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AC switch fault current philosophy
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Piglet
Dec 28, 2017, 7:29:16 AM12/28/17
to
When designing a semiconductor based switch for AC mains power which is
the better philosophy to handling a load side short circuit:
1. Use devices rugged enough to pass the fault current and allow the
upstream breaker or fuse to operate as usual if the switch had been
mechanical;
2. Switch off fast enough to break the current before damage occurs and
retry a second or two later?
piglet
the better philosophy to handling a load side short circuit:
1. Use devices rugged enough to pass the fault current and allow the
upstream breaker or fuse to operate as usual if the switch had been
mechanical;
2. Switch off fast enough to break the current before damage occurs and
retry a second or two later?
piglet
Phil Allison
Dec 28, 2017, 7:47:37 AM12/28/17
to
piglet squeeled :
-----------------
** The proven way is to do both.
1. Use a very rugged AC switch device, like a 40A triac or 60A SCR pair with the largest half cycle surge rating - like 500 to 1000A.
2. Install a fast acting magnetic breaker able to break the turn off arc in one or two milliseconds.
If there are other good ways, designers of pro-lighting dimmer don't know about them.
BTW:
Stop posting fuckwit questions about stuff you are clueless about.
..... Phil
-----------------
1. Use a very rugged AC switch device, like a 40A triac or 60A SCR pair with the largest half cycle surge rating - like 500 to 1000A.
2. Install a fast acting magnetic breaker able to break the turn off arc in one or two milliseconds.
If there are other good ways, designers of pro-lighting dimmer don't know about them.
BTW:
Stop posting fuckwit questions about stuff you are clueless about.
..... Phil
Tim Williams
Dec 28, 2017, 10:04:06 AM12/28/17
to
If you're talking thyristors (SCR/TRIAC), you have no choice but to do 1.
Fault current ramps up well within a cycle, so there's no chance to turn it
off later. Make sure you use a fuse with a smaller I^2t rating than the
thyristor.
For industrial applications, there are "semiconductor fuses": super fast,
they clear in less than a cycle. For smaller (consumer scale) loads, a
regular fast-blow may have low enough I^2t, or alternately, you can afford
to use a somewhat larger thyristor.
Otherwise, with transistors, #1 is impossible. No transistor can burn a
mains fuse without itself blowing far, far sooner. Current must be switched
off, diverted to a snubber network (usually an RCD clamp, TVS or MOV), and
then either it stays off, or it turns back on and off, controlling current
(with an inductor added, to set a maximum dI/dt).
In a switching-current-limit mode of operation, fault time is limited by the
energy capacity of the clamping device. If you can "stir" the energy back
into the source (easier with a DC circuit -- i.e., a regular buck
converter), you can run a limit condition basically forever (or at least,
until something else overheats). If not, then the dissipating device will
eventually overheat, and you'll need to monitor that and stop at some point.
Tim
--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: https://www.seventransistorlabs.com/
"Piglet" <erichp...@hotmail.com> wrote in message
news:p22o2k$svd$1...@dont-email.me...
Fault current ramps up well within a cycle, so there's no chance to turn it
off later. Make sure you use a fuse with a smaller I^2t rating than the
thyristor.
For industrial applications, there are "semiconductor fuses": super fast,
they clear in less than a cycle. For smaller (consumer scale) loads, a
regular fast-blow may have low enough I^2t, or alternately, you can afford
to use a somewhat larger thyristor.
Otherwise, with transistors, #1 is impossible. No transistor can burn a
mains fuse without itself blowing far, far sooner. Current must be switched
off, diverted to a snubber network (usually an RCD clamp, TVS or MOV), and
then either it stays off, or it turns back on and off, controlling current
(with an inductor added, to set a maximum dI/dt).
In a switching-current-limit mode of operation, fault time is limited by the
energy capacity of the clamping device. If you can "stir" the energy back
into the source (easier with a DC circuit -- i.e., a regular buck
converter), you can run a limit condition basically forever (or at least,
until something else overheats). If not, then the dissipating device will
eventually overheat, and you'll need to monitor that and stop at some point.
Tim
--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: https://www.seventransistorlabs.com/
"Piglet" <erichp...@hotmail.com> wrote in message
news:p22o2k$svd$1...@dont-email.me...
Piglet
Dec 28, 2017, 11:53:10 AM12/28/17
to
> This email has been checked for viruses by AVG.
> http://www.avg.com
>
Thanks Phil. Happy New Year
piglet
Piglet
Dec 28, 2017, 12:00:29 PM12/28/17
to
On 28/12/2017 15:03, Tim Williams wrote:
> If you're talking thyristors (SCR/TRIAC), you have no choice but to do
> 1. Fault current ramps up well within a cycle, so there's no chance to
> turn it off later. Make sure you use a fuse with a smaller I^2t rating
> than the thyristor.
>
> For industrial applications, there are "semiconductor fuses": super
> fast, they clear in less than a cycle. For smaller (consumer scale)
> loads, a regular fast-blow may have low enough I^2t, or alternately, you
> can afford to use a somewhat larger thyristor.
>
> Otherwise, with transistors, #1 is impossible. No transistor can burn a
> mains fuse without itself blowing far, far sooner. Current must be
> switched off, diverted to a snubber network (usually an RCD clamp, TVS
> or MOV), and then either it stays off, or it turns back on and off,
> controlling current (with an inductor added, to set a maximum dI/dt).
>
> In a switching-current-limit mode of operation, fault time is limited by
> the energy capacity of the clamping device. If you can "stir" the
> energy back into the source (easier with a DC circuit -- i.e., a regular
> buck converter), you can run a limit condition basically forever (or at
> least, until something else overheats). If not, then the dissipating
> device will eventually overheat, and you'll need to monitor that and
> stop at some point.
>
> Tim
>
Thanks Tim. My preferred option was always a big enough SCR but I asked
> If you're talking thyristors (SCR/TRIAC), you have no choice but to do
> 1. Fault current ramps up well within a cycle, so there's no chance to
> turn it off later. Make sure you use a fuse with a smaller I^2t rating
> than the thyristor.
>
> For industrial applications, there are "semiconductor fuses": super
> fast, they clear in less than a cycle. For smaller (consumer scale)
> loads, a regular fast-blow may have low enough I^2t, or alternately, you
> can afford to use a somewhat larger thyristor.
>
> Otherwise, with transistors, #1 is impossible. No transistor can burn a
> mains fuse without itself blowing far, far sooner. Current must be
> switched off, diverted to a snubber network (usually an RCD clamp, TVS
> or MOV), and then either it stays off, or it turns back on and off,
> controlling current (with an inductor added, to set a maximum dI/dt).
>
> In a switching-current-limit mode of operation, fault time is limited by
> the energy capacity of the clamping device. If you can "stir" the
> energy back into the source (easier with a DC circuit -- i.e., a regular
> buck converter), you can run a limit condition basically forever (or at
> least, until something else overheats). If not, then the dissipating
> device will eventually overheat, and you'll need to monitor that and
> stop at some point.
>
> Tim
>
in case that option is considered too old fashioned now that MOSFETs are
becoming available that with only a small amount of inductance and
snubbing can switch off fast enough to survive.
SCR I2t is still much much cheaper than equivalent MOSFET SOA :)
piglet
Don Kuenz
Dec 28, 2017, 1:46:01 PM12/28/17
to
short. That way you simultaneously protect the shorted device and send
users a dramatic message that something's wrong.
Thank you,
--
Don Kuenz, KB7RPU
Piotr Wyderski
Dec 28, 2017, 2:21:49 PM12/28/17
to
Piglet wrote:
> SCR I2t is still much much cheaper than equivalent MOSFET SOA :)
Is it? I mean, can you buy the latter at all? Even IGBTs have
> SCR I2t is still much much cheaper than equivalent MOSFET SOA :)
short-circuit ratings measured in microseconds, with the values
of 10us and 5us occuring most often.
Best regards, Piotr
Jim Thompson
Dec 28, 2017, 2:48:30 PM12/28/17
to
On Thu, 28 Dec 2017 12:29:07 +0000, Piglet <erichp...@hotmail.com>
wrote:
A round-about way that I have found very useful: Sense current, blow
fuse with "crowbar" circuit... amazing how much light a fast-blow fuse
will make ;-)
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
It's what you learn, after you know it all, that counts.
wrote:
fuse with "crowbar" circuit... amazing how much light a fast-blow fuse
will make ;-)
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
It's what you learn, after you know it all, that counts.
Lasse Langwadt Christensen
Dec 28, 2017, 2:57:09 PM12/28/17
to
Tim Williams
Dec 28, 2017, 3:16:50 PM12/28/17
to
"Don Kuenz" <g...@crcomp.net> wrote in message news:2017...@crcomp.net...
If you have a shunt coil to trip the breaker separately (like a lot of
UL1077 breakers do, or the guts of a GFCI receptacle), you can open the
circuit without drawing fault current. Though that still won't act fast
enough to save a transistor (not without a switching mechanism like I
described, anyway).
> You might limit the current and trip the mains breaker to cope with the
> short. That way you simultaneously protect the shorted device and send
> users a dramatic message that something's wrong.
How does that work?
> short. That way you simultaneously protect the shorted device and send
> users a dramatic message that something's wrong.
If you have a shunt coil to trip the breaker separately (like a lot of
UL1077 breakers do, or the guts of a GFCI receptacle), you can open the
circuit without drawing fault current. Though that still won't act fast
enough to save a transistor (not without a switching mechanism like I
described, anyway).
pcdh...@gmail.com
Dec 28, 2017, 3:27:43 PM12/28/17
to
>You might limit the current and trip the mains breaker to cope with the
>short. That way you simultaneously protect the shorted device and send
>users a dramatic message that something's wrong.
