is third transformer hole an earth?

[Arfa Daily]

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghjjbg.e5j.catwheezel@ID-107770.user.individual.net...

On 2008-11-11, Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghja8j.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:
In article <slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

[...]

A system carrying a lot of amps to the load that's drawing it, is no more
or
less dangerous than one that's only carrying a small current, except in
as
much as there is a greater potential for heat failure at connection
points
within that system. A high voltage system, irrespective of how many amps
it
is capable of carrying above a few milliamps, is far more dangerous to a
human, than a low voltage system good for a few hundred amps. Given the
(reasonably) constant resistance of any described path through the human
body, a voltage of a hundred volts with a current availability of as
little
as 50mA, may be enough to kill under the right (wrong!) circumstances.

So a charge of 10kV from walking across a carpet (DC) , or a "non-lethal"
50kV "Tazer" (AC), are more dangerous than a 1kV power line? The danger
from 'High Voltage' power lines comes from the vast amount of current they
can deliver.

You see, there you go getting your apples and oranges mixed up again. A
static charge from a carpet is not lethal to you because it is an extremely
high resistance source. That is the nature of a static charge. No matter
whether it is 1kV, 10kV or 40kV, the source resistance will ensure that only
uA will flow for decimals of a uS. Enough to give you a nasty little crack,
yes, but not enough to come within several orders of magnitude of being
lethal. The same applies to the taser. It is designed to not be able to
supply enough current (theoretically) to be lethal. However, its aim is to
incapacitate by disrupting nerve activity and causing extreme pain. To do
this, the charge is applied to the receiving body in multiple short-duration
pulses. In some cases, this has proven to be fatal, I believe, due to the
length of time that the pulses are delivered for. On the other hand, a high
voltage power line, or even a fairly low voltage household supply, *is*
potentially lethal not because it can deliver huge amounts of amps, but
because the voltage that is present, is sufficient to drive *enough* (mili)
amps from that low resistance source through the conduction path within the
body.

On
the other hand, a low voltage welding supply, will not have enough
voltage
behind it to push enough current through that same path to kill you, even
though that supply is good for 200 amps or more.

What voltage does a 'low voltage' welder operate at? Don't they use
capacitors to raise the supply voltage to at least 40kV? Or can welding
really happen at 12V?

Yes, arc welding can occur at 12v and, in fact, at lower voltages than this,
although there are many different methods these days of generating and
controlling the welding arc, though none that operate by charging caps to
the sorts of voltages that you are talking about, as far as I am aware. In
general, arc welding is a high current rather than high voltage system. Spot
welders sometimes work by charging very large capacitors to low voltages.
The reason that the low voltage arc welder is not capable of killing you,
any more than a car battery can, is because although both are extremely low
internal resistance sources, and hence capable of supplying large amounts of
current to a low resistance load, the human body is a much higher resistance
load, so the 12v is not capable of pushing enough miliamps through that
path, to cause electrocution - or even electric shock.

As far as your contention that a transformer isolated supply is only safe
with double insulated equipment, that simply isn't true. The only way
that
you can drive current through the body from such an isolation
transformer,
is to hang yourself across both output terminals. Either terminal to
ground
will present no electric shock hazard at all.

Arfa

Sounds too good to be true.

Well, if you understood the principles of isolation transformers, which as
well as being used on building sites for obvious reasons, are also to be
found in every professional electronics workshop, to render safe, the need
to work on live equipment employing such potentially lethal nasties, as
switch mode power supplies, then you would know that it isn't too good to be
true - it simply *is* true. Sketch it down on a piece of paper then have a
good think about it.

Arfa

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~

 

[Arfa Daily]

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghjjuo.e5j.catwheezel@ID-107770.user.individual.net...

On 2008-11-11, Peter Hucker <none@spam.com> wrote:
On Mon, 10 Nov 2008 21:48:40 -0000, Whiskers <catwheezel@operamail.com
wrote:

On 2008-11-10, Peter Hucker <none@spam.com> wrote:
On Sat, 08 Nov 2008 22:16:47 -0000, Whiskers <catwheezel@operamail.com
wrote:
On 2008-11-08, catchme <someone@somewhere.net> wrote:
john downie2 wrote:

[...]

- but it isn't the Watts that really
hurt, or even the Volts; it's the Amps you really need to be careful
with.

It's both. 1 billion amps at 0.5 volts definitely won't do you any harm
- mainly because you have too much resistance to conduct 1 billion amps
without a much bigger voltage. I'd actually go for the watts being the
best measure of danger (but you have to take into account how many watts
you will dissipate, not how many are available). I can draw 5kW off a
decent car battery into an invertor to power mains appliances, but if I
touch the two terminals, I feel nothing, and I certainly don't dissiapte
5kW!

[...]

You can touch the 12V battery terminals reasonably safely, but don't try
it with the 240V terminals. That voltage is well in excess of the body's
50V limit for being a non-conductor, and the battery can deliver plenty of
Amps to be lethal. It isn't the 240V that kill, it's the 21A.

This is unmitigated nonsense. You clearly have little understanding of how
the terms that you are bandying about, relate to one another, and more
importantly, to current flow within the human body. I don't mean to be
offensive, but there's a good old phrase which goes something like -

"When the hole that you're digging gets too deep to climb out of, stop ... "

'Nuff said, I think.

Arfa

Turning fresh meat into smoke and ash can dissipate a great many Watts.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~

 

[Whiskers]

On 2008-11-12, Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghjjbg.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-11, Arfa Daily <arfa.daily@ntlworld.com> wrote:
"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghja8j.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:
In article <slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

[...]

A system carrying a lot of amps to the load that's drawing it, is no more
or
less dangerous than one that's only carrying a small current, except in
as
much as there is a greater potential for heat failure at connection
points
within that system. A high voltage system, irrespective of how many amps
it
is capable of carrying above a few milliamps, is far more dangerous to a
human, than a low voltage system good for a few hundred amps. Given the
(reasonably) constant resistance of any described path through the human
body, a voltage of a hundred volts with a current availability of as
little
as 50mA, may be enough to kill under the right (wrong!) circumstances.

So a charge of 10kV from walking across a carpet (DC) , or a "non-lethal"
50kV "Tazer" (AC), are more dangerous than a 1kV power line? The danger
from 'High Voltage' power lines comes from the vast amount of current they
can deliver.

