(Michael Moroney) writes:

Rather, it's the ready market of consumer appliances that would take
advantage of them. That would require many houses to have them.

Yes the inability to go to the nearest WallyWorld and buy a 240V 4kW
cooker/microwave/whatever is a big problem. European appliance could be
got, but I'd worry about anything with a motor (50 Hz), clock (do their
electronic clocks operate off the line frequency like some in the US?),
microwaves (don't they use frequency-dependent constant voltage
transformers?).

I don't know if microwave ovens still use ferroresonant transformer
supplies. I'd heard that they'd moved to switchers but have not
worked on any with same. It would make sense: good transformer iron
& copper ain't cheap... and a switcher would also save shipping weight.

And yes, the clock would run fast.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

I don't know if microwave ovens still use ferroresonant transformer
supplies. I'd heard that they'd moved to switchers but have not
worked on any with same. It would make sense: good transformer iron
& copper ain't cheap... and a switcher would also save shipping weight.

And yes, the clock would run fast.



Some use switchers, they'll be much lighter and say "Inverter"
prominently on the front of the unit.

I've never seen one with a ferro-resonant transformer. They use a
standard laminated core power transformer with a pair of magnetic shunts
to regulate the current. Every one that I've ever worked on has exactly
the same circuit, 2KV RMS transformer feeds a charge pump doubler
consisting of a diode and capacitor, feeding 4KV pulsed DC to the
magnetron. Heater voltage is obtained from a tap at one end of the
secondary, usually physically it's several turns of much heavier wire
next to the HV winding wired in series with it.

James Sweet writes:



I've never seen one with a ferro-resonant transformer. They use a
standard laminated core power transformer with a pair of magnetic shunts
to regulate the current.

[Johnny Carson voice] "I did not know that...."

All I've ever had to a u-w power supply was to replace the rectifier
stack; or junk the oven because it was clearly smoked...

Someone one mentioned they were F-R, and a casual look seemed to confirm
that, so I never questioned it. A F-R is also current limited; short the
output and it delivers rated current, period..



--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

David Lesher writes:

James Sweet writes:



I've never seen one with a ferro-resonant transformer. They use a
standard laminated core power transformer with a pair of magnetic shunts
to regulate the current.

[Johnny Carson voice] "I did not know that...."

All I've ever had to a u-w power supply was to replace the rectifier
stack; or junk the oven because it was clearly smoked...

Someone one mentioned they were F-R, and a casual look seemed to confirm
that, so I never questioned it. A F-R is also current limited; short the
output and it delivers rated current, period..

Never seen an FR uwave. Why would they use that when the basic
circuit is adequate and reliable (more or less!)?

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
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Sam Goldwasser wrote:

Never seen an FR uwave. Why would they use that when the basic
circuit is adequate and reliable (more or less!)?

Mostly less! :-) My Panasonic inverter unit just released the magic
smoke. First the magenetron died, and then after I replaced that, an
IGBT in the switcher shorted and did a fair bit of collateral damage.

I finally did find a service manual...in spanish (which I read
poorly,) but it did at least tell me what all the small resistors and
diodes were supposed to be (before they melted.)

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/

On Thu, 29 May 2008 22:19:09 +0000 (UTC), David Lesher
wrote:

All I've ever had to a u-w power supply was to replace the rectifier
stack; or junk the oven because it was clearly smoked...

Someone one mentioned they were F-R, and a casual look seemed to confirm
that, so I never questioned it. A F-R is also current limited; short the
output and it delivers rated current, period..

The transformer goes by several names, depending on where you are. Variable
reluctance, leakage flux, stray flux, etc. It is exactly the same
construction and operating principle as a neon transformer, some kinds of HID
light ballasts and some series streetlight constant current transformers.

The core is an almost standard "E" core (or "H" core if you prefer) with one
exception. The center leg has an air gap. The windings are on the end legs
of the "E" instead of the center leg.

There are two magnetic paths around the core for the field set up by the
primary to travel. Around the periphery and across the secondary and around
the center leg and across the air gap. Field that travels along the center
leg does not cross the secondary and induces no voltage.

