ipal.net> Ýăńářĺ óôď ěŢíőěá
news:g0a7lq0t0c@news5.newsguy.com...

In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void
wrote:

| 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.

And the latter make easy terrorism targets, too.

I cross my fingers that terrorists get no electrical engineering degree:0

| 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).

You don't use 400 V for anything heavy duty like an oven?

Yep. All ovens sold in EU are wired for 3 phase, 400 V with neutral (and

earth, goes without saying). Just if you connect it on 1 phase (as usually)
you use a bridge, and connect all L1-L2-L3 to the one and only hot. 230 V is
powerful enough for almost everything in a house, only large airconditioners
are 3 phase, and all industrial motors, even if they are 1HP (

--

--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr
NB:I killfile googlegroups.

 

[Ol' Duffer]

Don't post a bunch of links and expect anyone to follow them.
If you have something to say, just say it.

In article <22ada323-fe66-4793-980f-
42c18061305a@p39g2000prm.googlegroups.com>, jeffm_@email.com says...

Your use of Usenet
http://groups.google.com/groups/search?enc_author=PPty2hYAAACMqG273ADuJvt-JkA5nW4iK5_ckrHRAYuDYR832hY26Q&scoring=d
http://groups.google.com/groups/search?q=permanent-magnets-as-coil-cores&scoring=d&filter=0

needs improvement.
http://www.google.com/search?q=cache:qHhBKJ-sXKYJ:en.wikipedia.org/wiki/Cross-post+adequately.answered+corrected+with.commas+individually+Disclaimers+*-*-*-marked-as-Read-in-ALL-*-groups+Newsgroups.line
More here:
http://groups.google.com/group/sci.electronics.basics/browse_frm/thread/7b7c0624331012bb/3958f18673b5f374?q=EVERY-group-*-*-*-*-*-*-*-*-appear+*-proper-answer-*-*-*-given+much-easier-*-*-*-*-*-*-*+*-frowned-on+*-correcting+*-Followup-To-*+*-*-_perfect_-*-*-*-*+*-*-*-too-lazy-*-*-*-*-*-appropriate-*+*-polite-*-mention-*-*-*-*-*-*-*+Just-because-*-*-*-*-*-*-*-*-does-not-mean-*-*-*-*-*-*+mark-*-*-*-*-all-*-groups+*-*-*-*-two-groups-*-*-aren't-*-different
http://groups.google.com/group/sci.electronics.basics/browse_frm/thread/7b7c0624331012bb/9bba213e1c4c044f?q=EVERY-group-*-*-*-*-*-*-*-*-appear+*-proper-answer-*-*-*-given+much-easier-*-*-*-*-*-*-*+*-frowned-on+*-correcting+*-Followup-To-*+*-*-_perfect_-*-*-*-*+*-*-*-too-lazy-*-*-*-*-*-appropriate-*+*-polite-*-mention-*-*-*-*-*-*-*+Just-because-*-*-*-*-*-*-*-*-does-not-mean-*-*-*-*-*-*+mark-*-*-*-*-all-*-groups+*-*-*-*-two-groups-*-*-aren't-*-different

 

[Michael Moroney]

"Don Kelly" <dhky@shaw.ca> writes:

"Michael Moroney" <moroney@world.std.spaamtrap.com> wrote in message
news:g0a1o5$bcq$1@pcls6.std.com...

Are the load tap generators configured make-before-break?
Break-before-make would mean a (very short) power outage every activation
but make-before-break would mean a momentarily short-circuited winding and
the break would involve interrupting a large short circuit current.
--------
Yes -you are shorting a part of the winding but the switching is a bit more
complex than that so that short circuit currents are limited to reasonable
values. It is a multistep operation with reactor switching. ...

Thanks for your (and esp. daestrom's) explanation on how they work.

When I was a kid living in a rather rural area, there would be a pair of
these on poles every few miles, connected open delta. (all transformer
primaries were connected phase-phase then).

"on load tap changers"? Not likely. These were applied to transformers only
where it was worth the effort.
Definitely transformers in rural areas- typical pole pigs- would have to be
de-energized as the tap changer is a manually operated switch inside the
tank. Some larger transformers did have off-load but live changers operated
from ground level. What you saw could have been somethng else altogether.

I'm not completely sure what these are other than being told that they
were voltage regulators (tapped autotransformers) long ago. These are
large cans with 3 bushings on top, taller and slimmer than most pole pigs,
and they usually have a control box on the pole around eye level. I see
the same style cans in substations between the stepdown transformer and
the distribution system except they sit on the ground and come in sets of
three.