You see, there you go getting your apples and oranges mixed up again. A
static charge from a carpet is not lethal to you because it is an extremely
high resistance source. That is the nature of a static charge. No matter
whether it is 1kV, 10kV or 40kV, the source resistance will ensure that only
uA will flow for decimals of a uS. Enough to give you a nasty little crack,
yes, but not enough to come within several orders of magnitude of being
lethal. The same applies to the taser. It is designed to not be able to
supply enough current (theoretically) to be lethal. However, its aim is to
incapacitate by disrupting nerve activity and causing extreme pain. To do
this, the charge is applied to the receiving body in multiple short-duration
pulses. In some cases, this has proven to be fatal, I believe, due to the
length of time that the pulses are delivered for. On the other hand, a high
voltage power line, or even a fairly low voltage household supply, *is*
potentially lethal not because it can deliver huge amounts of amps, but
because the voltage that is present, is sufficient to drive *enough* (mili)
amps from that low resistance source through the conduction path within the
body.

Precisely; it isn't the voltage that's lethal, it's the current. If the
current isn't available, the voltage is pretty harmless. High-voltage
mains power lines carry a /lot/ of current, whereas high-voltage 'Tazers'
don't.

On
the other hand, a low voltage welding supply, will not have enough
voltage
behind it to push enough current through that same path to kill you, even
though that supply is good for 200 amps or more.

What voltage does a 'low voltage' welder operate at? Don't they use
capacitors to raise the supply voltage to at least 40kV? Or can welding
really happen at 12V?

Yes, arc welding can occur at 12v and, in fact, at lower voltages than this,
although there are many different methods these days of generating and
controlling the welding arc, though none that operate by charging caps to
the sorts of voltages that you are talking about, as far as I am aware. In
general, arc welding is a high current rather than high voltage system. Spot
welders sometimes work by charging very large capacitors to low voltages.
The reason that the low voltage arc welder is not capable of killing you,
any more than a car battery can, is because although both are extremely low
internal resistance sources, and hence capable of supplying large amounts of
current to a low resistance load, the human body is a much higher resistance
load, so the 12v is not capable of pushing enough miliamps through that
path, to cause electrocution - or even electric shock.

OK, I'm not familiar with arc welding, and I'm surprised that 12V is
enough to strike an arc. But your comment that it is the high current
that matters for creating a weld, rather supports my contention that
current is more dangerous than voltage.

Electron beam welding (which you probaby won't find happening in a garden
shed or on a building site) requires many thousand volts, but only a small
current (less than 1A).

The only welding I've ever done myself, involved a coke-burning forge and
a heavy hammer.

As far as your contention that a transformer isolated supply is only safe
with double insulated equipment, that simply isn't true. The only way
that
you can drive current through the body from such an isolation
transformer,
is to hang yourself across both output terminals. Either terminal to
ground
will present no electric shock hazard at all.

Arfa

Sounds too good to be true.

Well, if you understood the principles of isolation transformers, which as
well as being used on building sites for obvious reasons, are also to be
found in every professional electronics workshop, to render safe, the need
to work on live equipment employing such potentially lethal nasties, as
switch mode power supplies, then you would know that it isn't too good to be
true - it simply *is* true. Sketch it down on a piece of paper then have a
good think about it.

Arfa

The only 'isolation transformers' I've come across, are earthed - and
either have an output restricted to 50V or less (that threshold at which
the human body's resistance drops substantially) or provide a good earth
connection for the appliance. An isolation transformer /does/ disconnect
the connection that exists between the power station and the ground and is
carried by the 'live' or 'hot' cable, but that is /not/ the same as the
safety 'earth' connection which is meant to provide a relatively safe
return path in case exposed metal parts of the appliance accidentally
become connected to the power supply.

The 'earth' connection provided by an 'isolation transformer' to the
appliances running off it, may be arranged to effectively create a
'short-circuit' on the output windings of the transformer if any current
flows through it, and that should trigger the safety cut-off (probably a
'residual current device'). Or the 'earth' connection will pass straight
through to the same 'earth' as the mains supply provides.

A double-insulated appliance has no exposed metal parts that can become
connected to the power supply, and that's why they are permitted to be
used with no 'earth'.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~

 

[Arfa Daily]

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghlo20.bmt.catwheezel@ID-107770.user.individual.net...

On 2008-11-12, Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghjjbg.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-11, Arfa Daily <arfa.daily@ntlworld.com> wrote:
"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghja8j.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:
In article <slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

[...]

A system carrying a lot of amps to the load that's drawing it, is no
more
or
less dangerous than one that's only carrying a small current, except in
as
much as there is a greater potential for heat failure at connection
points
within that system. A high voltage system, irrespective of how many
amps
it
is capable of carrying above a few milliamps, is far more dangerous to
a
human, than a low voltage system good for a few hundred amps. Given the
(reasonably) constant resistance of any described path through the
human
body, a voltage of a hundred volts with a current availability of as
little
as 50mA, may be enough to kill under the right (wrong!) circumstances.

So a charge of 10kV from walking across a carpet (DC) , or a
"non-lethal"
50kV "Tazer" (AC), are more dangerous than a 1kV power line? The danger
from 'High Voltage' power lines comes from the vast amount of current
they
can deliver.

You see, there you go getting your apples and oranges mixed up again. A
static charge from a carpet is not lethal to you because it is an
extremely
high resistance source. That is the nature of a static charge. No matter
whether it is 1kV, 10kV or 40kV, the source resistance will ensure that
only
uA will flow for decimals of a uS. Enough to give you a nasty little
crack,
yes, but not enough to come within several orders of magnitude of being
lethal. The same applies to the taser. It is designed to not be able to
supply enough current (theoretically) to be lethal. However, its aim is
to
incapacitate by disrupting nerve activity and causing extreme pain. To do
this, the charge is applied to the receiving body in multiple
short-duration
pulses. In some cases, this has proven to be fatal, I believe, due to the
length of time that the pulses are delivered for. On the other hand, a
high
voltage power line, or even a fairly low voltage household supply, *is*
potentially lethal not because it can deliver huge amounts of amps, but
because the voltage that is present, is sufficient to drive *enough*
(mili)
amps from that low resistance source through the conduction path within
the
body.