With no load applied, the bulk of the field travels the peripheral, very much
lower reluctance solid iron path, inducing full secondary voltage proportional
to the turns ratio. As current flows in the secondary, counter-MMF raises the
reluctance of the peripheral path so that some of the flux travels through the
center leg. With less flux traveling around the periphery and cutting across
the secondary, the secondary voltage drops as the current remains about the
same. At the limit, if the secondary is shorted, the peripheral path has so
much reluctance that most of the flux travels the center leg and across the
air gap. The same current as before flows through the secondary but at zero
volts.

When the dimensions of the core and gap are set up correctly, the transformer
behaves as an almost perfect constant current device. That is, the secondary
voltage varies as necessary to keep the same current flowing through a varying
load. Just what the doctor ordered to keep the magnetron happy.

The secondary current can be increased by opening up the air gap. This raises
the reluctance of that path and forces more field through the secondary leg.
Closing the gap has the opposite effect.

The center leg is often called the magnetic shunt and frequently it is a
separate piece of laminated iron stuck between the coils and TIG welded in
place. It is a common trick for Tesla Coilers to open up a neon transformer
and either knock out the shunt entirely or grind it down to open the air gap.
This modification causes the transformer to output much more current than it
is designed for - for a little while, at least :-) The same thing works with
microwave oven transformers (MOT).

This design in a microwave oven is a vital part of keeping the magnetron anode
current within spec. The magnetron is electrically a diode. A diode that
isn't emission-limited would draw destructive current if not externally
limited. With this design, the filament can be heated good and hot for long
life and not have the tube run away. The design also is vital for protecting
the magnetron from potentially damaging conditions such as operating the oven
empty, arcing, etc.

It's popular to use several MOTs to build an arc welder. This works quite
well specifically because these transformers are constant-current devices -
exactly the characteristic stick welding needs. If they were conventional
transformers, the first time the rod touched the work and shorted the
secondary, fault current would flow and the breaker would trip or blue smoke
would leak out.

Along similar lines, one can cut off the high voltage secondary and replace it
with a suitable number of turns of heavy wire, connect a bridge rectifier and
have a nice constant current battery charger. Select the turns carefully and
it'll do the bulk/absorption stages of the smart 3 stage charging algorithm.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com -- best little blog on the net!
Tellico Plains, Occupied TN
In theory, there is no difference between theory and practice. In practice, there is.

On Fri, 30 May 2008 01:50:29 GMT, (Fiat Sparks) wrote:

Sam Goldwasser wrote:

Never seen an FR uwave. Why would they use that when the basic
circuit is adequate and reliable (more or less!)?

Mostly less! :-) My Panasonic inverter unit just released the magic
smoke. First the magenetron died, and then after I replaced that, an
IGBT in the switcher shorted and did a fair bit of collateral damage.

I finally did find a service manual...in spanish (which I read
poorly,) but it did at least tell me what all the small resistors and
diodes were supposed to be (before they melted.)

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/


Don't try to operate that oven from a cheap generator with a less than perfect
sine output. That's another excuse for the blue smoke to leak out. BTDT.

In my case I wasn't about to spend that kind of money to repair an oven that
barely cost that much, especially since I used it in my restaurant always on
high. Therefore I yanked out all those fancy electronics and installed the
transformer/diode/cap assembly from another old oven. I drilled a hole
through that nice touch pad and installed an Intermatic spring-wound timer
from Home Depot.

Viola, good as new and bullet-proof against nasty power.

John

--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com -- best little blog on the net!
Tellico Plains, Occupied TN
The secret to creativity is knowing how to hide your sources -Albert Einstein

(Fiat Sparks) writes:

Sam Goldwasser wrote:

Never seen an FR uwave. Why would they use that when the basic
circuit is adequate and reliable (more or less!)?

Mostly less! :-) My Panasonic inverter unit just released the magic

Sorry, I was referring mostly to the normal transformer/capacitor/diode
circuit.

smoke. First the magenetron died, and then after I replaced that, an
IGBT in the switcher shorted and did a fair bit of collateral damage.

I finally did find a service manual...in spanish (which I read
poorly,) but it did at least tell me what all the small resistors and
diodes were supposed to be (before they melted.)

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/



--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

David Lesher writes:

(Michael Moroney) writes:


I also asked about tap changers/regulators. Is this what these are, and
if so, are they likely to be manual or automatic?

http://tinyurl.com/534ffq (Google Maps street view of a set of 3 on a pole
in upstate NY. You may have to click on street view and rotate to see them)


Yes. Note the primaries are broken by insulators, and there is no
secondary [240/120] service on the pole. [The lowest run is TV coax, then
neutral above it.]