You mean the breaker at the _panel_? How do you know if it's magnetic or thermal?
>short. That way you simultaneously protect the shorted device and send
>users a dramatic message that something's wrong.
And then somebody plugs it into daisy-chained extension cords and your 'safety device' burns down the building. Brilliant all round. :(
Cheers
Phil Hobbs
George Herold
Dec 28, 2017, 4:16:20 PM12/28/17
to
I don't see any reason for you to start off so rude...
get a grip.
George H.
>
>
> ..... Phil
tabb...@gmail.com
Dec 28, 2017, 4:16:49 PM12/28/17
to
NT
George Herold
Dec 28, 2017, 4:28:45 PM12/28/17
to
a rugged switch.
George H.
pcdh...@gmail.com
Dec 28, 2017, 5:43:05 PM12/28/17
to
>On Thursday, 28 December 2017 20:27:43 UTC, pcdh...@gmail.com wrote:
>> >You might limit the current and trip the mains breaker to cope with the
>> >short. That way you simultaneously protect the shorted device and send
>> >users a dramatic message that something's wrong.
>
>> You mean the breaker at the _panel_? How do you know if it's magnetic or thermal?
>>
>> And then somebody plugs it into daisy-chained extension cords and your 'safety
>> device' burns down the building. Brilliant all round. :(
>> >You might limit the current and trip the mains breaker to cope with the
>> >short. That way you simultaneously protect the shorted device and send
>> >users a dramatic message that something's wrong.
>
>> You mean the breaker at the _panel_? How do you know if it's magnetic or thermal?
>>
>> And then somebody plugs it into daisy-chained extension cords and your 'safety
>> device' burns down the building. Brilliant all round. :(
>don't implement it stupidly. The current limiter must have overheat protection.
How are you going to do that if you don't know how it's connected?
Building a known fast breaker into the box, I get. Relying on the capabilities of a hypothetical breaker at an unknown upstream point, not so much.
Cheers
Phil Hobbs
tabb...@gmail.com
Dec 28, 2017, 6:25:22 PM12/28/17
to
On Thursday, 28 December 2017 22:43:05 UTC, pcdh...@gmail.com wrote:
>NT:
> Building a known fast breaker into the box, I get. Relying on the capabilities of a hypothetical breaker at an unknown upstream point, not so much.
>
> Cheers
>
> Phil Hobbs
Mains supply breakers aren't hypothetical. In UK they're well defined. I presume they are in all other 1st world countries too.
And the whole point of overheat cutout is that it interrupts the current if for any reason the supply fails to. That could be as simple as a fusible resistor.
NT
>NT:
> >On Thursday, 28 December 2017 20:27:43 UTC, pcdh...@gmail.com wrote:
> >> >You might limit the current and trip the mains breaker to cope with the
> >> >short. That way you simultaneously protect the shorted device and send
> >> >users a dramatic message that something's wrong.
> >
> >> You mean the breaker at the _panel_? How do you know if it's magnetic or thermal?
> >>
> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
> >> device' burns down the building. Brilliant all round. :(
>
> >don't implement it stupidly. The current limiter must have overheat protection.
>
> How are you going to do that if you don't know how it's connected?
I'm not making sense of that question
> >> >You might limit the current and trip the mains breaker to cope with the
> >> >short. That way you simultaneously protect the shorted device and send
> >> >users a dramatic message that something's wrong.
> >
> >> You mean the breaker at the _panel_? How do you know if it's magnetic or thermal?
> >>
> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
> >> device' burns down the building. Brilliant all round. :(
>
> >don't implement it stupidly. The current limiter must have overheat protection.
>
> How are you going to do that if you don't know how it's connected?
> Building a known fast breaker into the box, I get. Relying on the capabilities of a hypothetical breaker at an unknown upstream point, not so much.
>
> Cheers
>
> Phil Hobbs
And the whole point of overheat cutout is that it interrupts the current if for any reason the supply fails to. That could be as simple as a fusible resistor.
NT
Phil Allison
Dec 28, 2017, 7:51:54 PM12/28/17
to
George Herold wrote:
-------------------------
> I don't see any reason for you to start off so rude...
** Clearly, I started off quite formally.
Then I gave him a smack for posting yet another TROLL.
Trolls are questions that HAVE no answer because the problem is undefined.
.... Phil
-------------------------
>
> > >
> > >
> > > When designing a semiconductor based switch for AC mains power which is
> > > the better philosophy to handling a load side short circuit:
> > >
> > > 1. Use devices rugged enough to pass the fault current and allow the
> > > upstream breaker or fuse to operate as usual if the switch had been
> > > mechanical;
> > >
> > > 2. Switch off fast enough to break the current before damage occurs and
> > > retry a second or two later?
> > >
> > >
> >
> > ** The proven way is to do both.
> >
> > 1. Use a very rugged AC switch device, like a 40A triac or 60A SCR pair with the largest half cycle surge rating - like 500 to 1000A.
> >
> > 2. Install a fast acting magnetic breaker able to break the turn off arc in one or two milliseconds.
> >
> > If there are other good ways, designers of pro-lighting dimmer don't know about them.
> >
> > BTW:
> >
> > Stop posting fuckwit questions about stuff you are clueless about.
>>
>
> Phil, WTF? I was thrilled to see a question from piglet.
>
** You need help.
> > >
> > >
> > > When designing a semiconductor based switch for AC mains power which is
> > > the better philosophy to handling a load side short circuit:
> > >
> > > 1. Use devices rugged enough to pass the fault current and allow the
> > > upstream breaker or fuse to operate as usual if the switch had been
> > > mechanical;
> > >
> > > 2. Switch off fast enough to break the current before damage occurs and
> > > retry a second or two later?
> > >
> > >
> >
> > ** The proven way is to do both.
> >
> > 1. Use a very rugged AC switch device, like a 40A triac or 60A SCR pair with the largest half cycle surge rating - like 500 to 1000A.
> >
> > 2. Install a fast acting magnetic breaker able to break the turn off arc in one or two milliseconds.
> >
> > If there are other good ways, designers of pro-lighting dimmer don't know about them.
> >
> > BTW:
> >
> > Stop posting fuckwit questions about stuff you are clueless about.
>>
>
> Phil, WTF? I was thrilled to see a question from piglet.
>
> I don't see any reason for you to start off so rude...
Then I gave him a smack for posting yet another TROLL.
Trolls are questions that HAVE no answer because the problem is undefined.
.... Phil
pcdh...@gmail.com
Dec 28, 2017, 10:04:44 PM12/28/17
to
>> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
>> >> device' burns down the building. Brilliant all round. :(
>>
>> >don't implement it stupidly. The current limiter must have overheat protection.
>>
>> How are you going to do that if you don't know how it's connected?
>I'm not making sense of that question
So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
>> >> device' burns down the building. Brilliant all round. :(
>>
>> >don't implement it stupidly. The current limiter must have overheat protection.
>>
>> How are you going to do that if you don't know how it's connected?
>I'm not making sense of that question
> Building a known fast breaker into the box, I get. Relying on the capabilities of a hypothetical breaker at an unknown upstream point, not so much.
>Mains supply breakers aren't hypothetical. In UK they're well defined.
>I presume they are in all other 1st world countries too.
There are magnetic (fast) and thermal (slow) types here. A thermal breaker might very well not clear the short before the thyristor melted. Or the wiring might be marginal, but good enough for many more years unless somebody did something idiotic like shorting the mains.
>I presume they are in all other 1st world countries too.
In any case, round these parts if you caused a fire by deliberately shorting the mains to ground, you'd get sued right down to your socks, and rightly so. If you did it in France or Italy and someone died as a result, you might very well go to jail.
>And the whole point of overheat cutout is that it interrupts
>the current if for any reason the supply fails to. That could be
>as simple as a fusible resistor.
I wouldn't want to be liable for a claim that large, personally.
Cheers
Phil Hobbs
Piglet
Dec 29, 2017, 7:45:16 AM12/29/17
to
On 28/12/2017 19:57, Lasse Langwadt Christensen wrote:
> Den torsdag den 28. december 2017 kl. 18.00.29 UTC+1 skrev piglet:
>
> but you can turn of a fet in microseconds
>
Exactly. Fast turn off makes possible something not possible before.
> Den torsdag den 28. december 2017 kl. 18.00.29 UTC+1 skrev piglet:
>
> but you can turn of a fet in microseconds
>
So which is better, a few milli-seconds of hundreds of amperes and which
causes a clearly identifiable indication of fault requiring manual
intervention to reset - or - a few tens of micro-seconds of tens of
amperes and a circuit that automatically resumes when the fault is cleared?
Also faults can range from a transient tungsten filament fragment
falling across supports to the non-transient nail through a cable.
For example if this were a domestic light switch which mode would be
preferable? Should I stick with the tried and tested method or is there
any point in exploring the newer mode?
Don't mean to be a troll but I do appreciate your help settling this
question.
piglet
Winfield Hill
Dec 29, 2017, 8:13:51 AM12/29/17
to
Piglet wrote...
are better made with IGBTs than MOSFETs, because the IGBT's
Vce(sat) is considerably-less than the FET's Id*Rds(on).
--
Thanks,
- Win
>
> Exactly. Fast turn off makes possible something not possible before.
Let's be clear here: High-current AC-line-voltage switches
> Exactly. Fast turn off makes possible something not possible before.
are better made with IGBTs than MOSFETs, because the IGBT's
Vce(sat) is considerably-less than the FET's Id*Rds(on).
--
Thanks,
- Win
Don Kuenz
Dec 29, 2017, 9:19:21 AM12/29/17
to
switch only makes sense to me when its part of the electrical wiring
and not plugged into either an outlet or a daisy chain of extension
cords. (BTW, isn't a daisy chain of extension cords against the regs?)
tabb...@gmail.com
Dec 29, 2017, 9:20:34 AM12/29/17
to
On Friday, 29 December 2017 03:04:44 UTC, pcdh...@gmail.com wrote:
> >> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
> >> >> device' burns down the building. Brilliant all round. :(
> >>
> >> >don't implement it stupidly. The current limiter must have overheat protection.