Precisely; it isn't the voltage that's lethal, it's the current. If the
current isn't available, the voltage is pretty harmless. High-voltage
mains power lines carry a /lot/ of current, whereas high-voltage 'Tazers'
don't.

On
the other hand, a low voltage welding supply, will not have enough
voltage
behind it to push enough current through that same path to kill you,
even
though that supply is good for 200 amps or more.

What voltage does a 'low voltage' welder operate at? Don't they use
capacitors to raise the supply voltage to at least 40kV? Or can welding
really happen at 12V?

Yes, arc welding can occur at 12v and, in fact, at lower voltages than
this,
although there are many different methods these days of generating and
controlling the welding arc, though none that operate by charging caps to
the sorts of voltages that you are talking about, as far as I am aware.
In
general, arc welding is a high current rather than high voltage system.
Spot
welders sometimes work by charging very large capacitors to low voltages.
The reason that the low voltage arc welder is not capable of killing you,
any more than a car battery can, is because although both are extremely
low
internal resistance sources, and hence capable of supplying large amounts
of
current to a low resistance load, the human body is a much higher
resistance
load, so the 12v is not capable of pushing enough miliamps through that
path, to cause electrocution - or even electric shock.

OK, I'm not familiar with arc welding, and I'm surprised that 12V is
enough to strike an arc. But your comment that it is the high current
that matters for creating a weld, rather supports my contention that
current is more dangerous than voltage.

Electron beam welding (which you probaby won't find happening in a garden
shed or on a building site) requires many thousand volts, but only a small
current (less than 1A).

The only welding I've ever done myself, involved a coke-burning forge and
a heavy hammer.

As far as your contention that a transformer isolated supply is only
safe
with double insulated equipment, that simply isn't true. The only way
that
you can drive current through the body from such an isolation
transformer,
is to hang yourself across both output terminals. Either terminal to
ground
will present no electric shock hazard at all.

Arfa

Sounds too good to be true.

Well, if you understood the principles of isolation transformers, which
as
well as being used on building sites for obvious reasons, are also to be
found in every professional electronics workshop, to render safe, the
need
to work on live equipment employing such potentially lethal nasties, as
switch mode power supplies, then you would know that it isn't too good to
be
true - it simply *is* true. Sketch it down on a piece of paper then have
a
good think about it.

Arfa

The only 'isolation transformers' I've come across, are earthed - and
either have an output restricted to 50V or less (that threshold at which
the human body's resistance drops substantially) or provide a good earth
connection for the appliance. An isolation transformer /does/ disconnect
the connection that exists between the power station and the ground and is
carried by the 'live' or 'hot' cable, but that is /not/ the same as the
safety 'earth' connection which is meant to provide a relatively safe
return path in case exposed metal parts of the appliance accidentally
become connected to the power supply.

Neutral and ground are bonded together at the substation

The 'earth' connection provided by an 'isolation transformer' to the
appliances running off it, may be arranged to effectively create a
'short-circuit' on the output windings of the transformer if any current
flows through it, and that should trigger the safety cut-off (probably a
'residual current device'). Or the 'earth' connection will pass straight
through to the same 'earth' as the mains supply provides.

A double-insulated appliance has no exposed metal parts that can become
connected to the power supply, and that's why they are permitted to be
used with no 'earth'.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~

Hmmmm. Your understanding of the principles of ground isolation by use of a
transformer seem very flawed I'm afraid, as also is your knowledge of
electricity distribution schemes, and earth / neutral commonality.

Arfa

 

[Peter Hucker]

On Wed, 12 Nov 2008 13:55:12 -0000, Whiskers <catwheezel@operamail.com> wrote:

On 2008-11-12, Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghjjbg.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-11, Arfa Daily <arfa.daily@ntlworld.com> wrote:
"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghja8j.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:
In article <slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

[...]

A system carrying a lot of amps to the load that's drawing it, is no more
or
less dangerous than one that's only carrying a small current, except in
as
much as there is a greater potential for heat failure at connection
points
within that system. A high voltage system, irrespective of how many amps
it
is capable of carrying above a few milliamps, is far more dangerous to a
human, than a low voltage system good for a few hundred amps. Given the
(reasonably) constant resistance of any described path through the human
body, a voltage of a hundred volts with a current availability of as
little
as 50mA, may be enough to kill under the right (wrong!) circumstances.

So a charge of 10kV from walking across a carpet (DC) , or a "non-lethal"
50kV "Tazer" (AC), are more dangerous than a 1kV power line? The danger
from 'High Voltage' power lines comes from the vast amount of current they
can deliver.

You see, there you go getting your apples and oranges mixed up again. A
static charge from a carpet is not lethal to you because it is an extremely
high resistance source. That is the nature of a static charge. No matter
whether it is 1kV, 10kV or 40kV, the source resistance will ensure that only
uA will flow for decimals of a uS. Enough to give you a nasty little crack,
yes, but not enough to come within several orders of magnitude of being
lethal. The same applies to the taser. It is designed to not be able to
supply enough current (theoretically) to be lethal. However, its aim is to
incapacitate by disrupting nerve activity and causing extreme pain. To do
this, the charge is applied to the receiving body in multiple short-duration
pulses. In some cases, this has proven to be fatal, I believe, due to the
length of time that the pulses are delivered for. On the other hand, a high
voltage power line, or even a fairly low voltage household supply, *is*
potentially lethal not because it can deliver huge amounts of amps, but
because the voltage that is present, is sufficient to drive *enough* (mili)
amps from that low resistance source through the conduction path within the
body.

Precisely; it isn't the voltage that's lethal, it's the current. If the
current isn't available, the voltage is pretty harmless. High-voltage
mains power lines carry a /lot/ of current, whereas high-voltage 'Tazers'
don't.

"Current kills" is a vast oversimplification, as Arfa has explained.


--
http://www.petersparrots.com http://www.insanevideoclips.com http://www.petersphotos.com

To confirm the discontinuation of stopping the startup, click cancel.

 

[ian field]

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghlo20.bmt.catwheezel@ID-107770.user.individual.net...

On 2008-11-12, Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghjjbg.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-11, Arfa Daily <arfa.daily@ntlworld.com> wrote:
"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghja8j.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:
In article <slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

[...]

