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"Sally" <me@anon.net> wrote in message
news:4691e732$1@dnews.tpgi.com.au...
Well, I certainly won't be buying anything from rage audio. The website
link is engineered with similar care...
**Feel free to list all the known examples of where a standard, off the
shelf surge protector has protected equipment. If you want snake oil
products (over-priced surge protectors) then you'll need to shop
elsewhere.
Learn about 'top-posting' and try to refrain from doing so. It is poor
netiquette. Let Google be your friend.
--
Trevor Wilson
www.rageaudio.com.au
--
Posted via a free Usenet account from http://www.teranews.com
On Jul 11, 3:23 am, Franc Zabkar <fzab...@iinternode.on.net> wrote:
...
For example, Belkin's 4-way Surgeboard (the cheapest) boasts the
following specs:
Part # F9A402au2M
Protection: Level 1
Joules: 714J
Maximum Spike Current: 19,500A
Assuming that a 100W incandescent lamp experiences a cold current of
10 times its operating current for 2 mains cycles, then its energy
dissipation would be only 100W x 10 x 20ms x 2 = 40 Joules.
Comparing the two figures (714J vs 40J), is it any wonder that your
lamp failed while your MOV survived?
Your post is based in some assumptions. For example, a lamp
filament absorbs nearer to zero energy when cold. Bulbs fail after
filament gets too hot - vaporizes. Typical surges are microseconds.
Filament never gets hot enough fast enough to increase resistance,
then vaporize.
For example, a 'whole house' protector rated for 50,000 amps will
have wires how large? 2 or 2.5 mm diameter copper. A wire rated for
20 amps constant current is also sufficient to shunt 50,000 amps surge
current because that surge is not constant; typically in
microseconds. Same reason why short transients surges would dissipate
so little energy in a light bulb.
To have sufficient energy to blow a bulb, that current must conduct
longer. Source of higher energy and source of current long enough may
be utility supplied electricity.
Confused is how light bulbs dissipate energy verses what joules
measure for an MOV. Same units measure different parameters.
Joules for MOVs is a measure of how conductive the MOV may be and a
ballpark measurement of its life expectancy (size, pulse width, and
number of transients). Joules for MOVs is equivalent to measuring
gauge of a wire from Ben Franklin lightning rod to earth. If that
wire is too thin, then it will vaporize. If MOV has too few joules,
then it will degrade. MOV vaporizes only when current massively
exceeds what manufacturer intended - well beyond Maximum Permissible
parameters.
More joules in an MOV mean MOV absorbs even less energy. More
joules for a light bulb means a bulb dissipates more energy. For a
constant current, higher joules in an MOV means more conductive; high
joules for a light bulb means less conductive.
Conductivity of a wire is measured in amperes. Conductivity of MOVs
is measured in joules. The difference between wire and MOV: wire does
not degrade with use. MOVs degrade with use. Wires are for
continuous current. MOVs are for rare and short current transients
that are typically measured in microseconds. Whereas necessary wire
size is measured by wire gauge; MOV size is measured by joules and
lamp energy dissipation is measured in joules. Joules for a lamp and
joules for an MOV are measuring two different parameters.
What happens when an MOV is better - more joules? Then it absorbs
even less energy. MOV function is not to absorb energy. It's
function is to shunt (connect, divert, clamp, bond) that electricity
elsewhere.
Suggest you attend to your website links.
"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
One can't expect any more from a cheap imported transister sales person
**Feel free to list all the known examples of where a standard, off theSuggest you attend to your website links.
**I suggest you read this site:Suggest you attend to your website links.
has been acceptable for some time and the weakness of your rebutal does"Sally" <me@anon.net> wrote in message news:469523ee@dnews.tpgi.com.au...
Suggest you attend to your website links.
**I suggest you read this site:
nice sidestep and tap dance you spamming prick , top posting is and
"Sally" <me@anon.net> wrote in message news:469523ee@dnews.tpgi.com.au...
Suggest you attend to your website links.
**I suggest you read this site:
http://linux.sgms-centre.com/misc/netiquette.php
Pay particular attention to the part on 'top-posting'. I realise that you
are (probably) a newbie. NOW is the time to break your bad habits.
I am still awaiting your answer about surge protectors.
