Question about MOV's

[Noah]

Probably a stupid question, but why aren't MOV's standard in all
electrical appliances like amplifiers and computer PSUs?
They are found in most power boards these days to obviously protect
equipment from being destroyed.

 

[Trevor Wilson]

Probably a stupid question, but why aren't MOV's standard in all
electrical appliances like amplifiers and computer PSUs?
They are found in most power boards these days to obviously protect
equipment from being destroyed.

**Because:
* They cost money.
* They cannot provide 100% protection. They can only ever provide a measure
of protection.
* They may not be necessary.

 

[Noah]

**Because:
* They cost money.

What? A couple of bucks.

* They cannot provide 100% protection. They can only ever provide a measure
of protection.

I agree, but tell that to the average consumer thinking surge boards protect the
appliance no matter what.

* They may not be necessary.

Depends on the appliance right?

Thanks for your input

 

[Rod Speed]

Probably a stupid question, but why aren't MOV's standard
in all electrical appliances like amplifiers and computer PSUs?

They are basically.

 

[Trevor Wilson]

What? A couple of bucks.

**Even less than that. A couple of bucks can push a product out of its
target price range. Mass market manufacturers are _very_ tight with Dollars.
I read where an engineer working for Nisssan (Japan) was given a
US$50,000.00 bonus, because he was able to reduce the number (from 7 down to
5) of spot welds to the 'A' pillar of one of their vehicles. Wanna speculate
on how much a spot weld costs? 5c? 2c? Certainly not much more. That is how
competitive mass market companies must be. Every single cent must be
accountable.

I agree, but tell that to the average consumer thinking surge boards protect the
appliance no matter what.

**Then the person suggesting such a thing can be sued, for false
advertising.

Depends on the appliance right?

**Of course.

Thanks for your input

**You're welcome.

 

[Mike Harding]

What? A couple of bucks.

When you're designing for these types of mass production
high volume product you'll try like hell to loose even one
surface mount resistor.

And don't MOVs "wear out" with time and provide a
likely failure component a few years later?

Mike Harding

 

[Arpit]

Well, there are some in all the psus ive taken part.

 

[Rod Speed]

Well, there are some in all the psus ive taken part.

Me too.

 

[Rod Speed]

First identify which transient is to be protected from.

Nope, makes more sense to have the MOVs anyway
to protect against the inevitable differential mode
transients when they are so cheap.

MOVs inside the appliance are for differential mode transients.

Which are in fact BY FAR the most commonly seen.

But for the larger and more destructive common mode
transients, MOVs inside the appliance would be useless.

Not useless against the by far the more common
differential mode transients tho, so well worth
designing in from the start, as most designs do.

MOVs are quite cheap - on the order of $0.10 for a manufacturer.

So it makes a lot of sense to include them.
If only to reduce the warranty claims.

But then if the appliance already has galvanic isolation
for 1000 or more volts, then what advantage is an MOV?

For the differential mode transients, stupid.

Common mode transient that can approach 6,000 volts, the
MOV has an important contribution. However to be effective
for common mode transients, the MOV must make a less than
3 meter connection to earth ground. What do common mode
transients seek? Earth ground. Just no way for an MOV inside
an appliance to effectively earth a common mode transient.

Got SFA to do with whether MOVs are useful for
differential mode transients, stupid. Which might just be
why the manufacturer includes them in any decent design.

Protection is more than just one component.

Got SFA to do with whether MOVs are useful for
differential mode transients, stupid. Which might just be
why the manufacturer includes them in any decent design.

Protection is a 'system' where even
wire becomes an electronic component.

Got SFA to do with whether MOVs are useful for
differential mode transients, stupid. Which might just be
why the manufacturer includes them in any decent design.

MOVs can be effective in certain locations depending on the
type of transient and what inside the appliance requires protection.

Duh. Which might just be why the manufacturer includes them in
any decent design that includes more than just passive resistance
devices which dont care about differential mode transients.