A system carrying a lot of amps to the load that's drawing it, is no
more
or
less dangerous than one that's only carrying a small current, except in
as
much as there is a greater potential for heat failure at connection
points
within that system. A high voltage system, irrespective of how many
amps
it
is capable of carrying above a few milliamps, is far more dangerous to
a
human, than a low voltage system good for a few hundred amps. Given the
(reasonably) constant resistance of any described path through the
human
body, a voltage of a hundred volts with a current availability of as
little
as 50mA, may be enough to kill under the right (wrong!) circumstances.

So a charge of 10kV from walking across a carpet (DC) , or a
"non-lethal"
50kV "Tazer" (AC), are more dangerous than a 1kV power line? The danger
from 'High Voltage' power lines comes from the vast amount of current
they
can deliver.

You see, there you go getting your apples and oranges mixed up again. A
static charge from a carpet is not lethal to you because it is an
extremely
high resistance source. That is the nature of a static charge. No matter
whether it is 1kV, 10kV or 40kV, the source resistance will ensure that
only
uA will flow for decimals of a uS. Enough to give you a nasty little
crack,
yes, but not enough to come within several orders of magnitude of being
lethal. The same applies to the taser. It is designed to not be able to
supply enough current (theoretically) to be lethal. However, its aim is
to
incapacitate by disrupting nerve activity and causing extreme pain. To do
this, the charge is applied to the receiving body in multiple
short-duration
pulses. In some cases, this has proven to be fatal, I believe, due to the
length of time that the pulses are delivered for. On the other hand, a
high
voltage power line, or even a fairly low voltage household supply, *is*
potentially lethal not because it can deliver huge amounts of amps, but
because the voltage that is present, is sufficient to drive *enough*
(mili)
amps from that low resistance source through the conduction path within
the
body.

Precisely; it isn't the voltage that's lethal, it's the current. If the
current isn't available, the voltage is pretty harmless. High-voltage
mains power lines carry a /lot/ of current, whereas high-voltage 'Tazers'
don't.

In that case you shouldn't have any problem grabbing the high voltage
terminal of a 2kV microwave oven transformer - its only rated for 500mA.

On the bright side, we wouldn't have to put up with you talking complete and
utter bollox.

 

[Meat Plow]

On Wed, 12 Nov 2008 14:50:28 -0000, "Arfa Daily"
<arfa.daily@ntlworld.com>wrote:

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghlo20.bmt.catwheezel@ID-107770.user.individual.net...
On 2008-11-12, Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghjjbg.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-11, Arfa Daily <arfa.daily@ntlworld.com> wrote:
"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghja8j.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:
In article <slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

[...]

A system carrying a lot of amps to the load that's drawing it, is no
more
or
less dangerous than one that's only carrying a small current, except in
as
much as there is a greater potential for heat failure at connection
points
within that system. A high voltage system, irrespective of how many
amps
it
is capable of carrying above a few milliamps, is far more dangerous to
a
human, than a low voltage system good for a few hundred amps. Given the
(reasonably) constant resistance of any described path through the
human
body, a voltage of a hundred volts with a current availability of as
little
as 50mA, may be enough to kill under the right (wrong!) circumstances.

So a charge of 10kV from walking across a carpet (DC) , or a
"non-lethal"
50kV "Tazer" (AC), are more dangerous than a 1kV power line? The danger
from 'High Voltage' power lines comes from the vast amount of current
they
can deliver.

You see, there you go getting your apples and oranges mixed up again. A
static charge from a carpet is not lethal to you because it is an
extremely
high resistance source. That is the nature of a static charge. No matter
whether it is 1kV, 10kV or 40kV, the source resistance will ensure that
only
uA will flow for decimals of a uS. Enough to give you a nasty little
crack,
yes, but not enough to come within several orders of magnitude of being
lethal. The same applies to the taser. It is designed to not be able to
supply enough current (theoretically) to be lethal. However, its aim is
to
incapacitate by disrupting nerve activity and causing extreme pain. To do
this, the charge is applied to the receiving body in multiple
short-duration
pulses. In some cases, this has proven to be fatal, I believe, due to the
length of time that the pulses are delivered for. On the other hand, a
high
voltage power line, or even a fairly low voltage household supply, *is*
potentially lethal not because it can deliver huge amounts of amps, but
because the voltage that is present, is sufficient to drive *enough*
(mili)
amps from that low resistance source through the conduction path within
the
body.

Precisely; it isn't the voltage that's lethal, it's the current. If the
current isn't available, the voltage is pretty harmless. High-voltage
mains power lines carry a /lot/ of current, whereas high-voltage 'Tazers'
don't.

On
the other hand, a low voltage welding supply, will not have enough
voltage
behind it to push enough current through that same path to kill you,
even
though that supply is good for 200 amps or more.

What voltage does a 'low voltage' welder operate at? Don't they use
capacitors to raise the supply voltage to at least 40kV? Or can welding
really happen at 12V?

Yes, arc welding can occur at 12v and, in fact, at lower voltages than
this,
although there are many different methods these days of generating and
controlling the welding arc, though none that operate by charging caps to
the sorts of voltages that you are talking about, as far as I am aware.
In
general, arc welding is a high current rather than high voltage system.
Spot
welders sometimes work by charging very large capacitors to low voltages.
The reason that the low voltage arc welder is not capable of killing you,
any more than a car battery can, is because although both are extremely
low
internal resistance sources, and hence capable of supplying large amounts
of
current to a low resistance load, the human body is a much higher
resistance
load, so the 12v is not capable of pushing enough miliamps through that
path, to cause electrocution - or even electric shock.

OK, I'm not familiar with arc welding, and I'm surprised that 12V is
enough to strike an arc. But your comment that it is the high current
that matters for creating a weld, rather supports my contention that
current is more dangerous than voltage.

Electron beam welding (which you probaby won't find happening in a garden
shed or on a building site) requires many thousand volts, but only a small
current (less than 1A).

The only welding I've ever done myself, involved a coke-burning forge and
a heavy hammer.

As far as your contention that a transformer isolated supply is only
safe
with double insulated equipment, that simply isn't true. The only way
that
you can drive current through the body from such an isolation
transformer,
is to hang yourself across both output terminals. Either terminal to
ground
will present no electric shock hazard at all.

Arfa

Sounds too good to be true.

Well, if you understood the principles of isolation transformers, which
as
well as being used on building sites for obvious reasons, are also to be
found in every professional electronics workshop, to render safe, the
need
to work on live equipment employing such potentially lethal nasties, as
switch mode power supplies, then you would know that it isn't too good to
be
true - it simply *is* true. Sketch it down on a piece of paper then have
a
good think about it.