> >>
> >> How are you going to do that if you don't know how it's connected?
>
> >I'm not making sense of that question
>
> So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
Added resistance in daisy chained extensions does not get what I described into trouble.
> >> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
> >> >> device' burns down the building. Brilliant all round. :(
> >>
> >> >don't implement it stupidly. The current limiter must have overheat protection.
> >>
> >> How are you going to do that if you don't know how it's connected?
>
> >I'm not making sense of that question
>
> So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
> > Building a known fast breaker into the box, I get. Relying on the capabilities of a hypothetical breaker at an unknown upstream point, not so much.
>
>
> >Mains supply breakers aren't hypothetical. In UK they're well defined.
> >I presume they are in all other 1st world countries too.
>
> There are magnetic (fast) and thermal (slow) types here. A thermal breaker might very well not clear the short before the thyristor melted.
> Or the wiring might be marginal, but good enough for many more years unless somebody did something idiotic like shorting the mains.
> In any case, round these parts if you caused a fire by deliberately shorting the mains to ground, you'd get sued right down to your socks, and rightly so. If you did it in France or Italy and someone died as a result, you might very well go to jail.
> >And the whole point of overheat cutout is that it interrupts
> >the current if for any reason the supply fails to. That could be
> >as simple as a fusible resistor.
>
> "For any reason?"
>
> I wouldn't want to be liable for a claim that large, personally.
>
> Cheers
>
> Phil Hobbs
NT
glen walpert
Dec 29, 2017, 11:03:46 AM12/29/17
to
On Thu, 28 Dec 2017 12:27:34 -0800, pcdhobbs wrote:
>>You might limit the current and trip the mains breaker to cope with the
>>short. That way you simultaneously protect the shorted device and send
>>users a dramatic message that something's wrong.
>
> You mean the breaker at the _panel_? How do you know if it's magnetic or
> thermal?
The tripping characteristics of circuit breakers listed for use in US low
>>You might limit the current and trip the mains breaker to cope with the
>>short. That way you simultaneously protect the shorted device and send
>>users a dramatic message that something's wrong.
>
> You mean the breaker at the _panel_? How do you know if it's magnetic or
> thermal?
voltage power distribution systems is well defined. A quick search on
"Circuit Breaker Characteristic Trip Curves and Coordination" found:
https://www.schneider-electric.us/en/download/document/0600DB0105/
and much more, which I did not pursue.
Power distribution system reliability philosophy requires interrupting
faults as close to the source as possible, in order to minimize impact to
other loads. For example, the power distribution to a hospital OR might
be fully coordinated against a single fault; designed so that when the
distribution system is fully loaded no single fault (overload or short
circuit) can trip any but the closest breaker. Other systems may be
partially coordinated or coordinated against multiple faults.
Applying this basic philosophy to plug connected loads, they should never
be able to trip the main panel breaker except in the case of a cord fault.
I haven't done any coordinated power dist work in this century, but IIRC
all low voltage (600 volts or less) molded case circuit breakers rated
for 600 Amps or less which are listed for use in the US are guaranteed
not to trip at less than 80% of current rating continuous duty,
guaranteed to trip within two cycles for short circuit up to rated Amps
Interrupting Current (10kA for almost all 120/240) but not guaranteed to
remain usable after clearing a short circuit (must fail open).
If doing a coordination study one uses trip curves for the exact breakers
used, but for general consideration of breaker performance they are all
very similar and the Schneider curves are representative.
> And then somebody plugs it into daisy-chained extension cords and your
> 'safety device' burns down the building. Brilliant all round. :(
Glen
George Herold
Dec 29, 2017, 6:48:47 PM12/29/17
to
On Thursday, December 28, 2017 at 10:04:44 PM UTC-5, pcdh...@gmail.com wrote:
> >> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
> >> >> device' burns down the building. Brilliant all round. :(
> >>
> >> >don't implement it stupidly. The current limiter must have overheat protection.
> >>
> >> How are you going to do that if you don't know how it's connected?
>
> >I'm not making sense of that question
>
> So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
Phil, (or someone) can you explain about the daisy chained power strips.
> >> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
> >> >> device' burns down the building. Brilliant all round. :(
> >>
> >> >don't implement it stupidly. The current limiter must have overheat protection.
> >>
> >> How are you going to do that if you don't know how it's connected?
>
> >I'm not making sense of that question
>
> So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
We got yelled at, at a trade show, but never quite understood the explanation.
There's a short in something on the end of the chain...
Then.?
Thanks,
George H.
k...@notreal.com
Dec 29, 2017, 6:59:58 PM12/29/17
to
On Fri, 29 Dec 2017 15:48:42 -0800 (PST), George Herold
<ghe...@teachspin.com> wrote:
>On Thursday, December 28, 2017 at 10:04:44 PM UTC-5, pcdh...@gmail.com wrote:
>> >> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
>> >> >> device' burns down the building. Brilliant all round. :(
>> >>
>> >> >don't implement it stupidly. The current limiter must have overheat protection.
>> >>
>> >> How are you going to do that if you don't know how it's connected?
>>
>> >I'm not making sense of that question
>>
>> So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
>
>Phil, (or someone) can you explain about the daisy chained power strips.
>We got yelled at, at a trade show, but never quite understood the explanation.
>
>There's a short in something on the end of the chain...
>Then.?
There are a couple of issues. One is the multiple connections. The
<ghe...@teachspin.com> wrote:
>On Thursday, December 28, 2017 at 10:04:44 PM UTC-5, pcdh...@gmail.com wrote:
>> >> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
>> >> >> device' burns down the building. Brilliant all round. :(
>> >>
>> >> >don't implement it stupidly. The current limiter must have overheat protection.
>> >>
>> >> How are you going to do that if you don't know how it's connected?
>>
>> >I'm not making sense of that question
>>
>> So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
>
>Phil, (or someone) can you explain about the daisy chained power strips.
>We got yelled at, at a trade show, but never quite understood the explanation.
>
>There's a short in something on the end of the chain...
>Then.?
chances of a fire increase drastically, the more plugs inline.
Extension cords tend to be used often and the outlets tend to wear
(relax) causing high-resistance connections. Multiple in series isn't
a good idea. Another issue is the concept of using the right tool for
the job.
Phil Allison
Dec 29, 2017, 8:03:34 PM12/29/17
to
George Herold wrote:
----------------------
Multiple outlet strips sold here have overall 10Amp thermal breakers installed, to protect cabling and limit the chances of tripping a remote breaker.
The only safety issue I see is having too many safety ground links in series that ALL must work for the installation to be safe.
.... Phil
----------------------
>
>
> Phil, (or someone) can you explain about the daisy chained power strips.
> We got yelled at, at a trade show, but never quite understood the
> explanation.
>
>
** Likely because it was complete bullshit.
>
> Phil, (or someone) can you explain about the daisy chained power strips.
> We got yelled at, at a trade show, but never quite understood the
> explanation.
>
>
Multiple outlet strips sold here have overall 10Amp thermal breakers installed, to protect cabling and limit the chances of tripping a remote breaker.
The only safety issue I see is having too many safety ground links in series that ALL must work for the installation to be safe.
.... Phil
tabb...@gmail.com
Dec 29, 2017, 10:47:29 PM12/29/17
to
On Friday, 29 December 2017 23:48:47 UTC, George Herold wrote:
> On Thursday, December 28, 2017 at 10:04:44 PM UTC-5, pcdh...@gmail.com wrote:
> > >> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
> > >> >> device' burns down the building. Brilliant all round. :(
> > >>
> > >> >don't implement it stupidly. The current limiter must have overheat protection.
> > >>
> > >> How are you going to do that if you don't know how it's connected?
> >
> > >I'm not making sense of that question
> >
> > So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
>
> Phil, (or someone) can you explain about the daisy chained power strips.
> We got yelled at, at a trade show, but never quite understood the explanation.
>
> There's a short in something on the end of the chain...
> Then.?
>
> Thanks,
> George H.
In the UK daisy chained extension leads suffer from earth conductor resistance that rises above permitted spec, reducing short circuit to earth fault current, which has 3 effects.
> On Thursday, December 28, 2017 at 10:04:44 PM UTC-5, pcdh...@gmail.com wrote:
> > >> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
> > >> >> device' burns down the building. Brilliant all round. :(
> > >>
> > >> >don't implement it stupidly. The current limiter must have overheat protection.
> > >>
> > >> How are you going to do that if you don't know how it's connected?
> >
> > >I'm not making sense of that question
> >
> > So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
>
> Phil, (or someone) can you explain about the daisy chained power strips.
> We got yelled at, at a trade show, but never quite understood the explanation.
>
> There's a short in something on the end of the chain...
> Then.?
>
> Thanks,
> George H.
1. Earthed metalwork is then at a dangerous voltage until the fault is cleared
2. Fault clearance by the MCB is very slow
3. Fire may break out as a result - it's a lot of power to dissipate for too long.
However it has nothing whatever to do with what I was talking about, where the device in question
a) limits fault current to a safe value,
b) if the breaker supplying it does not clear it, then it clears itself by built in overheat or fuse protection
NT
Paul Hovnanian P.E.
Dec 29, 2017, 11:00:21 PM12/29/17
to
pcdh...@gmail.com wrote:
>
> You mean the breaker at the _panel_? How do you know if it's magnetic or
> thermal?
Edison base fuse with a penny.
>
> You mean the breaker at the _panel_? How do you know if it's magnetic or
> thermal?