--
Trevor Wilson
www.rageaudio.com.au
--
Posted via a free Usenet account from http://www.teranews.com
Yep, looks like www.rageaudio.com.au/ is missing an index.html (and all theHi Trevor
It is a silly question because few people would record and document such an
event (even if they were aware of it). But over 20 years dealing with events
of this kind I would guess I have seen a few hundred successes (and some
failures, with very close or direct strikes). I did not record them because
I didn't then have the pleasure of foreseeing your question. I have the
individual files going back 6 years (Statute of Limitations -- annual
cull -- space problems!) but I am not going to hack through every report and
each file and make a schedule just to prove a point.
BTW, I agree with your point about "cheap off the shelf"; I have never
implied otherwise.
The product has to be properly engineered.
I am not a newbie. The very opposite (active on Usenet since about 1984). I
choose to top post because I believe that regulars prefer it to ploughing
through a whole ream of stuff first. The majority are aware of the context.
Things have changed since that netiquette point was established.
Trevor, your website link does not work -- try it!
Hi Trevor
It is a silly question because few people would record and document such an
event (even if they were aware of it). But over 20 years dealing with events
of this kind I would guess I have seen a few hundred successes (and some
failures, with very close or direct strikes). I did not record them because
I didn't then have the pleasure of foreseeing your question. I have the
individual files going back 6 years (Statute of Limitations -- annual
cull -- space problems!) but I am not going to hack through every report and
each file and make a schedule just to prove a point.
BTW, I agree with your point about "cheap off the shelf"; I have never
implied otherwise.
The product has to be properly engineered.
I am not a newbie. The very opposite (active on Usenet since about 1984). I
choose to top post because I believe that regulars prefer it to ploughing
through a whole ream of stuff first. The majority are aware of the context.
Things have changed since that netiquette point was established.
Trevor, your website link does not work -- try it!
"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:46955df6$0$16315$88260bb3@free.teranews.com...
"Sally" <me@anon.net> wrote in message news:469523ee@dnews.tpgi.com.au...
Suggest you attend to your website links.
**I suggest you read this site:
http://linux.sgms-centre.com/misc/netiquette.php
Pay particular attention to the part on 'top-posting'. I realise that you
are (probably) a newbie. NOW is the time to break your bad habits.
I am still awaiting your answer about surge protectors.
--
Trevor Wilson
www.rageaudio.com.au
--
Posted via a free Usenet account from http://www.teranews.com
Not quite off topic, but it's in the spirit of the contents of this thread
I would have thought that the converse was true. For the first 2 or 3On Jul 11, 3:23 am, Franc Zabkar <fzab...@iinternode.on.net> wrote:
...
For example, Belkin's 4-way Surgeboard (the cheapest) boasts the
following specs:
Part # F9A402au2M
Protection: Level 1
Joules: 714J
Maximum Spike Current: 19,500A
Assuming that a 100W incandescent lamp experiences a cold current of
10 times its operating current for 2 mains cycles, then its energy
dissipation would be only 100W x 10 x 20ms x 2 = 40 Joules.
Comparing the two figures (714J vs 40J), is it any wonder that your
lamp failed while your MOV survived?
Your post is based in some assumptions. For example, a lamp
filament absorbs nearer to zero energy when cold.
I accept that the surge *duration* is only microseconds, but the surgeBulbs fail after
filament gets too hot - vaporizes. Typical surges are microseconds.
Let's assume the surge lasts for 1us and that the current is 1000A. AFilament never gets hot enough fast enough to increase resistance,
then vaporize.
Sorry, but I can't make any sense of this.For example, a 'whole house' protector rated for 50,000 amps will
have wires how large? 2 or 2.5 mm diameter copper. A wire rated for
20 amps constant current is also sufficient to shunt 50,000 amps surge
current because that surge is not constant; typically in
microseconds. Same reason why short transients surges would dissipate
so little energy in a light bulb.
To have sufficient energy to blow a bulb, that current must conduct
longer. Source of higher energy and source of current long enough may
be utility supplied electricity.
Confused is how light bulbs dissipate energy verses what joules
measure for an MOV. Same units measure different parameters.
Joules for MOVs is a measure of how conductive the MOV may be and a
ballpark measurement of its life expectancy (size, pulse width, and
number of transients). Joules for MOVs is equivalent to measuring
gauge of a wire from Ben Franklin lightning rod to earth. If that
wire is too thin, then it will vaporize. If MOV has too few joules,
then it will degrade. MOV vaporizes only when current massively
exceeds what manufacturer intended - well beyond Maximum Permissible
parameters.
More joules in an MOV mean MOV absorbs even less energy. More
joules for a light bulb means a bulb dissipates more energy. For a
constant current, higher joules in an MOV means more conductive; high
joules for a light bulb means less conductive.