Arfa

The only 'isolation transformers' I've come across, are earthed - and
either have an output restricted to 50V or less (that threshold at which
the human body's resistance drops substantially) or provide a good earth
connection for the appliance. An isolation transformer /does/ disconnect
the connection that exists between the power station and the ground and is
carried by the 'live' or 'hot' cable, but that is /not/ the same as the
safety 'earth' connection which is meant to provide a relatively safe
return path in case exposed metal parts of the appliance accidentally
become connected to the power supply.


Neutral and ground are bonded together at the substation



The 'earth' connection provided by an 'isolation transformer' to the
appliances running off it, may be arranged to effectively create a
'short-circuit' on the output windings of the transformer if any current
flows through it, and that should trigger the safety cut-off (probably a
'residual current device'). Or the 'earth' connection will pass straight
through to the same 'earth' as the mains supply provides.

A double-insulated appliance has no exposed metal parts that can become
connected to the power supply, and that's why they are permitted to be
used with no 'earth'.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~

Hmmmm. Your understanding of the principles of ground isolation by use of a
transformer seem very flawed I'm afraid, as also is your knowledge of
electricity distribution schemes, and earth / neutral commonality.

Arfa

Whiskers is an idiot from the 24hoursupport.helpdesk newsgroup.
Probably got trolled here by the Hucker idiot.

 

[ian field]

"Meat Plow" <meat@petitmorte.net> wrote in message
news:2bc3rq.btk.19.1@news.alt.net...

On Wed, 12 Nov 2008 14:50:28 -0000, "Arfa Daily"
arfa.daily@ntlworld.com>wrote:


"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghlo20.bmt.catwheezel@ID-107770.user.individual.net...
On 2008-11-12, Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghjjbg.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-11, Arfa Daily <arfa.daily@ntlworld.com> wrote:
"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghja8j.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:
In article
slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

[...]

A system carrying a lot of amps to the load that's drawing it, is no
more
or
less dangerous than one that's only carrying a small current, except
in
as
much as there is a greater potential for heat failure at connection
points
within that system. A high voltage system, irrespective of how many
amps
it
is capable of carrying above a few milliamps, is far more dangerous
to
a
human, than a low voltage system good for a few hundred amps. Given
the
(reasonably) constant resistance of any described path through the
human
body, a voltage of a hundred volts with a current availability of as
little
as 50mA, may be enough to kill under the right (wrong!)
circumstances.

So a charge of 10kV from walking across a carpet (DC) , or a
"non-lethal"
50kV "Tazer" (AC), are more dangerous than a 1kV power line? The
danger
from 'High Voltage' power lines comes from the vast amount of current
they
can deliver.

You see, there you go getting your apples and oranges mixed up again. A
static charge from a carpet is not lethal to you because it is an
extremely
high resistance source. That is the nature of a static charge. No
matter
whether it is 1kV, 10kV or 40kV, the source resistance will ensure that
only
uA will flow for decimals of a uS. Enough to give you a nasty little
crack,
yes, but not enough to come within several orders of magnitude of being
lethal. The same applies to the taser. It is designed to not be able to
supply enough current (theoretically) to be lethal. However, its aim is
to
incapacitate by disrupting nerve activity and causing extreme pain. To
do
this, the charge is applied to the receiving body in multiple
short-duration
pulses. In some cases, this has proven to be fatal, I believe, due to
the
length of time that the pulses are delivered for. On the other hand, a
high
voltage power line, or even a fairly low voltage household supply, *is*
potentially lethal not because it can deliver huge amounts of amps, but
because the voltage that is present, is sufficient to drive *enough*
(mili)
amps from that low resistance source through the conduction path within
the
body.

Precisely; it isn't the voltage that's lethal, it's the current. If the
current isn't available, the voltage is pretty harmless. High-voltage
mains power lines carry a /lot/ of current, whereas high-voltage
'Tazers'
don't.

On
the other hand, a low voltage welding supply, will not have enough
voltage
behind it to push enough current through that same path to kill you,
even
though that supply is good for 200 amps or more.

What voltage does a 'low voltage' welder operate at? Don't they use
capacitors to raise the supply voltage to at least 40kV? Or can
welding
really happen at 12V?

Yes, arc welding can occur at 12v and, in fact, at lower voltages than
this,
although there are many different methods these days of generating and
controlling the welding arc, though none that operate by charging caps
to
the sorts of voltages that you are talking about, as far as I am aware.
In
general, arc welding is a high current rather than high voltage system.
Spot
welders sometimes work by charging very large capacitors to low
voltages.
The reason that the low voltage arc welder is not capable of killing
you,
any more than a car battery can, is because although both are extremely
low
internal resistance sources, and hence capable of supplying large
amounts
of
current to a low resistance load, the human body is a much higher
resistance
load, so the 12v is not capable of pushing enough miliamps through that
path, to cause electrocution - or even electric shock.

OK, I'm not familiar with arc welding, and I'm surprised that 12V is
enough to strike an arc. But your comment that it is the high current
that matters for creating a weld, rather supports my contention that
current is more dangerous than voltage.

Electron beam welding (which you probaby won't find happening in a
garden
shed or on a building site) requires many thousand volts, but only a
small
current (less than 1A).

The only welding I've ever done myself, involved a coke-burning forge
and
a heavy hammer.

As far as your contention that a transformer isolated supply is only
safe
with double insulated equipment, that simply isn't true. The only way
that
you can drive current through the body from such an isolation
transformer,
is to hang yourself across both output terminals. Either terminal to
ground
will present no electric shock hazard at all.

Arfa

Sounds too good to be true.

Well, if you understood the principles of isolation transformers, which
as
well as being used on building sites for obvious reasons, are also to
be
found in every professional electronics workshop, to render safe, the
need
to work on live equipment employing such potentially lethal nasties, as
switch mode power supplies, then you would know that it isn't too good
to
be
true - it simply *is* true. Sketch it down on a piece of paper then
have
a
good think about it.