Best bet is to incorporate your own fusible link into the device. Coordinate
with a 20 Amp breaker trip curve so that goes first. But if the upstream
device fails (or is bypassed), your device's internal fuse blows.
Your device is not repairable, but at leat you don't get sued for burning
down some moron's hose.
--
Paul Hovnanian mailto:Pa...@Hovnanian.com
------------------------------------------------------------------
If the first attempt at making a drawing board had been a failure,
what would they go back to?
Michael A Terrell
Dec 29, 2017, 11:49:55 PM12/29/17
to
Paul Hovnanian P.E. wrote:
> pcdh...@gmail.com wrote:
>>
>> You mean the breaker at the _panel_? How do you know if it's magnetic or
>> thermal?
>
> Edison base fuse with a penny.
>
> Best bet is to incorporate your own fusible link into the device.
> Coordinate with a 20 Amp breaker trip curve so that goes first. But
> if the upstream device fails (or is bypassed), your device's internal
> fuse blows.
>
> Your device is not repairable, but at leat you don't get sued for
> burning down some moron's hose.
Hose are cheap unless they are wearing them, when you set them on
> pcdh...@gmail.com wrote:
>>
>> You mean the breaker at the _panel_? How do you know if it's magnetic or
>> thermal?
>
> Edison base fuse with a penny.
>
> Best bet is to incorporate your own fusible link into the device.
> Coordinate with a 20 Amp breaker trip curve so that goes first. But
> if the upstream device fails (or is bypassed), your device's internal
> fuse blows.
>
> Your device is not repairable, but at leat you don't get sued for
> burning down some moron's hose.
fire. ;-)
upsid...@downunder.com
Dec 30, 2017, 4:42:33 AM12/30/17
to
>On Thursday, December 28, 2017 at 10:04:44 PM UTC-5, pcdh...@gmail.com wrote:
>> >> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
>> >> >> device' burns down the building. Brilliant all round. :(
>> >>
>> >> >don't implement it stupidly. The current limiter must have overheat protection.
>> >>
>> >> How are you going to do that if you don't know how it's connected?
>>
>> >I'm not making sense of that question
>>
>> So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
>
>Phil, (or someone) can you explain about the daisy chained power strips.
>We got yelled at, at a trade show, but never quite understood the explanation.
>
>There's a short in something on the end of the chain...
>Then.?
An ordinary fuse needs a short circuit current that is several times
>> >> >> And then somebody plugs it into daisy-chained extension cords and your 'safety
>> >> >> device' burns down the building. Brilliant all round. :(
>> >>
>> >> >don't implement it stupidly. The current limiter must have overheat protection.
>> >>
>> >> How are you going to do that if you don't know how it's connected?
>>
>> >I'm not making sense of that question
>>
>> So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
>
>Phil, (or someone) can you explain about the daisy chained power strips.
>We got yelled at, at a trade show, but never quite understood the explanation.
>
>There's a short in something on the end of the chain...
>Then.?
the fuse nominal current in order to blow in a few seconds. With only
twice the nominal current, it takes many minutes before the fuse
blows.
The short circuit current depends on the distribution transformer
secondary output voltage and the _total_ loop resistance. The worst
case loop resistance consist of the transformer to house, internal
wiring in the house to the mains socket, the extension cord(s)
resistance to the load connected to last extension cord. Multiply this
resistance by two, to include both the Live and Neutral wire. With a
short at the furthest point, this is the total loop resistance as seen
from the distribution transformer.
Assuming that a 5x nominal current will blow the fuse fast enough, in
230 V land with typically 10 A fuses, the _total_ loop resistance must
be less than 5 ohms.
In some countries it is assumed that there is a single maximum length
extension cord in the longest in-house wire to a socket for a specific
cross section (both in-house and extension cable). Plugging multiple
extension cords in series, especially with smaller cross section, will
increase the loop resistances too much.
As such, plugging multiple short (say 3 m) extension cords in series
with sufficient cross section is not a big problem.
One way to indirectly measure th total loop resistance is to plug an
incandescent lamp at the end of the last extension cord and then plug
in and out some big load and observe how the lamp flickers during the
transition. Incandescent lamps are very sensitive to small voltage
variations. A strong variation will indicate a relatively high loop
resistance.
Phil Allison
Dec 30, 2017, 5:01:13 AM12/30/17
to
upsid...@downunder.com wrote:
--------------------------------
George Herold
> >
> >Phil, (or someone) can you explain about the daisy chained power strips.
> >We got yelled at, at a trade show, but never quite understood the explanation.
> >
> >There's a short in something on the end of the chain...
> >Then.?
>
> An ordinary fuse needs a short circuit current that is several times
> the fuse nominal current in order to blow in a few seconds. With only
> twice the nominal current, it takes many minutes before the fuse
> blows.
>
> The short circuit current depends on the distribution transformer
> secondary output voltage and the _total_ loop resistance. The worst
> case loop resistance consist of the transformer to house, internal
> wiring in the house to the mains socket, the extension cord(s)
> resistance to the load connected to last extension cord. Multiply this
> resistance by two, to include both the Live and Neutral wire. With a
> short at the furthest point, this is the total loop resistance as seen
> from the distribution transformer.
>
> Assuming that a 5x nominal current will blow the fuse fast enough, in
> 230 V land with typically 10 A fuses, the _total_ loop resistance must
> be less than 5 ohms.
>
** FYI it takes over 100m of regular extension cable /cables to get to that number.
In any case, GH asked about power strips being "daisy chained" in order to get many outlets at an exhibition booth - not some great long run.
Seems some folk cannot see the distinction.
.... Phil
--------------------------------
George Herold
> >
> >Phil, (or someone) can you explain about the daisy chained power strips.
> >We got yelled at, at a trade show, but never quite understood the explanation.
> >
> >There's a short in something on the end of the chain...
> >Then.?
>
> An ordinary fuse needs a short circuit current that is several times
> the fuse nominal current in order to blow in a few seconds. With only
> twice the nominal current, it takes many minutes before the fuse
> blows.
>
> The short circuit current depends on the distribution transformer
> secondary output voltage and the _total_ loop resistance. The worst
> case loop resistance consist of the transformer to house, internal
> wiring in the house to the mains socket, the extension cord(s)
> resistance to the load connected to last extension cord. Multiply this
> resistance by two, to include both the Live and Neutral wire. With a
> short at the furthest point, this is the total loop resistance as seen
> from the distribution transformer.
>
> Assuming that a 5x nominal current will blow the fuse fast enough, in
> 230 V land with typically 10 A fuses, the _total_ loop resistance must
> be less than 5 ohms.
>
In any case, GH asked about power strips being "daisy chained" in order to get many outlets at an exhibition booth - not some great long run.
Seems some folk cannot see the distinction.
.... Phil
Lasse Langwadt Christensen
Dec 30, 2017, 10:50:05 AM12/30/17
to
Den lørdag den 30. december 2017 kl. 02.03.34 UTC+1 skrev Phil Allison:
> George Herold wrote:
>
> ----------------------
> >
> >
> > Phil, (or someone) can you explain about the daisy chained power strips.
> > We got yelled at, at a trade show, but never quite understood the
> > explanation.
> >
> >
>
> ** Likely because it was complete bullshit.
>
> Multiple outlet strips sold here have overall 10Amp thermal breakers installed, to protect cabling and limit the chances of tripping a remote breaker.
here the only type of extension cord that might have a thermal breaker is the reel type where people might cook it using it rolled up
> George Herold wrote:
>
> ----------------------
> >
> >
> > Phil, (or someone) can you explain about the daisy chained power strips.
> > We got yelled at, at a trade show, but never quite understood the
> > explanation.
> >
> >
>
> ** Likely because it was complete bullshit.
>
> Multiple outlet strips sold here have overall 10Amp thermal breakers installed, to protect cabling and limit the chances of tripping a remote breaker.
>
> The only safety issue I see is having too many safety ground links in series that ALL must work for the installation to be safe.
>
upsid...@downunder.com
Dec 30, 2017, 3:12:46 PM12/30/17
to
nominal current. In order to blow the fuse in less than a second (a
few mains cycles) a 10x short circuit is required.
For a 230 V system, less than the following loop resistances are
required.
10 A fuse 5x: 4.6 ohms
16 A fuse 5 x: 2.9 ohms
10 A fuse 10x: 2.3 ohms
16 A fuse 10x: 1.4 ohms
A 1 m copper conductor with 1 mm² cross section will have a resistance
of 14 mOhms. Thus a 100 m long extension cord will have a loop
resistance of 2 x 100 m x 14 mOhms/m or 2.8 ohms.
Such extension cord requires several seconds to blow the 10 or 16 A
nominal fuse.
>In any case, GH asked about power strips being "daisy chained" in order to get many outlets at an exhibition booth - not some great long run.
To my understanding "daisy chaining" refers to something like 10Base2
(thin wire) ethernet in which there is a RG58 cable between each
station T-connector.
If the OP really asked about a tree structure with multiple branches,
i.e a singe multiple socket extension cable and a short multisocket
extension cables connected to each socket in the primary extension
cord so with 5 socket extension cords you get 5 x 4 = 25 sockets.
Some standard organisations seem to think that if the end user sees a
socket into which you can mechanically plug a 10 or 16 A load that the
customer will connect 25 such 10/16 A loads into the network causing a
250/400 A current drawn from the primary extension cord and hence
causing a fire hazard. However, even if the end user would make such
stupid thing, the fuse feeding the original extension cord should
blow, protecting the house for sny fire hazards.
tabb...@gmail.com
Dec 30, 2017, 6:20:22 PM12/30/17
to
ehsjr
Dec 30, 2017, 7:00:13 PM12/30/17
to
On 12/29/2017 6:48 PM, George Herold wrote:
<snip>
>>
>> So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
>
> Phil, (or someone) can you explain about the daisy chained power strips.