 

[Richard Freeman]

Probably a stupid question, but why aren't MOV's standard in all
electrical appliances like amplifiers and computer PSUs?
They are found in most power boards these days to obviously protect
equipment from being destroyed.

They pretty well are in equipment that can be protected by them

Q Why are external Surge arrestors sold then ? I hear you ask
A well because people can make money from selling them of course

Q are external Surge arrestors useful ?
A nope not usually most Lightning damage comes into equipment via Aerials,
Phone lines etc

Regards
Richard Freeman

 

[The real Andy]

They pretty well are in equipment that can be protected by them

Q Why are external Surge arrestors sold then ? I hear you ask
A well because people can make money from selling them of course

Q are external Surge arrestors useful ?
A nope not usually most Lightning damage comes into equipment via Aerials,
Phone lines etc

Lightning strikes are a different story. For decent protection against
lightning stikes you will need to invest significant cash, which is not
viable for consumer products. I think these days the telco industries
doesn't even try to arrest surges, rather they let the gear float up to the
stike voltage..

 

[Brian Goldsmith]

Q are external Surge arrestors useful ?
A nope not usually most Lightning damage comes into equipment via Aerials,
Phone lines etc

Lightning strikes are a different story. For decent protection against
lightning stikes you will need to invest significant cash, which is not
viable for consumer products. I think these days the telco industries
doesn't even try to arrest surges, rather they let the gear float up to
the
stike voltage..


**** Oh how the mind boggles!!!!!Do you seriously belive that the POTS
"floats"up to the MVs of a lightning strike? You moron!
Brian Goldsmith.

 

[Rod Speed]

We don't arrest surges. We do as Ben Franklin demonstrated
in 1752. Lightning would damage church steeples. What does
lightning seek? Earth ground. Franklin simply diverted
lightning to earth with lightning rods.

No difference today. Lightning enters via church steeples,
aerials, or all those incoming utilities. Same protection. A
surge protector is not surge protection. Surge protection is
earth ground - as even Franklin demonstrated. Any incoming
wire must make a permanent or temporary connection to earth
ground - to avoid appliance surge damage. Utilities such as
CATV and satellite dish are earthed directly. AC electric and
telephone need something to make the temporary connection.
That is called a surge protector.

Surge protector alone does not make a protection 'system'.
Earth ground is the most critical 'system' component. But
that distance from each incoming wire to earth ground is also
an electronic component. To be effective, the surge protector
must make a less than 3 meter connection (and other
requirements) to central earth ground.

Surge protectors are simple science. The art is earthing.
However many have given up learning how surge protection
always is effective from the direct strike. Many instead buy
plug-in protector that do not even claim to provide direct
strike protection. To sell their products, they forget to
mention which type of surge the protector is designed for AND
avoid all mention of critical earthing.

Previously posted were two types of transients - common and
differential mode. Destructive differential mode transient
all but do not exist. The typically destructive surge is
common mode. It typically occurs once every 8 years, but it
is that destructive as to make effective protection
necessary. Ineffective protection is quickly identified - no
dedicated connection to earth ground AND avoids all discussion
about earthing.

The local telco computer switch connects to overhead wires
everywhere in town. Does it shut down for thunderstorms? Of
course not. So why is it not damaged every year? Because
effective protection has been proven since the 1930s.
Electronics atop the Empire State Building and WTC were struck
25 and 40 times per year without damage. Effective protection
is that well proven. But surge protection is earth ground -
not some fancy overpriced plug-in device. No earth ground
means no effective protection. MOVs are effective when they
form that less than 3 meter connection to central earth ground
AND are sufficiently sized.

In the US, effective 'whole house' protector for AC
electric costs about $1 per protected appliance.

You can keep spouting this flagrant lie till the
cows come home, changes absolutely nothing.

Effective surge protection is also that inexpensive.

Lie upon lie upon lie.

And its MUCH cheaper to just ensure that your
comprehensive insurance covers that sort of damage.

 

[The real Andy]

Lightning strikes are a different story. For decent protection against
lightning stikes you will need to invest significant cash, which is not
viable for consumer products. I think these days the telco industries
doesn't even try to arrest surges, rather they let the gear float up to
the
stike voltage..