Arfa

The only 'isolation transformers' I've come across, are earthed - and
either have an output restricted to 50V or less (that threshold at which
the human body's resistance drops substantially) or provide a good earth
connection for the appliance. An isolation transformer /does/
disconnect
the connection that exists between the power station and the ground and
is
carried by the 'live' or 'hot' cable, but that is /not/ the same as the
safety 'earth' connection which is meant to provide a relatively safe
return path in case exposed metal parts of the appliance accidentally
become connected to the power supply.


Neutral and ground are bonded together at the substation



The 'earth' connection provided by an 'isolation transformer' to the
appliances running off it, may be arranged to effectively create a
'short-circuit' on the output windings of the transformer if any current
flows through it, and that should trigger the safety cut-off (probably a
'residual current device'). Or the 'earth' connection will pass
straight
through to the same 'earth' as the mains supply provides.

A double-insulated appliance has no exposed metal parts that can become
connected to the power supply, and that's why they are permitted to be
used with no 'earth'.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~

Hmmmm. Your understanding of the principles of ground isolation by use of
a
transformer seem very flawed I'm afraid, as also is your knowledge of
electricity distribution schemes, and earth / neutral commonality.

Arfa


Whiskers is an idiot from the 24hoursupport.helpdesk newsgroup.
Probably got trolled here by the Hucker idiot.

PHucker usually hangs out on alt.binaries.chatter , I can't recall seeing
whiskers there. PHucker sometimes trolls on the sci.electronics groups -
usually asking stupid questions then criticizing the answers he's given.

 

[Meat Plow]

On Wed, 12 Nov 2008 21:23:05 -0000, "ian field"
<gangprobing.alien@ntlworld.com>wrote:

"Meat Plow" <meat@petitmorte.net> wrote in message
news:2bc3rq.btk.19.1@news.alt.net...
On Wed, 12 Nov 2008 14:50:28 -0000, "Arfa Daily"
arfa.daily@ntlworld.com>wrote:


"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghlo20.bmt.catwheezel@ID-107770.user.individual.net...
On 2008-11-12, Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghjjbg.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-11, Arfa Daily <arfa.daily@ntlworld.com> wrote:
"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghja8j.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:
In article
slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

[...]

A system carrying a lot of amps to the load that's drawing it, is no
more
or
less dangerous than one that's only carrying a small current, except
in
as
much as there is a greater potential for heat failure at connection
points
within that system. A high voltage system, irrespective of how many
amps
it
is capable of carrying above a few milliamps, is far more dangerous
to
a
human, than a low voltage system good for a few hundred amps. Given
the
(reasonably) constant resistance of any described path through the
human
body, a voltage of a hundred volts with a current availability of as
little
as 50mA, may be enough to kill under the right (wrong!)
circumstances.

So a charge of 10kV from walking across a carpet (DC) , or a
"non-lethal"
50kV "Tazer" (AC), are more dangerous than a 1kV power line? The
danger
from 'High Voltage' power lines comes from the vast amount of current
they
can deliver.

You see, there you go getting your apples and oranges mixed up again. A
static charge from a carpet is not lethal to you because it is an
extremely
high resistance source. That is the nature of a static charge. No
matter
whether it is 1kV, 10kV or 40kV, the source resistance will ensure that
only
uA will flow for decimals of a uS. Enough to give you a nasty little
crack,
yes, but not enough to come within several orders of magnitude of being
lethal. The same applies to the taser. It is designed to not be able to
supply enough current (theoretically) to be lethal. However, its aim is
to
incapacitate by disrupting nerve activity and causing extreme pain. To
do
this, the charge is applied to the receiving body in multiple
short-duration
pulses. In some cases, this has proven to be fatal, I believe, due to
the
length of time that the pulses are delivered for. On the other hand, a
high
voltage power line, or even a fairly low voltage household supply, *is*
potentially lethal not because it can deliver huge amounts of amps, but
because the voltage that is present, is sufficient to drive *enough*
(mili)
amps from that low resistance source through the conduction path within
the
body.

Precisely; it isn't the voltage that's lethal, it's the current. If the
current isn't available, the voltage is pretty harmless. High-voltage
mains power lines carry a /lot/ of current, whereas high-voltage
'Tazers'
don't.

On
the other hand, a low voltage welding supply, will not have enough
voltage
behind it to push enough current through that same path to kill you,
even
though that supply is good for 200 amps or more.

What voltage does a 'low voltage' welder operate at? Don't they use
capacitors to raise the supply voltage to at least 40kV? Or can
welding
really happen at 12V?

Yes, arc welding can occur at 12v and, in fact, at lower voltages than
this,
although there are many different methods these days of generating and
controlling the welding arc, though none that operate by charging caps
to
the sorts of voltages that you are talking about, as far as I am aware.
In
general, arc welding is a high current rather than high voltage system.
Spot
welders sometimes work by charging very large capacitors to low
voltages.
The reason that the low voltage arc welder is not capable of killing
you,
any more than a car battery can, is because although both are extremely
low
internal resistance sources, and hence capable of supplying large
amounts
of
current to a low resistance load, the human body is a much higher
resistance
load, so the 12v is not capable of pushing enough miliamps through that
path, to cause electrocution - or even electric shock.

OK, I'm not familiar with arc welding, and I'm surprised that 12V is
enough to strike an arc. But your comment that it is the high current
that matters for creating a weld, rather supports my contention that
current is more dangerous than voltage.

Electron beam welding (which you probaby won't find happening in a
garden
shed or on a building site) requires many thousand volts, but only a
small
current (less than 1A).

The only welding I've ever done myself, involved a coke-burning forge
and
a heavy hammer.

As far as your contention that a transformer isolated supply is only
safe
with double insulated equipment, that simply isn't true. The only way
that
you can drive current through the body from such an isolation
transformer,
is to hang yourself across both output terminals. Either terminal to
ground
will present no electric shock hazard at all.

Arfa

Sounds too good to be true.

Well, if you understood the principles of isolation transformers, which
as
well as being used on building sites for obvious reasons, are also to
be
found in every professional electronics workshop, to render safe, the
need
to work on live equipment employing such potentially lethal nasties, as
switch mode power supplies, then you would know that it isn't too good
to
be
true - it simply *is* true. Sketch it down on a piece of paper then
have
a
good think about it.

Arfa

The only 'isolation transformers' I've come across, are earthed - and
either have an output restricted to 50V or less (that threshold at which
the human body's resistance drops substantially) or provide a good earth
connection for the appliance. An isolation transformer /does/
disconnect
the connection that exists between the power station and the ground and
is
carried by the 'live' or 'hot' cable, but that is /not/ the same as the
safety 'earth' connection which is meant to provide a relatively safe
return path in case exposed metal parts of the appliance accidentally
become connected to the power supply.