I've never heard of such as manual regulators so I assume they are
automatic.

Earlier in this thread it was mentioned the automatic ones are expensive
and only used for big substations, not for long runs of distribution
systems like that one. Before I read that I assumed they must be
automatic.

It's somewhat unusual to see all three on one pole; it must be a BIG
one. Generally I see them staggered on 3 adjacent poles; or two poles
hold a platform between them.

At that location there used to be 2 adjacent poles with 3 transformers
on a platform between them, when the downstream was an older delta-
connected system. I bet they just reused one of the heavy duty poles.
I wonder why they simply didn't reuse the platform setup.

I wonder what each of those puppies weigh, and how many MVA they can
handle.

(Michael Moroney) writes:

Yes the inability to go to the nearest WallyWorld and buy a 240V 4kW
cooker/microwave/whatever is a big problem. European appliance could be
got, but I'd worry about anything with a motor (50 Hz), clock (do their
electronic clocks operate off the line frequency like some in the US?),
microwaves (don't they use frequency-dependent constant voltage
transformers?).

A motor designed for 50 Hz would run fast on 60 Hz, which might
overload something like a fan motor. A clock would run fast. On the
other hand, more iron is needed for 50 Hz motors (at a given voltage
and number of turns), so the motor is actually overbuilt for 60 Hz
operation. Same goes for ordinary transformers.

I've taken a number of microwave ovens apart over the years, and none of
them used constant-voltage transformers. They do have a magnetic shunt
to give them somewhat of a constant *current* characteristic, and that
might reduce the magnetron current some when operated from 60 Hz.
The magnetron itself operates from half-wave rectified DC, so it
shouldn't care.

Some Panasonic microwave ovens use an inverter to generate the HV supply
for the tube. Feeding it 60 Hz instead of 50 Hz should not be a
problem; it will just reduce the ripple at the output of the initial
rectifier.

Dave

David Lesher writes:

Someone one mentioned they were F-R, and a casual look seemed to confirm
that, so I never questioned it. A F-R is also current limited; short the
output and it delivers rated current, period..

They look similar. Both transformers have magnetic shunts, and there's
a big capacitor near the transformer. But the circuits are different.

The FR transformer puts the capacitor across the secondary winding, or
two secondary windings in series, and the windings plus capacitor
resonate at the designed line frequency. This causes the voltage to
rise above what you'd expect from the turns ratio alone, but the voltage
is limited by the portion of the core that the secondary is wound on
going into saturation. Sometimes the secondary voltage waveform looks
pretty square because of this peak clipping, but sometimes there's a
third winding that (somehow) reduces the second harmonic and gives
something closer to a sine wave.

There's a magnetic shunt between the primary and secondary windings so
that the primary current doesn't go through the roof when the iron in
the secondary saturates. It limits the shorted output current to about
*twice* the rated current, not equal to the rated current.

Still, the FR transformer runs hot with no load, dissipating about 20%
of its full output rating as heat.

In comparison, the capacitor in the microwave is wired as part of a
voltage doubler; it doesn't resonate with the transformer secondary.
The transformer iron is not designed to saturate (though, as an
intermittent-duty transformer that is fan-cooled in use, it is
apparently designed to operate close to saturation to minimize the
amount of iron).

Dave

(Fiat Sparks) writes:

Mostly less! :-) My Panasonic inverter unit just released the magic
smoke. First the magenetron died, and then after I replaced that, an
IGBT in the switcher shorted and did a fair bit of collateral damage.

Ouch. We have one that's only a few months old; I hope it does better
than that. I love it because all of the power settings from "3" to "10"
actually vary the magnetron RF output while keeping it on continuously.
At "3", I can cook a single egg in the oven without it exploding.

Conventional microwaves set to "3" run the magnetron about 4.5 seconds
at full power followed by about 10.5 seconds off, and 4.5 seconds of
full power into a single egg generates enough steam for an explosion.

(On the Panasonic, settings of "1" and "2" actually run the magnetron at
30% power, using 1/3 and 2/3 on time).

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/

For that much, I'd be tempted to scrap it and buy a new oven.

Dave

Neon John wrote:
see originsl post

It's popular to use several MOTs to build an arc welder. This works quite
well specifically because these transformers are constant-current devices -
exactly the characteristic stick welding needs. If they were conventional
transformers, the first time the rod touched the work and shorted the
secondary, fault current would flow and the breaker would trip or blue smoke
would leak out.