**** Oh how the mind boggles!!!!!Do you seriously belive that the POTS
"floats"up to the MVs of a lightning strike? You moron!
Brian Goldsmith.

Go away you old fool. It is quite clear you are an idiot and have no medern
concepts of electronic theory.

 

[Brian Goldsmith]

Lightning strikes are a different story. For decent protection against
lightning stikes you will need to invest significant cash, which is not
viable for consumer products. I think these days the telco industries
doesn't even try to arrest surges, rather they let the gear float up to
the
stike voltage..


**** Oh how the mind boggles!!!!!Do you seriously belive that the POTS
"floats"up to the MVs of a lightning strike? You moron!
Brian Goldsmith.

Go away you old fool. It is quite clear you are an idiot and have no
medern
concepts of electronic theory.


**** Answer the question ,moron!Do you seriously believe that the POTS
"floats" up to the MVs of a lightning strike?
Brian Goldsmith.

 

[Richard Freeman]

It F'ing well is as you would well know if you worked with a Telco for any
length of Time I have seen Sites that are blown to kingdom come just about
every time a Thunderstorm rolls into Town - DESPITE the best efforts of the
Telco I worked with to provide Lightning protection

You can keep spouting this flagrant lie till the
cows come home, changes absolutely nothing.


Lie upon lie upon lie.

And its MUCH cheaper to just ensure that your
comprehensive insurance covers that sort of damage.

Ahh but you forget or are unaware that mr w_tom makes his living from
selling 'whole house Surge arrestors' and he conveniently forgets to
mention that for effective Earthing to cost $1 per appliance assumes you
have around 10,000 appliances in the house - or by the time you take into
account the cost of land in say Sydney it assumes you have around 300,000
appliances. And will still fail to protect appliances in the event of the
most common form of surge - Lightning entry via other than power cables but
only in an extremely rare event - that of lightning damage via Power mains.

 

[Richard Freeman]

Lightning strikes are a different story. For decent protection against
lightning stikes you will need to invest significant cash, which is not
viable for consumer products. I think these days the telco industries
doesn't even try to arrest surges,

That Generally true for a couple of reasons :

1) Lightning/surge protection is generally useless in the event of a
Lightning strike
2) Inadequate earthing on surge arrestors used on Telco lines (and other
equipment ) can actually cause damage in the event of a Lightning strike due
to EPR (Earth Potential Rise) which is where the Earth voltage can float up
(in the event of a direct strike local EPR can exceed 50,000 Volts) - this
is the same phenomonon that kills cows standing in fields near lightning
strikes.
3) a good (effective) Earth will generally cover in excess of 1/4 an Acre of
ground and cost around $10,000 to install

rather they let the gear float up to
the
stike voltage..


**** Oh how the mind boggles!!!!!Do you seriously belive that the POTS
"floats"up to the MVs of a lightning strike? You moron!
Brian Goldsmith.

Well it floats up until the insulation too something gives - Generally in
the case of a phone line connected to a modem the insulation in the Line
Isolation Tranny and other assorted odds and ends in the modem, usually
mainly at the end of the cable the strike occours at although I have seen
Lightning Travel down 5 Kms of Cable and blow up the equipment Back at the
Telephone exchange. In the case of Lines going via underground cables the
Insulation of the cable gives way as well often with very spectacular
results - But the best thing about underground cables is when the lightning
hits the ground near the cable and the localised EPR blows the shite out of
the insulation and kills equipment at each end of the cable anyway
Regards
Richard Freeman

 

[Rod Speed]

Minimally effective 'whole house' protectors of
greater than 1000 joules sell for less than $50.

Pity that much more than just that is required.

That is less than $1 per effectively protected appliance.

Another lie. Few have 50 appliances plugged in all
the time that need that sort of protection, and the
total cost of $50 is nothing like the real cost anyway.

3) In many locations, a single 3 meter ground rod
is been demonstrated sufficient for effective
earthing of a direct strike - about $9 for the rod.