Neutral and ground are bonded together at the substation



The 'earth' connection provided by an 'isolation transformer' to the
appliances running off it, may be arranged to effectively create a
'short-circuit' on the output windings of the transformer if any current
flows through it, and that should trigger the safety cut-off (probably a
'residual current device'). Or the 'earth' connection will pass
straight
through to the same 'earth' as the mains supply provides.

A double-insulated appliance has no exposed metal parts that can become
connected to the power supply, and that's why they are permitted to be
used with no 'earth'.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~

Hmmmm. Your understanding of the principles of ground isolation by use of
a
transformer seem very flawed I'm afraid, as also is your knowledge of
electricity distribution schemes, and earth / neutral commonality.

Arfa


Whiskers is an idiot from the 24hoursupport.helpdesk newsgroup.
Probably got trolled here by the Hucker idiot.

PHucker usually hangs out on alt.binaries.chatter , I can't recall seeing
whiskers there. PHucker sometimes trolls on the sci.electronics groups -
usually asking stupid questions then criticizing the answers he's given.

Lol yeah that pretty much sums it up. I think he's actually smart
enough to engage in some useful conversations should he choose to do
so.

 

[ian field]

"Meat Plow" <meat@petitmorte.net> wrote in message
news:2bcalk.4i2.17.4@news.alt.net...

On Wed, 12 Nov 2008 21:23:05 -0000, "ian field"
gangprobing.alien@ntlworld.com>wrote:


"Meat Plow" <meat@petitmorte.net> wrote in message
news:2bc3rq.btk.19.1@news.alt.net...
On Wed, 12 Nov 2008 14:50:28 -0000, "Arfa Daily"
arfa.daily@ntlworld.com>wrote:


"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghlo20.bmt.catwheezel@ID-107770.user.individual.net...
On 2008-11-12, Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghjjbg.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-11, Arfa Daily <arfa.daily@ntlworld.com> wrote:
"Whiskers" <catwheezel@operamail.com> wrote in message
news:slrnghja8j.e5j.catwheezel@ID-107770.user.individual.net...
On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:
In article
slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

[...]

A system carrying a lot of amps to the load that's drawing it, is
no
more
or
less dangerous than one that's only carrying a small current,
except
in
as
much as there is a greater potential for heat failure at connection
points
within that system. A high voltage system, irrespective of how many
amps
it
is capable of carrying above a few milliamps, is far more dangerous
to
a
human, than a low voltage system good for a few hundred amps. Given
the
(reasonably) constant resistance of any described path through the
human
body, a voltage of a hundred volts with a current availability of
as
little
as 50mA, may be enough to kill under the right (wrong!)
circumstances.

So a charge of 10kV from walking across a carpet (DC) , or a
"non-lethal"
50kV "Tazer" (AC), are more dangerous than a 1kV power line? The
danger
from 'High Voltage' power lines comes from the vast amount of
current
they
can deliver.

You see, there you go getting your apples and oranges mixed up again.
A
static charge from a carpet is not lethal to you because it is an
extremely
high resistance source. That is the nature of a static charge. No
matter
whether it is 1kV, 10kV or 40kV, the source resistance will ensure
that
only
uA will flow for decimals of a uS. Enough to give you a nasty little
crack,
yes, but not enough to come within several orders of magnitude of
being
lethal. The same applies to the taser. It is designed to not be able
to
supply enough current (theoretically) to be lethal. However, its aim
is
to
incapacitate by disrupting nerve activity and causing extreme pain.
To
do
this, the charge is applied to the receiving body in multiple
short-duration
pulses. In some cases, this has proven to be fatal, I believe, due to
the
length of time that the pulses are delivered for. On the other hand,
a
high
voltage power line, or even a fairly low voltage household supply,
*is*
potentially lethal not because it can deliver huge amounts of amps,
but
because the voltage that is present, is sufficient to drive *enough*
(mili)
amps from that low resistance source through the conduction path
within
the
body.

Precisely; it isn't the voltage that's lethal, it's the current. If
the
current isn't available, the voltage is pretty harmless. High-voltage
mains power lines carry a /lot/ of current, whereas high-voltage
'Tazers'
don't.

On
the other hand, a low voltage welding supply, will not have enough
voltage
behind it to push enough current through that same path to kill
you,
even
though that supply is good for 200 amps or more.

What voltage does a 'low voltage' welder operate at? Don't they use
capacitors to raise the supply voltage to at least 40kV? Or can
welding
really happen at 12V?

Yes, arc welding can occur at 12v and, in fact, at lower voltages
than
this,
although there are many different methods these days of generating
and
controlling the welding arc, though none that operate by charging
caps
to
the sorts of voltages that you are talking about, as far as I am
aware.
In
general, arc welding is a high current rather than high voltage
system.
Spot
welders sometimes work by charging very large capacitors to low
voltages.
The reason that the low voltage arc welder is not capable of killing
you,
any more than a car battery can, is because although both are
extremely
low
internal resistance sources, and hence capable of supplying large
amounts
of
current to a low resistance load, the human body is a much higher
resistance
load, so the 12v is not capable of pushing enough miliamps through
that
path, to cause electrocution - or even electric shock.

OK, I'm not familiar with arc welding, and I'm surprised that 12V is
enough to strike an arc. But your comment that it is the high current
that matters for creating a weld, rather supports my contention that
current is more dangerous than voltage.

Electron beam welding (which you probaby won't find happening in a
garden
shed or on a building site) requires many thousand volts, but only a
small
current (less than 1A).

The only welding I've ever done myself, involved a coke-burning forge
and
a heavy hammer.

As far as your contention that a transformer isolated supply is
only
safe
with double insulated equipment, that simply isn't true. The only
way
that
you can drive current through the body from such an isolation
transformer,
is to hang yourself across both output terminals. Either terminal
to
ground
will present no electric shock hazard at all.

Arfa

Sounds too good to be true.

Well, if you understood the principles of isolation transformers,
which
as
well as being used on building sites for obvious reasons, are also to
be
found in every professional electronics workshop, to render safe, the
need
to work on live equipment employing such potentially lethal nasties,
as
switch mode power supplies, then you would know that it isn't too
good
to
be
true - it simply *is* true. Sketch it down on a piece of paper then
have
a
good think about it.