Along similar lines, one can cut off the high voltage secondary and replace it
with a suitable number of turns of heavy wire, connect a bridge rectifier and
have a nice constant current battery charger. Select the turns carefully and
it'll do the bulk/absorption stages of the smart 3 stage charging algorithm.

Another use for defunct MOT's, even those with a bad HV winding, is
using two as a line isolation transformer. Just remove the HV winding,
and connect the two magnetron heater windings together. The normal line
winding on the second transformer then supplies your workbench with
power isolated from the line. (You might need to modify the "shunt" core.)

With a Variac on the input, this is a handy for working on line operated
devices that might have a line-to-chassis defect.

--
Virg Wall

(Dave Martindale) wrote in news:g1pa8d$ljv$2
@swain.cs.ubc.ca:

Conventional microwaves set to "3" run the magnetron about 4.5 seconds
at full power followed by about 10.5 seconds off, and 4.5 seconds of
full power into a single egg generates enough steam for an explosion.



Saw something in a catalogue: a plastic 'Egg' shaped chamber that holds 4
eggs and some water. I am guessing that it is a 'plastic pressure cooker'.
Anyway, they claim you can hard boil eggs in it in a microwave oven.



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

(Dave Martindale) wrote:

Ouch. We have one that's only a few months old; I hope it does better
than that. I love it because all of the power settings from "3" to "10"
actually vary the magnetron RF output while keeping it on continuously.
At "3", I can cook a single egg in the oven without it exploding.

Mine lasted about eight years with daily use for a family of 5. So,
hopefully you've got a ways to go. I agree, it does cook nicely, which
is why I even bothered to repair it.

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/

For that much, I'd be tempted to scrap it and buy a new oven.

You know, that's what the wife said! :-)

Had I known it was going to go out again after the magenetron died, I
probably would have. But, my pride was at stake!

(Michael Moroney) writes:


I've never heard of such as manual regulators so I assume they are
automatic.

Earlier in this thread it was mentioned the automatic ones are expensive
and only used for big substations, not for long runs of distribution
systems like that one. Before I read that I assumed they must be
automatic.

I know mine [which look to be very similar to the picture..] are
automatic -- after my PSC complaint, the PEPCO phone droid read off the
trouble report where the lineman went out, found higher-than-wanted
voltage on my phase and set it to manual until the correct person could
fix the regulator.

Alas, the first repair didn't work, as a week later, I was awoken
again....

Later conversations with lineman in the area confirmed both that detail;
and the fact their standard pole-pigs do NOT have a choice of taps.
[They replaced the pig serving me with a larger one a few years back.]


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

VWWall writes:

Neon John wrote:
see originsl post

It's popular to use several MOTs to build an arc welder. This works quite
well specifically because these transformers are constant-current devices -
exactly the characteristic stick welding needs. If they were conventional
transformers, the first time the rod touched the work and shorted the
secondary, fault current would flow and the breaker would trip or blue smoke
would leak out.
Along similar lines, one can cut off the high voltage secondary and
replace it
with a suitable number of turns of heavy wire, connect a bridge rectifier and
have a nice constant current battery charger. Select the turns carefully and
it'll do the bulk/absorption stages of the smart 3 stage charging
algorithm.

Another use for defunct MOT's, even those with a bad HV winding, is
using two as a line isolation transformer. Just remove the HV
winding, and connect the two magnetron heater windings together. The
normal line winding on the second transformer then supplies your
workbench with power isolated from the line. (You might need to
modify the "shunt" core.)

With a Variac on the input, this is a handy for working on line
operated devices that might have a line-to-chassis defect.

Do you actually use a setup like that? I'd think that for any sort
of current, the filament windings would be melting down even though
they are made of fat wire. For example, at 300 VA of output, you're
looking at ~100 A in the filament winding.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

With a Variac on the input, this is a handy for working on line
operated devices that might have a line-to-chassis defect.

Do you actually use a setup like that? I'd think that for any sort
of current, the filament windings would be melting down even though
they are made of fat wire. For example, at 300 VA of output, you're
looking at ~100 A in the filament winding.




Connecting the HV windings together would probably work a lot better.
Would want to knock out the magnetic shunts too, that can be tricky but
I've done it on several without damaging the windings.

