Surge Protector

[Franc Zabkar]

On Tue, 24 Jul 2007 09:02:39 -0700, w_tom <w_tom1@usa.net> put finger
to keyboard and composed:

On Jul 23, 6:01 am, Franc Zabkar <fzab...@iinternode.on.net> wrote:
On Fri, 20 Jul 2007 06:39:35 -0700,w_tom<w_t...@usa.net> put finger

You cannot seriously claim that a figure of 3% or 5% is significant.
It amounts to *nothing*. It is certainly not a valid reason to choose
a higher energy MOV over a lower energy one. It makes about as much
sense as choosing a 5W zener over a 400mW zener when the circuit
dissipation calls for 100mW. The benefits of a larger MOV are an
ability to withstand a larger surge, and an ability to withstand more
surges in the same time. The latter is reflected in the average power
rating.

Again the point is being avoided - a point directly traceable to
Tim's original question. Franc claims shunt mode protectors work by
absorbing surges. In each case, a better protector absorbs less
energy. MOVs with more joules absorb less energy.

A reduction of 3% (your numbers) is insignificant.

Replacing MOVs
with avalanche diodes absorb even less energy. Using a gas discharge
tube (as was the standard solution almost 100 years ago) absorbs even
less energy,

E = Vp x Ip x dt for *all* shunt mode protectors.

Absorbing less energy is what a shunt mode protector
does - equivalent to what a wire does.

What will happen if you place a wire across a mains supply?

Energy is shunted (diverted,
clamped, connected) elsewhere. That 'elsewhere' is earth ground.

This is the IV characteristic of a perfect shunt mode protector:

I
| +I ^
| |
| |
-V ______0_____| +V ---> V
|
|
|
| -I

Nowhere is the resistance (R=V/I) of the protector equal to zero.


This is the IV characteristic of a perfect wire, ie one with zero
resistance:

I
| +I ^
| |
| |
|V=0 ---> V
|
|
|
| -I

Bud so dislikes this reality because his protectors don't have a low
impedance earthing connection. Why is earthing THE most critical
component in a shunt mode 'system'?

Earthing is irrelevant to a shunt mode system, unless the surge/spike
is being shunted to earth.

An MOV, et al becomes as
conductive as possible. A surge is shunted (clamped, diverted) to
earth ground. Earth dissipates the surge - not a protector. An MOV
that shunts 20 or 30 times more energy to earth (than is absorbed) is
a best protector for the dollar.

Energy does *not* pass mysteriously through a MOV on its way to earth.

MOV does not protect by absorbing surge energy. MOV protects by
shunting that energy elsewhere - into earth.

Explain how a shunt mode protector (eg transorb) connected across the
generator terminals in an airplane utilises an earth connection?

The bottom line about surge protection:
Only component required in a surge protection system is earth ground.

A two-wire appliance has no earth ground other than the earth-neutral
bond in a MEN system. A surge suppressor between A-N is required
because only one end of a common mode surge entering the premises is
shunted to ground at the meter box.

Either a surge is connected directly to earth OR we install an MOV
type protector to make a temporary earthing connection. Earthing
electrode is the 'protection'. 'Protector' is either a hard wire
(cable TV or satellite dish) or a 'whole house' type protector (for
telephone or AC electric).

MOV and wire only absorb energy because each is not perfect.

A *perfect* shunt mode protector *always* absorbs energy. That's in
the nature of its design. Please place an X on the IV characteristic
curve that I have drawn above, showing any point where the absorbed
energy is zero.

Both
absorb trivial energy to shunt massive energy elsewhere. Both become
even better protectors when they absorb less energy. Franc - that is
the point. Better protectors in every case absorb less energy.

Yes, a better shunt mode protector will have a vertical IV
characteristic, not one shaped like an ice hockey stick. And yes, it
will absorb less energy. But a 20mm MOV will only absorb 3% less
energy (your numbers) than a 7mm MOV.

More
joules in an MOV means it absorbs less energy - especially when the
MOV is so grossly undersized as to operate at the end of that hock
stick upswing. Why do you keep trying to claim a better protector
will absorb more surge energy? Why do you keep arguing irrelevance?