Conductivity is something else altogether. You are confusing me byConductivity of a wire is measured in amperes. Conductivity of MOVs
is measured in joules.
I can't see it.The difference between wire and MOV: wire does
not degrade with use. MOVs degrade with use. Wires are for
continuous current. MOVs are for rare and short current transients
that are typically measured in microseconds. Whereas necessary wire
size is measured by wire gauge; MOV size is measured by joules and
lamp energy dissipation is measured in joules. Joules for a lamp and
joules for an MOV are measuring two different parameters.
What happens when an MOV is better - more joules? Then it absorbs
even less energy.
Sure, it shunts the surge *current* through itself in an attempt toMOV function is not to absorb energy. It's
function is to shunt (connect, divert, clamp, bond) that electricity
elsewhere.
Time to study datasheets. Learn what the curves are reporting. HowMore joules in an MOV mean MOV absorbs even less energy. More
joules for a light bulb means a bulb dissipates more energy. For a
constant current, higher joules in an MOV means more conductive; high
joules for a light bulb means less conductive.
Sorry, but I can't make any sense of this.
Conductivity of a wire is measured in amperes. Conductivity of MOVs
is measured in joules.
Conductivity is something else altogether. You are confusing me by
redefining your own terms.
The reason that it makes no sense is that both the filament and theOn Jul 12, 6:38 pm, Franc Zabkar <fzab...@iinternode.on.net> wrote:
More joules in an MOV mean MOV absorbs even less energy. More
joules for a light bulb means a bulb dissipates more energy. For a
constant current, higher joules in an MOV means more conductive; high
joules for a light bulb means less conductive.
Sorry, but I can't make any sense of this.
Resistivity and conductivity refer to an intrinsic property of aConductivity of a wire is measured in amperes. Conductivity of MOVs
is measured in joules.
I still don't see it.Conductivity is something else altogether. You are confusing me by
redefining your own terms.
Time to study datasheets. Learn what the curves are reporting. How
you we make an MOV more conductive? We increase it joules. How do we
make an MOV dissipate less energy? We make it larger - more joules.
It is right there in datasheets.
That makes no sense. Assuming that the MOV has a 275V rating, andAgain, what is the current rating of a 2mm wire? 20 amps? Then why
is that same wire also sufficient for conducting a 50,000 amp surge?
Same reason why a hundred amp surge inside the building does not blow
out filaments. Same reason why an MOV rated for a 2000 amps surge
will dissipate less than 2 watts ...
Can you show me one?... AND why its wire leads are 0.8 mm
diameter. 0.8 mm conducts 2000 amps and does not vaporize? Read
datasheets.
Power = V.I = V x 2000A = 2WattsDo some numbers. What is the resistance of a cold 100 watt bulb?
15 ohms? 300 amps squared times 15 ohms times 30 microseconds is
maybe 40 joules. Well MOVs that are rated at 70 joules must not
dissipate more than 2 watts after a 2000 amp surge.
Because it is a 100W light bulb?Why would the 100
watt light bulb be dissipating any more than 2 watts?
No, the same amount of energy is absorbed, it's just that the biggerBut again, read the MOV datasheet. Even a 0.8 mm wire on that MOV
conducts 2000 amps and does not vaporize.
How do we make a MOV more conductive? We increase its joules. What
makes a protector better? More joules. How much energy does an MOV
dissipate during same a size surge when we increase its joules? Less
energy is absorbed.
No, the amount of energy dissipated in the MOV is determined byAgain, joules that measures MOV performance measures parameters
completely different in a light bulb. Do the numbers. To make a
protector absorb less energy; to make it more conductive - then we
increase its joules.
But the MOV is designed to *clamp* the surge voltage, therefore itWe don't want these shunt mode protectors to absorb any energy.
Energy = V.I.dt.However we make neither perfect conducting MOVs nor perfect conducting
wires. Both MOVs and wires dissipate energy. Better means less
energy dissipated by a wire and by an MOV.
MOVs don't work productively by absorbing surges. MOVs work by
doing what wires also do.
It shunted the 2000A through itself, and clamped the surge voltage toFinally back to that 70 joule MOV. While conducting its maximum
2000 amp surge, it may absorb 70 joules. Meanwhile maybe 2400 joules
from that same 2000 amp surge is being absorbed in earth. 2000 amps
times 40,000 volts times 30 microseconds. 40,000 volts may be across
4 kilometers of earth between the earthed MOV and distant earthborne
charges. That same surge did not dissipate over 1000 joules
destructively inside the building because the 70 joule MOV shunted
energy in 2000 amps elsewhere.