Delta primaries as you indicate were around when you were a kid, would, in
most areas mean that you are now a pensioner. I remember cases of conversion
from delta to star for distribution primaries in small towns being done
about 60 years ago and use of delta for transmission died much before that.

While I'm hardly a kid, I'm no pensioner yet. In fact my father's place
still has delta-connected distribution primaries in the area, at 7200
volts (I have an old fuse/switch holder from there labelled 7200V ??A).

Where I mentioned they had pairs of these "voltage regulators" (or
whatever they were) every several miles was a long run along a state
highway. At some point they upgraded it to a wye configuration, probably
at a higher voltage. However, several side branches haven't been upgraded
yet. On the side branch feeding my father's place there is a bank of 3
transformers connected wye-delta immediately followed by a pair of these
"voltage regulator" cans connected open delta. From that point on the
distribution system is visibly old.

 

[Michael Kennedy]

"James Sweet" <jamessweet1@trashmail.net> wrote in message
news:fa5Wj.181$Pr1.149@trndny03...

Brian wrote:
James Sweet wrote:


They can hold up to a tremendous amount of abuse, but deep discharging
will kill them just about every time.

And the result is ...

They wouldn't even start to take a charge. My trickle charge reported
both were fully charged, even though they were totally dead. Even a
couple of hours on each wouldn't make them budge.

So, time for some new batteries. The originals were made in China. Will
hopefully remember to post whether the new batteries fixed the unit.

-Brian

P.S. There are four small-matchbox size black boxes on the unit's PCB. I
think they are relays. My guess would be that the batteries must have
some juice to keep one of these relays closed -- and that relay admits
line voltage to the entire device. Would explain the total non-response
from the UPS when plugged in with dead batteries.


You can hook up just about any lead-acid battery of the correct voltage
for testing, should be fine to jumper it to your car battery to see if it
powers up, mind the polarity though.

I used two car batteris to power my UPS during a hurricane here a few years
ago.

Note: Some SmartUPS units require 24 volts.. i.e. 2 12v batteries in series
to run.

Mike

 

In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void> wrote:
|
| ? <phil-news-nospam@ipal.net> ?????? ??? ??????
| news:g0a7lq0t0c@news5.newsguy.com...
|> In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void>
|> wrote:
|>
|> | 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.
|>
|> And the latter make easy terrorism targets, too.
|>
| I cross my fingers that terrorists get no electrical engineering degree:0

I suspect quite many already have them. Many have degrees in a lot of other
things like chemistry and physics. Some even have doctoral level degrees.


|> | 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).
|>
|> You don't use 400 V for anything heavy duty like an oven?
|>
| Yep. All ovens sold in EU are wired for 3 phase, 400 V with neutral (and
| earth, goes without saying). Just if you connect it on 1 phase (as usually)
| you use a bridge, and connect all L1-L2-L3 to the one and only hot. 230 V is
| powerful enough for almost everything in a house, only large airconditioners
| are 3 phase, and all industrial motors, even if they are 1HP (

That means each element individually runs on 230 V and they just divided them
up in three approximately equal sections, or use triple elements for each type
of use.

How many things that have just ONE (large) element would have it available in
both 230 V and 400 V versions?

--
|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 Tzortzakakis Dimitrios <noone@nospam.void> wrote:
|
| ? <phil-news-nospam@ipal.net> ?????? ??? ??????
| news:g0a7lq0t0c@news5.newsguy.com...
|> In alt.engineering.electrical Tzortzakakis Dimitrios <noone@nospam.void>
|> wrote:
|>
|> | 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.
|>
|> And the latter make easy terrorism targets, too.
|>
| I cross my fingers that terrorists get no electrical engineering degree:0

I suspect quite many already have them. Many have degrees in a lot of other
things like chemistry and physics. Some even have doctoral level degrees.


|> | 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).
|>
|> You don't use 400 V for anything heavy duty like an oven?
|>
| Yep. All ovens sold in EU are wired for 3 phase, 400 V with neutral (and
| earth, goes without saying). Just if you connect it on 1 phase (as usually)
| you use a bridge, and connect all L1-L2-L3 to the one and only hot. 230 V is
| powerful enough for almost everything in a house, only large airconditioners
| are 3 phase, and all industrial motors, even if they are 1HP (

That means each element individually runs on 230 V and they just divided them
up in three approximately equal sections, or use triple elements for each type
of use.

How many things that have just ONE (large) element would have it available in
both 230 V and 400 V versions?

--
|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) |