> We got yelled at, at a trade show, but never quite understood the explanation.
>
> There's a short in something on the end of the chain...
> Then.?
>
> Thanks,
> George H.
Here's a link to a power strip rated 10 amps:
https://www.amazon.com/GOGOLUCK-Strips-Outlets-Protector-Extension/dp/B077QLW2S5/ref=sr_1_20_sspa?ie=UTF8&qid=1514676442&sr=8-20-spons&keywords=power+strip+bulk&psc=1#CustomerImages
I'll draw 13 amp rated power strips below:
panel
20 amp ==powerstrip1==powerstrip2==powerstrip3==powerstrip4==powerstrip5
5 amp loads plugged into power strips 2,3,4 and 5 = 20 amps total,
breaker does not trip. Power strip 1, rated at 13 amps, "sees" a 20 amp
load, overheats.
Same for daisy chained extensions:
http://www.truevalue.com/product/Extension-Cord-16-2-SPT-2-Brown-Polarized-Cube-Tap-6-Ft-/20002.uts#fullDescription
20 amp ==ext1==ext2==ext3==ext4==etc
The cumulative current flows through extension cord 1, rated for 13A
(see link above) overheating it.
Here's what daisy chaining can look like:
https://static1.squarespace.com/static/52a8a4aee4b028f890dc81ce/52aa2539e4b0f7406a36e62b/55350eb7e4b0cb1542b01a6b/1429559448727/?format=1500w
Here's a good read:
http://www.dwginc.com/news/2015/4/20/dwg-saving-the-world-one-power-strip-at-a-time
And another good read:
http://grassroots.ca/suggestions-tips-15-extension-cords-power-bars-plug-in-tap-outlets/
And here's some images that can stand your hair on end:
https://www.google.com/search?q=daisy+chained+extension+cords&tbm=isch&tbs=rimg:Cf7oIEs8aivSIjiyiJuUUT7qlyZuTofpxlMWUlbpBloSE1eg2hYpMxvxDd2kmogZBQJ3TK7lWjn2fHniVQrt1zGFDyoSCbKIm5RRPuqXETsQ_1mVJ4PehKhIJJm5Oh-nGUxYRMY4WXXeeqjMqEglSVukGWhITVxEfOQ1MQje_1SSoSCaDaFikzG_1ENEWQjjFebRyyQKhIJ3aSaiBkFAncR3Ksft0RkwHcqEglMruVaOfZ8eRHkt8SR_1TsV6SoSCeJVCu3XMYUPEa5cGFs3J0W1&tbo=u&sa=X&ved=0ahUKEwiK8O7_9rLYAhXSkeAKHdecCOIQ9C8IHg&biw=1024&bih=433&dpr=1.25
It's especially chilling when you've actually seen that crap.
Ed
<snip>
>>
>> So I gather. See the comment about daisy-chained extension cords above. That's a well-known way of burning down buildings, even without deliberately shorting the mains to ground.
>
> Phil, (or someone) can you explain about the daisy chained power strips.
> We got yelled at, at a trade show, but never quite understood the explanation.
>
> There's a short in something on the end of the chain...
> Then.?
>
> Thanks,
> George H.
https://www.amazon.com/GOGOLUCK-Strips-Outlets-Protector-Extension/dp/B077QLW2S5/ref=sr_1_20_sspa?ie=UTF8&qid=1514676442&sr=8-20-spons&keywords=power+strip+bulk&psc=1#CustomerImages
I'll draw 13 amp rated power strips below:
panel
20 amp ==powerstrip1==powerstrip2==powerstrip3==powerstrip4==powerstrip5
5 amp loads plugged into power strips 2,3,4 and 5 = 20 amps total,
breaker does not trip. Power strip 1, rated at 13 amps, "sees" a 20 amp
load, overheats.
Same for daisy chained extensions:
http://www.truevalue.com/product/Extension-Cord-16-2-SPT-2-Brown-Polarized-Cube-Tap-6-Ft-/20002.uts#fullDescription
20 amp ==ext1==ext2==ext3==ext4==etc
The cumulative current flows through extension cord 1, rated for 13A
(see link above) overheating it.
Here's what daisy chaining can look like:
https://static1.squarespace.com/static/52a8a4aee4b028f890dc81ce/52aa2539e4b0f7406a36e62b/55350eb7e4b0cb1542b01a6b/1429559448727/?format=1500w
Here's a good read:
http://www.dwginc.com/news/2015/4/20/dwg-saving-the-world-one-power-strip-at-a-time
And another good read:
http://grassroots.ca/suggestions-tips-15-extension-cords-power-bars-plug-in-tap-outlets/
And here's some images that can stand your hair on end:
https://www.google.com/search?q=daisy+chained+extension+cords&tbm=isch&tbs=rimg:Cf7oIEs8aivSIjiyiJuUUT7qlyZuTofpxlMWUlbpBloSE1eg2hYpMxvxDd2kmogZBQJ3TK7lWjn2fHniVQrt1zGFDyoSCbKIm5RRPuqXETsQ_1mVJ4PehKhIJJm5Oh-nGUxYRMY4WXXeeqjMqEglSVukGWhITVxEfOQ1MQje_1SSoSCaDaFikzG_1ENEWQjjFebRyyQKhIJ3aSaiBkFAncR3Ksft0RkwHcqEglMruVaOfZ8eRHkt8SR_1TsV6SoSCeJVCu3XMYUPEa5cGFs3J0W1&tbo=u&sa=X&ved=0ahUKEwiK8O7_9rLYAhXSkeAKHdecCOIQ9C8IHg&biw=1024&bih=433&dpr=1.25
It's especially chilling when you've actually seen that crap.
Ed
Phil Allison
Dec 30, 2017, 7:34:00 PM12/30/17
to
upsid...@downunder.com wrote:
--------------------------------
> >
> >
> >> >
> >> >Phil, (or someone) can you explain about the daisy chained power strips.
> >> >We got yelled at, at a trade show, but never quite understood the explanation.
> >> >
> >> >There's a short in something on the end of the chain...
> >> >Then.?
> >>
> >> An ordinary fuse needs a short circuit current that is several times
> >> the fuse nominal current in order to blow in a few seconds. With only
> >> twice the nominal current, it takes many minutes before the fuse
> >> blows.
> >>
> >> The short circuit current depends on the distribution transformer
> >> secondary output voltage and the _total_ loop resistance. The worst
> >> case loop resistance consist of the transformer to house, internal
> >> wiring in the house to the mains socket, the extension cord(s)
> >> resistance to the load connected to last extension cord. Multiply this
> >> resistance by two, to include both the Live and Neutral wire. With a
> >> short at the furthest point, this is the total loop resistance as seen
> >> from the distribution transformer.
> >>
> >> Assuming that a 5x nominal current will blow the fuse fast enough, in
> >> 230 V land with typically 10 A fuses, the _total_ loop resistance must
> >> be less than 5 ohms.
> >>
> >
> >
> >** FYI it takes over 100m of regular extension cable /cables to get to that number.
>
>
> For a typical residential fuse, it takes a few seconds to blow at 5x
> nominal current. In order to blow the fuse in less than a second (a
> few mains cycles) a 10x short circuit is required.
>
** Australia does not use fuses in residential installations - it's either a thermal/magnetic breaker OR a piece of "16 A fuse wire" in a ceramic holder.
16A fuse wire holds at 35A for a long time, but opens at 45A in a second.
So 5 ohms max loop impedance is realistic.
Same number YOU posted - dickhead.
> A 1 m copper conductor with 1 mm² cross section will have a resistance
> of 14 mOhms.
** The correct number is 17.5mohms.
> Thus a 100 m long extension cord will have a loop
> resistance of 2 x 100 m x 14 mOhms/m or 2.8 ohms.
>
** The correct answer is 3.5 ohms at room temp, 4.2 ohms at rated temp of 75C.
> Such extension cord requires several seconds to blow the 10 or 16 A
> nominal fuse.
** Wrong again, it will be much quicker.
>
> >In any case, GH asked about power strips being "daisy chained" in order to get many outlets at an exhibition booth - not some great long run.
>
> There seems to be some disagreement about terms used.
>
** Not when you include the context - fuckhead.
> To my understanding "daisy chaining" refers to something like 10Base2
> (thin wire) ethernet in which there is a RG58 cable between each
> station T-connector.
>
** Utterly irrelevant.
> If the OP really asked about a tree structure with multiple branches,
** NO - a simple "daisy chain" where one outlet on each strip is used to power another strip. Each strip having it own thermal breaker or HRC fuse if in the UK.
** Seems some folk cannot see the distinction.
Fuckheads like YOU for example.
.... Phil
--------------------------------
> >
> >
> >> >
> >> >Phil, (or someone) can you explain about the daisy chained power strips.
> >> >We got yelled at, at a trade show, but never quite understood the explanation.
> >> >
> >> >There's a short in something on the end of the chain...
> >> >Then.?
> >>
> >> An ordinary fuse needs a short circuit current that is several times
> >> the fuse nominal current in order to blow in a few seconds. With only
> >> twice the nominal current, it takes many minutes before the fuse
> >> blows.
> >>
> >> The short circuit current depends on the distribution transformer
> >> secondary output voltage and the _total_ loop resistance. The worst
> >> case loop resistance consist of the transformer to house, internal
> >> wiring in the house to the mains socket, the extension cord(s)
> >> resistance to the load connected to last extension cord. Multiply this
> >> resistance by two, to include both the Live and Neutral wire. With a
> >> short at the furthest point, this is the total loop resistance as seen
> >> from the distribution transformer.
> >>
> >> Assuming that a 5x nominal current will blow the fuse fast enough, in
> >> 230 V land with typically 10 A fuses, the _total_ loop resistance must
> >> be less than 5 ohms.