Arfa

The only 'isolation transformers' I've come across, are earthed - and
either have an output restricted to 50V or less (that threshold at
which
the human body's resistance drops substantially) or provide a good
earth
connection for the appliance. An isolation transformer /does/
disconnect
the connection that exists between the power station and the ground
and
is
carried by the 'live' or 'hot' cable, but that is /not/ the same as
the
safety 'earth' connection which is meant to provide a relatively safe
return path in case exposed metal parts of the appliance accidentally
become connected to the power supply.


Neutral and ground are bonded together at the substation



The 'earth' connection provided by an 'isolation transformer' to the
appliances running off it, may be arranged to effectively create a
'short-circuit' on the output windings of the transformer if any
current
flows through it, and that should trigger the safety cut-off (probably
a
'residual current device'). Or the 'earth' connection will pass
straight
through to the same 'earth' as the mains supply provides.

A double-insulated appliance has no exposed metal parts that can
become
connected to the power supply, and that's why they are permitted to be
used with no 'earth'.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~

Hmmmm. Your understanding of the principles of ground isolation by use
of
a
transformer seem very flawed I'm afraid, as also is your knowledge of
electricity distribution schemes, and earth / neutral commonality.

Arfa


Whiskers is an idiot from the 24hoursupport.helpdesk newsgroup.
Probably got trolled here by the Hucker idiot.

PHucker usually hangs out on alt.binaries.chatter , I can't recall seeing
whiskers there. PHucker sometimes trolls on the sci.electronics groups -
usually asking stupid questions then criticizing the answers he's given.


Lol yeah that pretty much sums it up. I think he's actually smart
enough to engage in some useful conversations should he choose to do
so.

He claims to have a degree in physics, yet according to him he found physics
too boring so he settled for a tech support job in a computer dept - funny
how he visits this group yet never seems to contribute in any meaningful
way.

 

[David Nebenzahl]

On 11/11/2008 7:47 AM Whiskers spake thus:

On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:

In article <slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

Our power sockets are only 3kW each - but it isn't the Watts that really
hurt, or even the Volts; it's the Amps you really need to be careful
with. 60 Amps at a Japanese 100V would be a lot more dangerous than 30
Amps at a European 230V. (Although either could kill you, so the
difference could be academic as far as the one grasping the wires is
concerned).

Not quite sure what you mean. The current drawn by a given resistance is
proportional to the voltage - and touching a 1000 amp supply is no more
dangerous to a human than touching a 1 amp one.

Well you go right ahead and play with the 1000 Amp wires if you want to,
but wait for me to get out of sight and earshot first - I'm a bit
squeamish.

He (Dave P.) is right. Once you're about the amount of current
sufficient to be lethal (which is measured in milliamps, not amperes),
the ampacity of a circuit you're touching--whether 15, 20 or 200
amps--matters not.

No reason to be overly impressed by a 60-amp circuit. No more deadly
than a 1-amp circuit.


--
I am a Canadian who was born and raised in The Netherlands. I live on
Planet Earth on a spot of land called Canada. We have noisy neighbours.

- harvested from Usenet

 

[VanguardLH]

David Nebenzahl replies to 13-month old thread:

He (Dave P.) is right. Once you're about the amount of current
sufficient to be lethal (which is measured in milliamps, not amperes),
the ampacity of a circuit you're touching--whether 15, 20 or 200
amps--matters not.

No reason to be overly impressed by a 60-amp circuit. No more deadly
than a 1-amp circuit.

Google Groups copy of old thread: http://preview.tinyurl.com/ylf7uo8

You thought any participant in that *OVER 1-YEAR OLD* thread was still
waiting for a response?

 

[David Nebenzahl]

On 12/30/2009 9:42 PM VanguardLH spake thus:

David Nebenzahl replies to 13-month old thread:

He (Dave P.) is right. Once you're about the amount of current
sufficient to be lethal (which is measured in milliamps, not amperes),
the ampacity of a circuit you're touching--whether 15, 20 or 200
amps--matters not.

No reason to be overly impressed by a 60-amp circuit. No more deadly
than a 1-amp circuit.

Google Groups copy of old thread: http://preview.tinyurl.com/ylf7uo8

You thought any participant in that *OVER 1-YEAR OLD* thread was still
waiting for a response?

You were reading an *OVER 1-YEAR-OLD* thread? and commenting on it? (And
look--I *did* get a response!)

In my defense, I neglected to look at the year; thought it was about a
month old.


--
I am a Canadian who was born and raised in The Netherlands. I live on
Planet Earth on a spot of land called Canada. We have noisy neighbours.

- harvested from Usenet

 

[nobody >]

David Nebenzahl wrote:

On 11/11/2008 7:47 AM Whiskers spake thus:

On 2008-11-10, Dave Plowman (News) <dave@davenoise.co.uk> wrote:

In article <slrnghhb1o.bes.catwheezel@ID-107770.user.individual.net>,
Whiskers <catwheezel@operamail.com> wrote:

Our power sockets are only 3kW each - but it isn't the Watts that
really
hurt, or even the Volts; it's the Amps you really need to be careful
with. 60 Amps at a Japanese 100V would be a lot more dangerous than 30
Amps at a European 230V. (Although either could kill you, so the
difference could be academic as far as the one grasping the wires is
concerned).

Not quite sure what you mean. The current drawn by a given resistance is
proportional to the voltage - and touching a 1000 amp supply is no more
dangerous to a human than touching a 1 amp one.

Well you go right ahead and play with the 1000 Amp wires if you want to,
but wait for me to get out of sight and earshot first - I'm a bit
squeamish.

He (Dave P.) is right. Once you're about the amount of current
sufficient to be lethal (which is measured in milliamps, not amperes),
the ampacity of a circuit you're touching--whether 15, 20 or 200
amps--matters not.

No reason to be overly impressed by a 60-amp circuit. No more deadly
than a 1-amp circuit.

That's true if you are just worried about contact shock hazard.

Arc flash/blast is a whole 'nother ball game.

http://www.easypower.com/arc_flash/arc_flash_videos.php

http://205.243.100.155/frames/mpg/480VArcFlash1.wmv

http://205.243.100.155/frames/longarc.htm