The MOV still clamps the surge to 275V. The rest of the surge voltageHow do we increase energy dissipated in earth? We enlarge that 70
joule MOV to 300 joules. Now the MOV may absorb only 40 joules during
that 2000 amp surge.
- Franc ZabkarThat is even better protection. By increasing
joules, we absorb less energy in the MOV - the MOV has been made more
conductive.
On Thu, 12 Jul 2007 22:57:23 -0700, w_tom <w_t...@usa.net
put finger to keyboard and composed:
The reason that it makes no sense is that both the filament and the
MOV are resistive devices, the difference being that the MOV has a
knee shaped IV characteristic. Below its rated voltage, the MOV's
resistance is extremely high, but above this point the resistance
falls sharply. Nevertheless, both devices still dissipate power
according to the formula P=VxI, where V is the voltage appearing at
the terminals of the device, and I is the current passing through the
device. The energy dissipated during asurgewould be VI.dt.
...
I still don't see it.
The amount of energy that a MOV dissipates would be given by VI.dt,
ie it is determined by the event, not by the device. For example, a
20mm 275V 1000J MOV and a 1m 275V 1MJ MOV (does it exist?)
will both dissipate the same amount of energy when hit by the
samesurge.
...
That makes no sense. Assuming that the MOV has a 275V rating,
and assuming that the duration of thesurgeis 20us, then ...
Power = I.V = 2000A x 275V = 550kW
Energy = P.dt = 550E3 x 20E-6 = 11J
... AND why its wire leads are 0.8 mm diameter. 0.8
mm conducts 2000 amps and does not vaporize?
Read datasheets.
...
Left for you to understand is what the "Transient Power Dissipation"I am troubled that you are posting without reveiwing MOV
datasheets. My posts repeatedly referenced datasheets for good
reason.
http://www.nteinc.com/specs/10to99/pdf/movs.pdf
Review a 2V250. Seventy joules. Conducts 4500 amps. Dissipates
how many watts? Less than 1 watt. Left for you is to get another
number from those datasheets - the maybe 0.8? mm diameter wire
conducts 4500 amps without vaporizing.
The reason is that you clearly don't have a grasp of basic electricalFor reasons defined below, I have intentionally not provided
enough numbers for doing arithmetic.
Your NTE datasheet defines the MOV's energy rating as "the maximumMyths proclaim MOVs protect by absorbing energy.
If the device to be protected can tolerate 300V, say, then all that aIf MOV's purpose
is to absorb energy, then the protector must be a series mode device.
It would connect between appliance and wall receptacle like a switch
or fuse. But MOV protectors are shunt mode devices. MOV connects
just like a light bulb - in parallel.
Here is a Vishay datasheet.Series mode devices block (high resistance) to stop surge current.
Shunt mode devices shunt (short, conduct, clamp, near zero resistance)
to divert current. Clamping means that conductor (the MOV) is better
when resistance is lower. Better shunt mode protector absorbs less
energy.
That's exactly my point, only I would use the term "clamped".Example: light bulb and MOV connect same way in a circuit. But
light bulb conducts current without affecting voltage fed to adjacent
appliance. MOV shunts current so that voltage to the adjacent
appliance is reduced.
That makes no sense. You cannot redefine existing electrical terms toAgain conductivity of a wire is defined in amperes (discussing
siemens is only arguing semantics). Conductivity of an MOV is defined
in joules. That example accurately defined the underlying concept.
See the above examples. I suggest you study those same datasheetsA 20mm 275V 1000J MOV and a 1m 275V 1MJ MOV will not dissipate same
energy when conducting the same surge. But again, study charts in
those datasheets. And that is the point. You are speculating without
first learning the technology. That 1MJ MOV will dissipate less
energy. Saying otherwise means you did not study charts in datasheets
or manufacturer application notes.
You have not understood what the datasheets were telling you. LearnYou also do not know how many watts are dissipated because
datasheets were not read. Speculating without first learning
manufacturer facts which is why I am explaining less with each post.
Your "information" is invalid because you do not understand basicIf confused, then numbers from that datasheet can say why I have
posted in error. Instead you want me to read manufacturer datasheets
and application notes for you? If you need me to do that, then
experience says this thread will 'waste on' forever. Posted are
bottom line facts. If you don't do the work from datasheets, well, I
have already spent too much time explaining what manufacturers have
already written. Your calculations are invalid because you did not
first learn information.