> >>
> >
> >
> >** FYI it takes over 100m of regular extension cable /cables to get to that number.
>
>
> For a typical residential fuse, it takes a few seconds to blow at 5x
> nominal current. In order to blow the fuse in less than a second (a
> few mains cycles) a 10x short circuit is required.
>
16A fuse wire holds at 35A for a long time, but opens at 45A in a second.
So 5 ohms max loop impedance is realistic.
Same number YOU posted - dickhead.
> A 1 m copper conductor with 1 mm² cross section will have a resistance
> of 14 mOhms.
> Thus a 100 m long extension cord will have a loop
> resistance of 2 x 100 m x 14 mOhms/m or 2.8 ohms.
>
> Such extension cord requires several seconds to blow the 10 or 16 A
> nominal fuse.
>
> >In any case, GH asked about power strips being "daisy chained" in order to get many outlets at an exhibition booth - not some great long run.
>
> There seems to be some disagreement about terms used.
>
> To my understanding "daisy chaining" refers to something like 10Base2
> (thin wire) ethernet in which there is a RG58 cable between each
> station T-connector.
>
> If the OP really asked about a tree structure with multiple branches,
** Seems some folk cannot see the distinction.
Fuckheads like YOU for example.
.... Phil
ehsjr
Dec 30, 2017, 7:45:04 PM12/30/17
to
On 12/28/2017 6:25 PM, tabb...@gmail.com wrote:
> On Thursday, 28 December 2017 22:43:05 UTC, pcdh...@gmail.com wrote:
>> NT:
>>> On Thursday, 28 December 2017 20:27:43 UTC, pcdh...@gmail.com wrote:
>
>>>>> You might limit the current and trip the mains breaker to cope with the
>>>>> short. That way you simultaneously protect the shorted device and send
>>>>> users a dramatic message that something's wrong.
>>>
>>>> You mean the breaker at the _panel_? How do you know if it's magnetic or thermal?
>>>>
>>>> And then somebody plugs it into daisy-chained extension cords and your 'safety
>>>> device' burns down the building. Brilliant all round. :(
>>
>>> don't implement it stupidly. The current limiter must have overheat protection.
>>
>> How are you going to do that if you don't know how it's connected?
>
> I'm not making sense of that question
>
>> Building a known fast breaker into the box, I get. Relying on the capabilities of a hypothetical breaker at an unknown upstream point, not so much.
>>
>> Cheers
>>
>> Phil Hobbs
>
> Mains supply breakers aren't hypothetical. In UK they're well defined. I presume they are in all other 1st world countries too.
>
The mains supply breaker is NOT intended nor designed to protect the
> On Thursday, 28 December 2017 22:43:05 UTC, pcdh...@gmail.com wrote:
>> NT:
>>> On Thursday, 28 December 2017 20:27:43 UTC, pcdh...@gmail.com wrote:
>
>>>>> You might limit the current and trip the mains breaker to cope with the
>>>>> short. That way you simultaneously protect the shorted device and send
>>>>> users a dramatic message that something's wrong.
>>>
>>>> You mean the breaker at the _panel_? How do you know if it's magnetic or thermal?
>>>>
>>>> And then somebody plugs it into daisy-chained extension cords and your 'safety
>>>> device' burns down the building. Brilliant all round. :(
>>
>>> don't implement it stupidly. The current limiter must have overheat protection.
>>
>> How are you going to do that if you don't know how it's connected?
>
> I'm not making sense of that question
>
>> Building a known fast breaker into the box, I get. Relying on the capabilities of a hypothetical breaker at an unknown upstream point, not so much.
>>
>> Cheers
>>
>> Phil Hobbs
>
> Mains supply breakers aren't hypothetical. In UK they're well defined. I presume they are in all other 1st world countries too.
>
power using equipment. That breaker is there to protect the permanent
wiring from the panel to the outlet to which the power using equipment
is connected. Relying on the mains breaker to make the power using
equipment safe in the event of a fault in that equipment is wrong,
unsafe and stupid everywhere, and is illegal in the USA.
> And the whole point of overheat cutout is that it interrupts the current if for any reason the supply fails to. That could be as simple as a fusible resistor.
>
must be designed to interrupt the current before the mains supply
over-current device does. You must NOT rely on the mains panel breaker
to protect the equipment, or personnel using the equipment. The
panel breaker's job is to protect the building wiring up to the
point where the external equipment draws power from it.
Ed
>
> NT
>
Phil Allison
Dec 30, 2017, 7:52:32 PM12/30/17
to
ehsjr troll wrote:
----------------
>
> The mains supply breaker is NOT intended nor designed to protect the
> power using equipment. That breaker is there to protect the permanent
> wiring from the panel to the outlet to which the power using equipment
> is connected.
>
** Essentially true, but the nest bit is not.
> Relying on the mains breaker to make the power using
> equipment safe in the event of a fault in that equipment is wrong,
> unsafe and stupid everywhere,
** Bollocks.
> and is illegal in the USA.
** Really ??
So all US appliances have fuses fitted ??
.... Phil
----------------
>
> The mains supply breaker is NOT intended nor designed to protect the
> power using equipment. That breaker is there to protect the permanent
> wiring from the panel to the outlet to which the power using equipment
> is connected.
>
> Relying on the mains breaker to make the power using
> equipment safe in the event of a fault in that equipment is wrong,
> unsafe and stupid everywhere,
> and is illegal in the USA.
So all US appliances have fuses fitted ??
.... Phil
ehsjr
Dec 30, 2017, 11:14:41 PM12/30/17
to
as the UL (Underwriters Laboratory) (or other accepted testing lab)
the lab is saying, in effect, it was manufactured in accordance with
the rules and meets electrical (and other) safety requirements. If
a fuse (or breaker or whatever) is required and the device doesn't
have it, it won't be listed, nor will it be legal for the manufacturer
to sell it in the US.
You could spend months reading all the applicable rules and regulations
concerning product electrical safety, but I believe the precis above
captures the essence. If you want to do some wading through it, it's
probably best to start with the NEC and the UL White Book.
(links below)
Ed
You can wade through the wording of our National Electrical Code
article 90-7 (et al) if you like:
https://www.mikeholt.com/mojonewsarchive/EES-HTML/HTML/LabeledListedNECOSHA~20030107.htm
and the UL white book:
https://www.ul.com/wp-content/uploads/2014/09/UL-White-Book.pdf?utm_source=multiple&utm_medium=vanity&utm_campaign=codeauthoritieswhitebook
>
>
> .... Phil
>
Phil Allison
Dec 30, 2017, 11:33:47 PM12/30/17
to
ehsjr TROLL wrote:
-------------------------
> If the equipment is listed by a certified testing laboratory such
> as the UL (Underwriters Laboratory)
** Non compulsory, AFAIK.
Wot a load of crapology.
.... Phil
-------------------------
>
>
> >>
> >> The mains supply breaker is NOT intended nor designed to protect the
> >> power using equipment. That breaker is there to protect the permanent
> >> wiring from the panel to the outlet to which the power using equipment
> >> is connected.
> >>
> >
> > ** Essentially true, but the next bit is not.
>
> >>
> >> The mains supply breaker is NOT intended nor designed to protect the
> >> power using equipment. That breaker is there to protect the permanent
> >> wiring from the panel to the outlet to which the power using equipment
> >> is connected.
> >>
> >
> >
> >
> >> Relying on the mains breaker to make the power using
> >> equipment safe in the event of a fault in that equipment is wrong,
> >> unsafe and stupid everywhere,
> >
> >
> > ** Bollocks.
> >
> >
> >
> >> and is illegal in the USA.
> >
> >
> >
> > ** Really ??
> >
> > So all US appliances have fuses fitted ??
>
>
> No.
** Then at least some of them are dangerous - according to YOU.
> >
> >> Relying on the mains breaker to make the power using
> >> equipment safe in the event of a fault in that equipment is wrong,
> >> unsafe and stupid everywhere,
> >
> >
> > ** Bollocks.
> >
> >
> >
> >> and is illegal in the USA.
> >
> >
> >
> > ** Really ??
> >
> > So all US appliances have fuses fitted ??
>
>
> No.
> If the equipment is listed by a certified testing laboratory such
> as the UL (Underwriters Laboratory)
Wot a load of crapology.
.... Phil
Phil Allison
Dec 31, 2017, 12:13:36 AM12/31/17
to
ehsjr TROLL wrote:
------------------
>
> Here's a link to a power strip rated 10 amps:
> https://www.amazon.com/GOGOLUCK-Strips-Outlets-Protector-Extension/dp/B077QLW2S5/ref=sr_1_20_sspa?ie=UTF8&qid=1514676442&sr=8-20-spons&keywords=power+strip+bulk&psc=1#CustomerImages
>
> I'll draw 13 amp rated power strips below:
>
> panel
> 20 amp ==powerstrip1==powerstrip2==powerstrip3==powerstrip4==powerstrip5
>
> 5 amp loads plugged into power strips 2,3,4 and 5 = 20 amps total,
> breaker does not trip. Power strip 1, rated at 13 amps, "sees" a 20 amp
> load, overheats.
>
** So fucking what ?
Plug two 10 amp loads into ONE strip and you have a similar overload.
Power strips SHOULD all have thermal beakers included, been the law here for over 20 years. You Yanks are behind the times.
FYI:
Cable rated at 13amps ( ie 16G) will not melt & burn at 20amps - it merely gets a bit warmer. There is a LARGE safety factor included in all cable and mains power plug/socket ratings.
FYI:
I did some bench tests not long ago using 10amp (1sqmm) mains cable, deliberately overloading it:
At rated load it was just warm ( circa 15C temp rise)
At 2x rated, it was quite warm ( circa 35C temp rise).