James Sweet wrote in news:HT%%j.670$BV.298
@trndny05:




With a Variac on the input, this is a handy for working on line
operated devices that might have a line-to-chassis defect.

Do you actually use a setup like that? I'd think that for any sort
of current, the filament windings would be melting down even though
they are made of fat wire. For example, at 300 VA of output, you're
looking at ~100 A in the filament winding.




Connecting the HV windings together would probably work a lot better.
Would want to knock out the magnetic shunts too, that can be tricky but
I've done it on several without damaging the windings.

I wanted some heavy copper wire to wind a coil with so I tore xxxx started
to tear up an old microwave transformer.
Found out that pretty copper wire was aluminum with a copper colored layer
on top of it.




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

Ï "danny burstein" Ýãñáøå óôï ìÞíõìá
...
In writes:

In alt.engineering.electrical Tzortzakakis Dimitrios
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.

And so does that 20 gallons of gasoline parked
in front of your house. And that 500 gallons
of diesel fuel in your basment. And that 20,000
or so gallons in the nearby gas station.

Good that terrorists are brain-washed lunatics, and haven't access to
incendiary rounds:-)
Yawn.




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

--
__________________________________________________ ___
Knowledge may be power, but communications is the key

[to foil spammers, my address has been double rot-13 encoded]

Ï Ýãñáøå óôï ìÞíõìá
...
In alt.engineering.electrical Tzortzakakis Dimitrios
wrote:

| ? ?????? ??? ??????
| ...
| In alt.engineering.electrical Tzortzakakis Dimitrios

| wrote:
|
| | Professional washing machines. One of my very first days 'in the
field'
| was
| | to connect some of them. They have a large heating element, you can
| connect
| | it single phase, or 3 phase, it just heats up faster (of course) when
| you
| | connect it 3 phase. (they have a single phase motor, so it works also
in
| | pure 230 V).
|
| If it has 3 elements rated for 230 volts, with 3 separate connections
that
| would be to three separate phase for a three phase feed, and all
connected
| to the one phase for a single phase feed, then it should heat up at the
| same
| speed, while drawing three times the current (not accounting for the
| motor).
|
| I don't know why it should heat up faster in three phase, or why you
would
| say "of course" about it. I would think it would heat up faster if you
| took
| it over to London and hooked it up to a 240 volt supply.
|
| Maybe you connected with single phase just one element? The rest two
| remained unconnected? (3 230 volts elements, connected wye). I'm sure it
| heated up faster, in 3 phase connection.

You were the one who said "it just heats up faster (of course) when you
connect it 3 phase."

I would disagree.

But the fact that you said "(of course)" seems you presume that to be the
general case. Now your most recent comment at least acknowledges that if
not all elements are connected, it won't heat up as fast.

In the simple case, each of 3 elements is individually wired, so you have
a total of 6 leads. When connecting to three phase, one lead of each is
connected to neutral, and each of the other leads is connected to separate
phases. When connecting to single phase, they are all wired in parallel.
Both cases always involve one of the leads from each element connected to
neutral, so those 3 leads can be pre-connected together. So you could
have
just 4 leads. The common neutral lead needs to be rated for all the
current
together for it to be rated properly for single phase.

It should apply the same voltage (230V) to each element, and they should
each
draw the same current. How would you believe this would be slower to
heat?

If the 3 elements were wired _internally_ in star without a neutral lead,
it would still work fine on three phase as long as all elements were equal
impedance. But on single phase, you could only activate 2 of the
elements,
and that would be 2 in series fed with 230 volts. You'd only get 1/6 the
power that way.

Are you assuming the elements would be wired that way? That would clearly
NOT be intended for single phase connection.

The 3 elements could be wired _internally_ in delta. In this case, these
would have to be 400V elements. Connecting 2 leads to 230 volts would
still
give you only 1/6 the power (but more evenly distributed in this case).

So what is the situation that makes _you_ believe that 3 elements
connected
to single phase _will_ draw less power to heat the water than when
connected
to three phase?

I have no idea, we didn't even open up the washing machines as they were
under guarantee. I know that the landlady's electrician connected the wms
single phase, and I connected (in the distr.box) all 3 phases. I suppose it
has 3 elements connected wye, and single phase is 1 element, plus motor and
automation.