Done and ditto to you.BTW, I intentionally shorted some facts. Each reply says you
ignored what was required - study of charts in manufacturer
datasheets. You did not first consult manufacturer datasheets or
their application notes. Therefore arithmetic, performed without
information from those datasheets, is in error. Repeat again ...
consult those datasheets.
See the examples above. Learn what a "clamp" does.Wire, light bulbs, and MOVs are resistive devices. Using your
logic, then all must do exact same thing. Reality - joules determines
MOV conductivity. As MOV joules increase, the MOV becomes more
conductive, it becomes an even better shunt mode protector, AND it
absorbs less energy.
See the examples above. Learn what a "clamp" does.What happens when a shunt mode protector is even
better? It absorb less energy. You will never understand that
without first learning from those manufacturer charts and application
notes.
See the examples above. Learn the difference between average andRead datasheets before doing any arithmetic. Having first not read,
then you even got watts wrong.
<snip>Here is a Vishay datasheet.
High Surge Suppression Varistors:
http://www.vishay.com/docs/29082/23815825.pdf
I should have said that the surge current used in this example wasYou can also directly compare a 320V 7mm MOV with a 320V 20mm MOV. The
first clamps the surge at 780V while the second clamps it at 740V.
That's hardly any difference at all.
Here is the datasheet for Littlefuse's ZA Varistor Series:I am troubled that you are posting without reveiwing MOV
datasheets. My posts repeatedly referenced datasheets for good
reason.
http://www.nteinc.com/specs/10to99/pdf/movs.pdf
Review a 2V250. Seventy joules. Conducts 4500 amps. Dissipates
how many watts? Less than 1 watt.
Exactly. Now you are starting to grasp why lightning surgesHere is the datasheet for Littlefuse's ZA Varistor Series:
http://www.littelfuse.com/data/en/Data_Sheets/ZA.pdf
Notice the references to *average* power as opposed to *instantaneous*
power.
Exactly. Now you are starting to grasp why lightning surgesHere is the datasheet for Littlefuse's ZA Varistor Series:
http://www.littelfuse.com/data/en/Data_Sheets/ZA.pdf
Notice the references to *average* power as opposed to *instantaneous*
power.
I agree with Franc's posts. w_ is totally off in this branch of theOn Sat, 14 Jul 2007 00:18:37 -0700, w_tom <w_t...@usa.net> put finger
to keyboard and composed:
I am troubled that you are posting without reveiwing MOV
datasheets. My posts repeatedly referenced datasheets for good
reason.
http://www.nteinc.com/specs/10to99/pdf/movs.pdf
Review a 2V250. Seventy joules. Conducts 4500 amps. Dissipates
how many watts? Less than 1 watt. Left for you is to get another
number from those datasheets - the maybe 0.8? mm diameter wire
conducts 4500 amps without vaporizing.
Left for you to understand is what the "Transient Power Dissipation"
figure actually means. In fact it most likely refers to the average
(not instantaneous) power that can be dissipated within the MOV (yes,
*within* the MOV) in response to *repetitive* transients. In other
words, while the instantaneous surge power (watts = joules per second)
can be of the order of hundreds of kilowatts, the "Transient Power
Dissipation" rating is a reflection of the MOV's recovery time.
For example, let's assume that a 20mm MOV has just absorbed a 20us 70J
surge. If it is rated at 600mW, then this means that it can tolerate
0.6 joules per second. Therefore the next transient must not arrive
within 70/0.6 = 117 seconds, ie about 2 minutes.
For reasons defined below, I have intentionally not provided
enough numbers for doing arithmetic.
The reason is that you clearly don't have a grasp of basic electrical
theory.
Myths proclaim MOVs protect by absorbing energy.
Your NTE datasheet defines the MOV's energy rating as "the maximum
electrical energy which can be dissipated *within* the varistor by a
single impulse of 10 x 1000ľs current waveform with continuous voltage
applied".
Voltage numbers provided by Franc for a 320V 7mm and 20mm MOV arehttp://www.vishay.com/docs/29082/23815825.pdf
snip
You can also directly compare a 320V 7mm MOV with a 320V 20mm MOV. The
first clamps the surge at 780V while the second clamps it at 740V.
That's hardly any difference at all.
I should have said that the surge current used in this example was
1000A.