At 3x rated the plastic softened and it was a bit too hot to touch.
I used a K-thermocouple to monitor temps.
> Same for daisy chained extensions:
** Same reply.
No such issue exists in the UK or Australia.
George Herold lives in the UK.
.... Phil
------------------
>
> Here's a link to a power strip rated 10 amps:
> https://www.amazon.com/GOGOLUCK-Strips-Outlets-Protector-Extension/dp/B077QLW2S5/ref=sr_1_20_sspa?ie=UTF8&qid=1514676442&sr=8-20-spons&keywords=power+strip+bulk&psc=1#CustomerImages
>
> I'll draw 13 amp rated power strips below:
>
> panel
> 20 amp ==powerstrip1==powerstrip2==powerstrip3==powerstrip4==powerstrip5
>
> 5 amp loads plugged into power strips 2,3,4 and 5 = 20 amps total,
> breaker does not trip. Power strip 1, rated at 13 amps, "sees" a 20 amp
> load, overheats.
>
Plug two 10 amp loads into ONE strip and you have a similar overload.
Power strips SHOULD all have thermal beakers included, been the law here for over 20 years. You Yanks are behind the times.
FYI:
Cable rated at 13amps ( ie 16G) will not melt & burn at 20amps - it merely gets a bit warmer. There is a LARGE safety factor included in all cable and mains power plug/socket ratings.
FYI:
I did some bench tests not long ago using 10amp (1sqmm) mains cable, deliberately overloading it:
At rated load it was just warm ( circa 15C temp rise)
At 2x rated, it was quite warm ( circa 35C temp rise).
At 3x rated the plastic softened and it was a bit too hot to touch.
I used a K-thermocouple to monitor temps.
> Same for daisy chained extensions:
No such issue exists in the UK or Australia.
George Herold lives in the UK.
.... Phil
Piotr Wyderski
Dec 31, 2017, 4:57:35 AM12/31/17
to
Piglet wrote:
> Exactly. Fast turn off makes possible something not possible before.
On the other hand, fast turn-off is necessary in the case of MOSFETs.
> Exactly. Fast turn off makes possible something not possible before.
The SOAs invariably end at the 10us limit for short-circuit currents
and you don't have much time for any form of sophisticated analysis.
Most often a window comparator, so the device is necessarily on a,
erm, short fuse. This can be a drawback, because the value of I
doesn't matter that much, its I^2*R what causes damage.
> So which is better, a few milli-seconds of hundreds of amperes and which
> causes a clearly identifiable indication of fault requiring manual
> intervention to reset - or - a few tens of micro-seconds of tens of
> amperes and a circuit that automatically resumes when the fault is cleared?
Best regards, Piotr
Piotr Wyderski
Dec 31, 2017, 5:29:18 AM12/31/17
to
pcdh...@gmail.com wrote:
> Or the wiring might be marginal, but good enough for many more years unless somebody did something idiotic like shorting the mains.
I'd say that the short-circuit behaviour of the mains is one of the
> Or the wiring might be marginal, but good enough for many more years unless somebody did something idiotic like shorting the mains.
most important parameters of the wiring. In Poland exactly this
parameter (the short-circuit loop resistance) must be measured every
5 years by a qualified technician in order to allow the further
operation of the flat/house installation. The wiring just can't be
barely enough, something in the order of 5-10x current capacity
for a short period must be ensured in order to make the fuses blow.
My worst-case is 0.5Ohm, with 0.38Ohm being the most frequent value.
Best regards, Piotr
upsid...@downunder.com
Dec 31, 2017, 7:12:35 AM12/31/17
to
upsid...@downunder.com
Dec 31, 2017, 7:36:35 AM12/31/17
to
On Sat, 30 Dec 2017 21:13:27 -0800 (PST), Phil Allison
<palli...@gmail.com> wrote:
>ehsjr TROLL wrote:
>
>------------------
>
>>
>> Here's a link to a power strip rated 10 amps:
>> https://www.amazon.com/GOGOLUCK-Strips-Outlets-Protector-Extension/dp/B077QLW2S5/ref=sr_1_20_sspa?ie=UTF8&qid=1514676442&sr=8-20-spons&keywords=power+strip+bulk&psc=1#CustomerImages
>>
>> I'll draw 13 amp rated power strips below:
>>
>> panel
>> 20 amp ==powerstrip1==powerstrip2==powerstrip3==powerstrip4==powerstrip5
>>
>> 5 amp loads plugged into power strips 2,3,4 and 5 = 20 amps total,
>> breaker does not trip. Power strip 1, rated at 13 amps, "sees" a 20 amp
>> load, overheats.
>>
>
>** So fucking what ?
>
>Plug two 10 amp loads into ONE strip and you have a similar overload.
>
>Power strips SHOULD all have thermal beakers included, been the law here for over 20 years. You Yanks are behind the times.
What is the point of including an overcurrent device in the power
<palli...@gmail.com> wrote:
>ehsjr TROLL wrote:
>
>------------------
>
>>
>> Here's a link to a power strip rated 10 amps:
>> https://www.amazon.com/GOGOLUCK-Strips-Outlets-Protector-Extension/dp/B077QLW2S5/ref=sr_1_20_sspa?ie=UTF8&qid=1514676442&sr=8-20-spons&keywords=power+strip+bulk&psc=1#CustomerImages
>>
>> I'll draw 13 amp rated power strips below:
>>
>> panel
>> 20 amp ==powerstrip1==powerstrip2==powerstrip3==powerstrip4==powerstrip5
>>
>> 5 amp loads plugged into power strips 2,3,4 and 5 = 20 amps total,
>> breaker does not trip. Power strip 1, rated at 13 amps, "sees" a 20 amp
>> load, overheats.
>>
>
>** So fucking what ?
>
>Plug two 10 amp loads into ONE strip and you have a similar overload.
>
>Power strips SHOULD all have thermal beakers included, been the law here for over 20 years. You Yanks are behind the times.
strip end of the extension cable ?
In countries using ring mains (such as the UK) There is a single loop
of heavy wire zig-zagging around the building with big e.g. 35 A fuses
at each end of the loop.
Each device to be plugged into the ring mains loop socket must have a
fuse in the plug. Thus, the extension cable plug end should have a 13
or 20 A overcurrent protector, not the power strip end.
Phil Allison
Dec 31, 2017, 7:47:35 AM12/31/17
to
upsid...@downunder.com wrote:
--------------------------------
>
> What is the point of including an overcurrent device in the power
> strip end of the extension cable ?
>
** You tell us - seeing as you invented the idea.
Seriously, you have lost contact with any prior context and are raving like a mad man.
> In countries using ring mains (such as the UK) There is a single loop
> of heavy wire zig-zagging around the building with big e.g. 35 A fuses
> at each end of the loop.
>
** Just one breaker of fuse is used for each ring.
Are you on drugs ?
> Each device to be plugged into the ring mains loop socket must have a
> fuse in the plug. Thus, the extension cable plug end should have a 13
> or 20 A overcurrent protector, not the power strip end.
>
** No-one here has said otherwise.
You good at shadow boxing, by any chance ?
.... Phil
--------------------------------
>
> What is the point of including an overcurrent device in the power
> strip end of the extension cable ?
>
Seriously, you have lost contact with any prior context and are raving like a mad man.
> In countries using ring mains (such as the UK) There is a single loop
> of heavy wire zig-zagging around the building with big e.g. 35 A fuses
> at each end of the loop.
>
Are you on drugs ?
> Each device to be plugged into the ring mains loop socket must have a
> fuse in the plug. Thus, the extension cable plug end should have a 13
> or 20 A overcurrent protector, not the power strip end.
>
You good at shadow boxing, by any chance ?
.... Phil
tabb...@gmail.com
Dec 31, 2017, 8:51:31 AM12/31/17
to
On Sunday, 31 December 2017 00:45:04 UTC, ehsjr wrote:
> That breaker is there to protect the permanent
> wiring from the panel to the outlet to which the power using equipment
> is connected. Relying on the mains breaker to make the power using
> equipment safe in the event of a fault in that equipment is wrong,
> unsafe and stupid everywhere, and is illegal in the USA.
you guys seem determined to not get it. Protection can be split between 2 devices, as long as in all scenarios safe protection occurs. That CAN be done, and safely, by using the breaker to trip in some situations. Splitting the protection happens day in day out over here.
> > And the whole point of overheat cutout is that it interrupts the current if for any reason the supply fails to. That could be as simple as a fusible resistor.
> >
>
> No. The overheat cutout, or any other equipment power safety device,
> must be designed to interrupt the current before the mains supply
> over-current device does. You must NOT rely on the mains panel breaker
> to protect the equipment, or personnel using the equipment. The
> panel breaker's job is to protect the building wiring up to the
> point where the external equipment draws power from it.
I guess you're in America. I'm not.
NT
> On 12/28/2017 6:25 PM, tabbypurr wrote:
> > On Thursday, 28 December 2017 22:43:05 UTC, pcdh...@gmail.com wrote:
> >> NT:
> >>> On Thursday, 28 December 2017 20:27:43 UTC, pcdh...@gmail.com wrote:
> >>>>> You might limit the current and trip the mains breaker to cope with the
> >>>>> short. That way you simultaneously protect the shorted device and send
> >>>>> users a dramatic message that something's wrong.
> >>>
> >>>> You mean the breaker at the _panel_? How do you know if it's magnetic or thermal?
> >>>>
> >>>> And then somebody plugs it into daisy-chained extension cords and your 'safety
> >>>> device' burns down the building. Brilliant all round. :(
> >>
> >>> don't implement it stupidly. The current limiter must have overheat protection.
> >>
> >> How are you going to do that if you don't know how it's connected?
> >
> > I'm not making sense of that question
> >
> >> Building a known fast breaker into the box, I get. Relying on the capabilities of a hypothetical breaker at an unknown upstream point, not so much.