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

? "James Sweet" ?????? ??? ??????
news:HKnVj.128$6D1.49@trndny02...



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


Mine dim slightly for an instant when my 3 ton heat pump kicks in, it's
only noticeable with the few incandescent lights left in the house though.
The LRA on that thing is something like 90A. I think most of the drop must
be in the 50' or so of 2/0 AL wire between the meter base and the
transformer though as they don't seem to dim at all from any of the
neighbors.
That's because you have no bloody wind-turbines on your grid. We have here,
and I had to include them in my thesis, and these things seriously harm the
voltage quality in interconnected grids. In stand-alone residence
installations, they work ok, probably with photovoltaics, but here they are
a disaster, in whole Crete all the lights flicker every evening when the
bloody wing stalls them and they convert momentarily from generating to
motors. I prefer old-fashioned fossil-fuel fired power plants, after all
smoking chimneys is a token of peace:-)



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

Tzortzakakis Dimitrios wrote:

That's because you have no bloody wind-turbines on your grid. We have here,
and I had to include them in my thesis, and these things seriously harm the
voltage quality in interconnected grids. In stand-alone residence
installations, they work ok, probably with photovoltaics, but here they are
a disaster, in whole Crete all the lights flicker every evening when the
bloody wing stalls them and they convert momentarily from generating to
motors. I prefer old-fashioned fossil-fuel fired power plants, after all
smoking chimneys is a token of peace:-)


You need to move your politicians closer to the turbines, to maintain
a higher efficiency. This detail os often overlooked in this type of
installation. ;-)


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wrote in message
...
In alt.engineering.electrical Daniel Who Wants to Know
wrote:

| Yes like my Amana commercial RadarRange which is 4KW in 2.2KW out and
has 3
| HV magnetrons along with 3 each of the other necessary items (cap,
diode,
| etc.). It even has a current transformer that tells the control board
via
| current draw when the magnetrons are warmed up so that the timer doesn't
| start counting down until it is actually cooking. It has a standard
NEMA
| 6-20 plug on it now and will pop a bag of popcorn in roughly 75 seconds
| without scorching it. I can tell you it sure beats the hell out of
regular
| microwave ovens for most things. The only thing I still use the regular
one
| for are items that involve liquids as the Amana tends to make them
either
| boil over or boils out all of the water before the food is cooked.

Will it operate on single phase power, like I have in my home?


Considering a NEMA 6-20 plug only has the 2 hot prongs plus ground and the
cord is a 14-3 AWG with one conductor being ground, yes it is single phase.
:-)

"msg" wrote in message
ernet...
Daniel Who Wants to Know wrote:

snip

Yes like my Amana commercial RadarRange which is 4KW in 2.2KW out and has
3 HV magnetrons along with 3 each of the other necessary items (cap,
diode, etc.).

Does this oven somehow injection-lock the magnetrons? Can you describe
the (RF) plumbing?

Michael

Each mag has its own waveguide with a rotating antenna at the end that
extends into the oven cavity. 2 of the waveguides are at the top of the
cavity firing down and the third is at the bottom firing up. The HV
transformer primaries are wired so that the top 2 mags fire on the positive
alternation of the AC sine wave and the bottom mag fires on the negative
alternation. The top 2 antennas are driven by a single timer motor with
large plastic gears (complete with timing marks) so that they both are
pointing the same direction at all times as they rotate. The HV
transformers have tapped primaries so that the oven can operate on either
208 or 230 volts with no change in output power. Also there is a small
208-230 volt boost autotransformer that boosts the voltage for the cavity
lamp, cooling blower, and antenna motors when the oven is plugged in to 208.
When the microwave is first plugged in it sits for about 30 seconds to (I
assume) to sense the supplied voltage and frequency so that it uses the
correct taps on the 4 transformers. Oh yeah when the oven is set for less
than 100% power the HV transformers are cycled on and off by 3 triacs (1
each) with arc snubbers across them and there is a relay that cuts the power
to the triac/transformer circuits when the oven is off. Each mag has 2
thermal cutouts, 3 cut off the power to the respective transformer primary
and the other 3 are wired in series and are connected to the logic board
which makes the vacuum fluorescent display show HOT and also causes the oven
to refuse to operate. There is also a thermal fuse in the oven cavity air
discharge duct.

I think I have provided WAY more info than anybody wanted or needed.