There's the tiny matter of the connection between that
rod and the 'whole house protector', and the fact that
its completely illegal to install it yourself and isnt a trivial
matter to install even if you choose to flout the law.

Surge protection is that easily installed.

Obvious lie.

Damage demonstrates how little effective
surge protection is actually installed.

Most of us havent had ANY damage over decades.

It makes a hell of a lot more sense to just make sure that
the comprehensive insurance covers that sort of damage
for the very remote possibility that it ever happens.

4) Where damage has been experienced and especially
where lightning damage occurs repeatedly, the human
requires technical assistance in the art of earthing -
because direct lightning strike damage is routinely avoided.

And you wont get that for anything like $50 total cost.

There are many humans who cry "woe is me". As
quitters, they get the lightning damage they deserve.

And there are FAR more mindless Chicken Littles mindlessly
hyperventilating about the sky falling and telling flagrant lies
about the real cost of what they advocate.

They get the obscene gesture they deserve, too.

 

[Richard Freeman]

1) I don't work for any surge protector manufacturer nor sell
these products. If I did sell protectors, then why do I
recommend so many competitor products? Clearly wild
speculation based upon no facts has no merit.

Hmm let see Someone who appears to use Google to search out postings with
the words 'surge', 'Lightning' etc in them and then visits NGs he does not
otherwise post in to sing the praises of 'whole house protection' despite
having his errors pointed out time and time again. I am afraid the only
other explantions for this kind of behaviour are less reptuable than having
a vested commercial interest.
I also note that you merely claim not to sell these products or work for a
surge protection Manufacturer these two claims hardly discount all the
potential forms of commercial self interest you could have. Maybe if you
stated what you did and what you used to do for a living we might believe
you.

2) Minimally effective 'whole house' protectors of greater
than 1000 joules sell for less than $50. That is less than $1
per effectively protected appliance.

Like I said effective Earthing costs more in the order of $10,000 - and I am
talking earthing here I am not talking about cheap shitty MOVs which handle
a monstrous 2000A for the 2.5nS they survive for, I am talking effective
Earthing. The EPR on a typical single Earth stake during a Lightning strike
IS in excess of 50,000 Volts - hardly an effective earth.

3) In many locations, a single 3 meter ground rod is been
demonstrated sufficient for effective earthing of a direct
strike - about $9 for the rod. Of course better grounding
means even better protection. Surge protection is that easily
installed. Damage demonstrates how little effective surge
protection is actually installed.

BS a single 3 meter Earth stake in the event of a Direct strike is woefully
inadequate suffering an EPR in a typical installation in excess of 50,000
Volts in fact in the event of an indirect near strike on say a lightning rod
etc the EPR can travel up the protective earth and look fo rthe far superior
MEN Earth blowing the crap out of any appliance in its path

4) Where damage has been experienced and especially where
lightning damage occurs repeatedly, the human requires
technical assistance in the art of earthing - because direct
lightning strike damage is routinely avoided. There are many
humans who cry "woe is me". As quitters, they get the
lightning damage they deserve.

usually at great cost being multiple earth stakes bonded together and spread
out over an area of 1/4 of an Acre or more.
mains.

 

[Rod Speed]

Hmm let see Someone who appears to use Google to
search out postings with the words 'surge', 'Lightning' etc
in them and then visits NGs he does not otherwise post in
to sing the praises of 'whole house protection' despite having
his errors pointed out time and time again. I am afraid the
only other explantions for this kind of behaviour are less
reptuable than having a vested commercial interest.

Or he's just got one hell of a bee in his bonnet about 'whole house protection'

Rather pathetic, really.

He's also mindless obsessive about
brand name power supplys for PCs too.

Everything points to a substantial problem between the ears.

I also note that you merely claim not to sell these products
or work for a surge protection Manufacturer these two
claims hardly discount all the potential forms of commercial
self interest you could have. Maybe if you stated what you
did and what you used to do for a living we might believe you.

It appears to do nothing but comb usenet for those mentions.

Maybe from its padded cell etc.