I have *never* claimed that. I have always said that a bigger MOV will
only absorb about 3-5% less energy than a smaller one. The bigger MOV
is better because it will sustain larger surges without damage, and
because it can sustain more surges, not because it can reduce the
impact of the same surge current by a mere 5%.

Tim asked whether a surge protector was recommended. Yes, but one
that earths surges. One that is sufficiently size so as to be a
better conductor - not create these scary pictures:
http://www.hanford.gov/rl/?page=556&parent=554
http://www.westwhitelandfire.com/Articles/Surge%20Protectors.pdf
http://www.ddxg.net/old/surge_protectors.htm
http://www.zerosurge.com/HTML/movs.html

Since an MOV operates by shunting (absorbing less energy), then the
protector will only be as effective as its earth ground. Earth is
where energy is absorbed. No earth ground means an MOV has nothing to
shunt to - provides no effective protection. Tim should install a
protector that actually earths surges - by becoming as conductive as
is practicable.

A MOV is only interested in the potential between its two terminals.
It doesn't care where the surge current goes - it just attempts to
maintain its terminal voltage as low as possible.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[bud--]

w_tom wrote:


I will try not to repeat what Franc has just posted - I agree with him
completely.

Bud so dislikes this reality because his protectors don't have a low
impedance earthing connection. Why is earthing THE most critical
component in a shunt mode 'system'?

The elephant in the room is w_’s religious belief in earthing.
Apparently w_ can not consider that the intrinsic action of a MOV is
*clamping*, because it threatens his religious belief in earthing, which
requires shunting.

But the IEEE guide explains plug-in suppressors work by CLAMPING the
voltage on all wires (signal and power) to the common ground at the
suppressor. Plug-in suppressors do not work primarily by earthing (or
shunting or absorbing). The guide explains earthing occurs elsewhere.
(Read the guide starting pdf page 40).
http://omegaps.com/Lightning%20Guide_FINALpublishedversion_May051.pdf

MOV does not protect by absorbing surge energy. MOV protects by
shunting that energy elsewhere - into earth.

Religious belief in earthing #2.

Still not explained by w_ - for a MOV connected across a relay coil,
where is energy shunted to. (And then there is Franc’s airplane.)

And of course, plug-in suppressors do not work primarily by shunting - a
major violation for w_ (but not for the IEEE or anyone else). They do
not work primarily by absorbing either.

The bottom line about surge protection:
Only component required in a surge protection system is earth ground.
Either a surge is connected directly to earth OR we install an MOV
type protector to make a temporary earthing connection. Earthing
electrode is the 'protection'.

The religious belief in earthing - #3.

Tim asked whether a surge protector was recommended. Yes, but one
that earths surges. One that is sufficiently size so as to be a
better conductor - not create these scary pictures:
http://www.hanford.gov/rl/?page=556&parent=554

w_ can't understand his own hanford link. It is about "some older
model" power strips and says overheating was fixed in the US with a
revision to UL1449 that requires thermal disconnects. That was 1998.
Perhaps w_ thinks you are not as smart in Australia?

Since an MOV operates by shunting (absorbing less energy), then the
protector will only be as effective as its earth ground. Earth is
where energy is absorbed. No earth ground means an MOV has nothing to
shunt to - provides no effective protection.

Religious belief in earthing #4?

Because w_ is evangelical in his belief in earthing, he uses google
groups to search for “surge” to spread his beliefs. Among his primary
beliefs is that plug-in suppressors can’t possibly work.
Perhaps w_’s nonsense about MOVs is an attempt at a ‘scientific’
attack on plug-in suppressors. w_ knows that in a direct attack he will
get hammered.

Tim should install a
protector that actually earths surges - by becoming as conductive as
is practicable.

Tim should read reliable sources for information, like the IEEE and NIST
guides.

Both guides say plug-in suppressors are effective.

w_ has never produced a link to a source that says plug-in suppressors
are NOT effective. Or that agrees with his nonsense about MOVs.

Never explained by w_:
- Why do the only 2 examples of protection in the IEEE guide use plug-
in suppressors?
- Why does the NIST guide says plug-in suppressors are "the easiest
solution"?
- Where is energy shunted to for a MOV connected across a relay coil?

--
bud--