"msg" wrote in message
ernet...
Daniel Who Wants to Know wrote:

snip

Yes like my Amana commercial RadarRange which is 4KW in 2.2KW out and has
3 HV magnetrons along with 3 each of the other necessary items (cap,
diode, etc.).

Does this oven somehow injection-lock the magnetrons? Can you describe
the (RF) plumbing?

Michael

In my other post I forgot to mention that Sam already has most of what I
wrote posted on his site somewhere as I sent him the details awhile back.

On Thu, 19 Jun 2008 03:38:43 GMT, "Daniel Who Wants to Know"
wrote:



Each mag has its own waveguide with a rotating antenna at the end that
extends into the oven cavity. 2 of the waveguides are at the top of the
cavity firing down and the third is at the bottom firing up. The HV
transformer primaries are wired so that the top 2 mags fire on the positive
alternation of the AC sine wave and the bottom mag fires on the negative
alternation. The top 2 antennas are driven by a single timer motor with
large plastic gears (complete with timing marks) so that they both are
pointing the same direction at all times as they rotate. The HV
transformers have tapped primaries so that the oven can operate on either
208 or 230 volts with no change in output power. Also there is a small
208-230 volt boost autotransformer that boosts the voltage for the cavity
lamp, cooling blower, and antenna motors when the oven is plugged in to 208.
When the microwave is first plugged in it sits for about 30 seconds to (I
assume) to sense the supplied voltage and frequency so that it uses the
correct taps on the 4 transformers. Oh yeah when the oven is set for less
than 100% power the HV transformers are cycled on and off by 3 triacs (1
each) with arc snubbers across them and there is a relay that cuts the power
to the triac/transformer circuits when the oven is off. Each mag has 2
thermal cutouts, 3 cut off the power to the respective transformer primary
and the other 3 are wired in series and are connected to the logic board
which makes the vacuum fluorescent display show HOT and also causes the oven
to refuse to operate. There is also a thermal fuse in the oven cavity air
discharge duct.

I think I have provided WAY more info than anybody wanted or needed.


Perhaps more info, but intersting info, and appreciated. g

In alt.engineering.electrical Daniel Who Wants to Know wrote:
| wrote in message
| ...
| In alt.engineering.electrical Daniel Who Wants to Know
| wrote:
|
| | Yes like my Amana commercial RadarRange which is 4KW in 2.2KW out and
| has 3
| | HV magnetrons along with 3 each of the other necessary items (cap,
| diode,
| | etc.). It even has a current transformer that tells the control board
| via
| | current draw when the magnetrons are warmed up so that the timer doesn't
| | start counting down until it is actually cooking. It has a standard
| NEMA
| | 6-20 plug on it now and will pop a bag of popcorn in roughly 75 seconds
| | without scorching it. I can tell you it sure beats the hell out of
| regular
| | microwave ovens for most things. The only thing I still use the regular
| one
| | for are items that involve liquids as the Amana tends to make them
| either
| | boil over or boils out all of the water before the food is cooked.
|
| Will it operate on single phase power, like I have in my home?
|
|
| Considering a NEMA 6-20 plug only has the 2 hot prongs plus ground and the
| cord is a 14-3 AWG with one conductor being ground, yes it is single phase.

Don't be so quick to jump to conclusions. The NEMA 6-XX series gets used for
both the 208 volt 120 degree and the 240 volt 180 degree 2-wire connections.
Some devices work on one and not the other. You CAN derive three phase from
one and not the other. A motor could be wired to use that angular difference
(with the neutral) to achieve a motor starting direction instead of having a
capacitor to change the angle on a shaded pole.

Also, if the supply is 208 volts then the maximum power available is 4157 watts
(3326 under the 80% rule), whereas with 240 volts it is 4800 (3840 under 80%).

240 volts is a 15.47% increase over 208 volts. 277 volts is a 15.47% increase
over 240 volts. Can either of those be substituted for 240 volts easily?

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|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
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wrote in message
...

Don't be so quick to jump to conclusions. The NEMA 6-XX series gets used
for
both the 208 volt 120 degree and the 240 volt 180 degree 2-wire
connections.
Some devices work on one and not the other. You CAN derive three phase
from
one and not the other. A motor could be wired to use that angular
difference
(with the neutral) to achieve a motor starting direction instead of having
a
capacitor to change the angle on a shaded pole.

Also, if the supply is 208 volts then the maximum power available is 4157
watts
(3326 under the 80% rule), whereas with 240 volts it is 4800 (3840 under
80%).

240 volts is a 15.47% increase over 208 volts. 277 volts is a 15.47%
increase
over 240 volts. Can either of those be substituted for 240 volts easily?

--
|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 this specific application the third prong is used only as a chassis
ground connection as everything including the light bulb is 230V. Also I am
no expert here but I think intermittent loads can exceed the 80% rule hence
the 14 gauge cord which would normally only be good for 15 amps but is
protected by a 20 amp fuse inside the oven and a 20 amp double pole circuit
breaker in the service panel. The NM-B (Romex) I used is 12-3 with ground
and has the white neutral conductor simply capped but not connected at
either end.

Daniel Who Wants to Know wrote:

Also I am
no expert here but I think intermittent loads can exceed the 80% rule hence
the 14 gauge cord which would normally only be good for 15 amps but is
protected by a 20 amp fuse inside the oven and a 20 amp double pole circuit
breaker in the service panel.
..
The US NEC allows about any cord of 2 conductors (not including ground)
to be used at 18A. Most (all?) cords with type starting H (hard use) can
be used at 20A.

The 80% rule is for continuous loads - over 3 hours.

--
bud--

In alt.engineering.electrical bud-- wrote:
| Daniel Who Wants to Know wrote:
|
| Also I am
| no expert here but I think intermittent loads can exceed the 80% rule hence
| the 14 gauge cord which would normally only be good for 15 amps but is
| protected by a 20 amp fuse inside the oven and a 20 amp double pole circuit
| breaker in the service panel.
| .
| The US NEC allows about any cord of 2 conductors (not including ground)
| to be used at 18A. Most (all?) cords with type starting H (hard use) can
| be used at 20A.
|
| The 80% rule is for continuous loads - over 3 hours.

Like a computer?

--
|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) |

"bud--" wrote in message
.. .
Daniel Who Wants to Know wrote:

Also I am no expert here but I think intermittent loads can exceed the
80% rule hence the 14 gauge cord which would normally only be good for 15
amps but is protected by a 20 amp fuse inside the oven and a 20 amp
double pole circuit breaker in the service panel.
.
The US NEC allows about any cord of 2 conductors (not including ground) to
be used at 18A. Most (all?) cords with type starting H (hard use) can be
used at 20A.

"for short period and with limited lenght"


The 80% rule is for continuous loads - over 3 hours.

--
bud--

A. K. SEPUT wrote:
"bud--" wrote in message
.. .
Daniel Who Wants to Know wrote:
Also I am no expert here but I think intermittent loads can exceed the
80% rule hence the 14 gauge cord which would normally only be good for 15
amps but is protected by a 20 amp fuse inside the oven and a 20 amp
double pole circuit breaker in the service panel.
.
The US NEC allows about any cord of 2 conductors (not including ground) to
be used at 18A. Most (all?) cords with type starting H (hard use) can be
used at 20A.

"for short period and with limited lenght"
..
I see neither limitation in the US NEC.
..
The 80% rule is for continuous loads - over 3 hours.


--
bud--

? "bud--" ?????? ??? ??????
...
A. K. SEPUT wrote:
"bud--" wrote in message
.. .
Daniel Who Wants to Know wrote:
Also I am no expert here but I think intermittent loads can exceed the
80% rule hence the 14 gauge cord which would normally only be good for
15 amps but is protected by a 20 amp fuse inside the oven and a 20 amp
double pole circuit breaker in the service panel.
.
The US NEC allows about any cord of 2 conductors (not including ground)
to be used at 18A. Most (all?) cords with type starting H (hard use) can
be used at 20A.

"for short period and with limited lenght"
.
I see neither limitation in the US NEC.
.
The 80% rule is for continuous loads - over 3 hours.


--
Correct. #14 is the same as Europe's 4 mm^2-which we usually use here in
Greece for the regular, 4 kW hot water heaters. It's rated for 20 A
continuous duty when in a conduit with 1 live conductor (IIRC), we don't
have extensions in that gauge. We usually protect it with an 20 A circuit
breaker (single pole, aka automatic fuse) and a double pole circuit breaker
(aka switch) which is not automatic, just to turn on off the water heater.
There are 3kW heating elements, too, for older installations, which are
quite incapable of sustaining a 4kW load.



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