> >>
> >> Cheers
> >>
> >> Phil Hobbs
> >
> > Mains supply breakers aren't hypothetical. In UK they're well defined. I presume they are in all other 1st world countries too.
> >
>
> The mains supply breaker is NOT intended nor designed to protect the
> power using equipment.
In the UK it sometimes does
> > On Thursday, 28 December 2017 22:43:05 UTC, pcdh...@gmail.com wrote:
> >> NT:
> >>> On Thursday, 28 December 2017 20:27:43 UTC, pcdh...@gmail.com wrote:
> >>>>> You might limit the current and trip the mains breaker to cope with the
> >>>>> short. That way you simultaneously protect the shorted device and send
> >>>>> users a dramatic message that something's wrong.
> >>>
> >>>> You mean the breaker at the _panel_? How do you know if it's magnetic or thermal?
> >>>>
> >>>> And then somebody plugs it into daisy-chained extension cords and your 'safety
> >>>> device' burns down the building. Brilliant all round. :(
> >>
> >>> don't implement it stupidly. The current limiter must have overheat protection.
> >>
> >> How are you going to do that if you don't know how it's connected?
> >
> > I'm not making sense of that question
> >
> >> Building a known fast breaker into the box, I get. Relying on the capabilities of a hypothetical breaker at an unknown upstream point, not so much.
> >>
> >> Cheers
> >>
> >> Phil Hobbs
> >
> > Mains supply breakers aren't hypothetical. In UK they're well defined. I presume they are in all other 1st world countries too.
> >
>
> The mains supply breaker is NOT intended nor designed to protect the
> power using equipment.
> That breaker is there to protect the permanent
> wiring from the panel to the outlet to which the power using equipment
> is connected. Relying on the mains breaker to make the power using
> equipment safe in the event of a fault in that equipment is wrong,
> unsafe and stupid everywhere, and is illegal in the USA.
> > And the whole point of overheat cutout is that it interrupts the current if for any reason the supply fails to. That could be as simple as a fusible resistor.
> >
>
> No. The overheat cutout, or any other equipment power safety device,
> must be designed to interrupt the current before the mains supply
> over-current device does. You must NOT rely on the mains panel breaker
> to protect the equipment, or personnel using the equipment. The
> panel breaker's job is to protect the building wiring up to the
> point where the external equipment draws power from it.
NT
tabb...@gmail.com
Dec 31, 2017, 8:54:05 AM12/31/17
to
NT
tabb...@gmail.com
Dec 31, 2017, 9:01:00 AM12/31/17
to
On Sunday, 31 December 2017 12:36:35 UTC, upsid...@downunder.com wrote:
> On Sat, 30 Dec 2017 21:13:27 -0800 (PST), Phil Allison
> On Sat, 30 Dec 2017 21:13:27 -0800 (PST), Phil Allison
> >Power strips SHOULD all have thermal beakers included, been the law here for over 20 years. You Yanks are behind the times.
most of ours don't in uk
> What is the point of including an overcurrent device in the power
> strip end of the extension cable ?
> In countries using ring mains (such as the UK) There is a single loop
> of heavy wire zig-zagging around the building with big e.g. 35 A fuses
> at each end of the loop.
> Each device to be plugged into the ring mains loop socket must have a
> fuse in the plug. Thus, the extension cable plug end should have a 13
> or 20 A overcurrent protector, not the power strip end.
NT
tabb...@gmail.com
Dec 31, 2017, 8:39:20 PM12/31/17
to
On Sunday, 31 December 2017 12:36:35 UTC, upsid...@downunder.com wrote:
> On Sat, 30 Dec 2017 21:13:27 -0800 (PST), Phil Allison
> >Power strips SHOULD all have thermal beakers included, been the law here for over 20 years. You Yanks are behind the times.
most of ours don't in uk
> What is the point of including an overcurrent device in the power
> strip end of the extension cable ?
> strip end of the extension cable ?
to stop it overheating and melting. We have them now in reel extension leads, but not others.
> In countries using ring mains (such as the UK) There is a single loop
> of heavy wire zig-zagging around the building with big e.g. 35 A fuses
> at each end of the loop.
> of heavy wire zig-zagging around the building with big e.g. 35 A fuses
> at each end of the loop.
ring circuits use a single 32A breaker or 30A fuse. Only pre-1955 installs sometimes have 2 fuses for one ring, or in some cases 4!
> Each device to be plugged into the ring mains loop socket must have a
> fuse in the plug. Thus, the extension cable plug end should have a 13
> or 20 A overcurrent protector, not the power strip end.
13A maximum
> fuse in the plug. Thus, the extension cable plug end should have a 13
> or 20 A overcurrent protector, not the power strip end.
NT
Phil Allison
Dec 31, 2017, 9:31:04 PM12/31/17
to
upsid...@downunder.com wrote:
----------------------------
>
> One way to indirectly measure th total loop resistance is to plug an
> incandescent lamp at the end of the last extension cord and then plug
> in and out some big load and observe how the lamp flickers during the
> transition. Incandescent lamps are very sensitive to small voltage
> variations. A strong variation will indicate a relatively high loop
> resistance.
>
** I like to use a 10 amp load like a fan heater of electric kettle while monitoring the voltage with a DMM.
Monitoring the wall outlet itself ( A-N )results in about 5 to 10 volts drop, so the supply impedance is 0.5 to 1 ohm. You could also monitor from N-E and double the reading.
From this you can infer the short circuit current will be between 240 and 480 amps - so will INSTANTLY trip a 16A fuse or magnetic breaker.
.... Phil
----------------------------
>
> One way to indirectly measure th total loop resistance is to plug an
> incandescent lamp at the end of the last extension cord and then plug
> in and out some big load and observe how the lamp flickers during the
> transition. Incandescent lamps are very sensitive to small voltage
> variations. A strong variation will indicate a relatively high loop
> resistance.
>
Monitoring the wall outlet itself ( A-N )results in about 5 to 10 volts drop, so the supply impedance is 0.5 to 1 ohm. You could also monitor from N-E and double the reading.
From this you can infer the short circuit current will be between 240 and 480 amps - so will INSTANTLY trip a 16A fuse or magnetic breaker.
.... Phil
Jasen Betts
Dec 31, 2017, 11:31:10 PM12/31/17
to
On 2018-01-01, tabb...@gmail.com <tabb...@gmail.com> wrote:
> On Sunday, 31 December 2017 12:36:35 UTC, upsid...@downunder.com wrote:
>> On Sat, 30 Dec 2017 21:13:27 -0800 (PST), Phil Allison
>
>
>> >Power strips SHOULD all have thermal beakers included, been the law here for over 20 years. You Yanks are behind the times.
>
> most of ours don't in uk
>
yeah, but aren't yours fused in the plug? That would be even better from a
> On Sunday, 31 December 2017 12:36:35 UTC, upsid...@downunder.com wrote:
>> On Sat, 30 Dec 2017 21:13:27 -0800 (PST), Phil Allison
>
>
>> >Power strips SHOULD all have thermal beakers included, been the law here for over 20 years. You Yanks are behind the times.
>
> most of ours don't in uk
>
safety standpoint if you discount the inconvenience of a blown fuse.
--
This email has not been checked by half-arsed antivirus software
tabb...@gmail.com
Jan 1, 2018, 12:38:53 AM1/1/18
to
On Monday, 1 January 2018 04:31:10 UTC, Jasen Betts wrote:
NT
> On 2018-01-01, tabbypurr wrote:
> > On Sunday, 31 December 2017 12:36:35 UTC, upsid...@downunder.com wrote:
> >> On Sat, 30 Dec 2017 21:13:27 -0800 (PST), Phil Allison
> >
> >
> >> >Power strips SHOULD all have thermal beakers included, been the law here for over 20 years. You Yanks are behind the times.
> >
> > most of ours don't in uk
> >
>
> yeah, but aren't yours fused in the plug? That would be even better from a
> safety standpoint if you discount the inconvenience of a blown fuse.
Every mains plug is fused here (OK there are exceptions but not that are relevant). Max 13A, also often 3A. Most sockets are on 32A rings.
> > On Sunday, 31 December 2017 12:36:35 UTC, upsid...@downunder.com wrote:
> >> On Sat, 30 Dec 2017 21:13:27 -0800 (PST), Phil Allison
> >
> >
> >> >Power strips SHOULD all have thermal beakers included, been the law here for over 20 years. You Yanks are behind the times.
> >
> > most of ours don't in uk
> >
>
> yeah, but aren't yours fused in the plug? That would be even better from a
> safety standpoint if you discount the inconvenience of a blown fuse.
NT
ehsjr
Jan 1, 2018, 6:11:14 PM1/1/18
to
On 12/30/2017 11:33 PM, Phil Allison wrote:
> ehsjr TROLL wrote:
>
> -------------------------
>>
>>
>>>>
>>>> The mains supply breaker is NOT intended nor designed to protect the
>>>> power using equipment. That breaker is there to protect the permanent
>>>> wiring from the panel to the outlet to which the power using equipment
>>>> is connected.
>>>>
>>>
>>> ** Essentially true, but the next bit is not.
>>>
>>>
>>>> Relying on the mains breaker to make the power using
>>>> equipment safe in the event of a fault in that equipment is wrong,
>>>> unsafe and stupid everywhere,
>>>
>>>
>>> ** Bollocks.
>>>
>>>
>>>
>>>> and is illegal in the USA.
>>>
>>>
>>>
>>> ** Really ??
>>>
>>> So all US appliances have fuses fitted ??
>>
>>
>> No.
>
>
> ** Then at least some of them are dangerous - according to YOU.
So you think an appliance must have a fuse must be fitted to make
> ehsjr TROLL wrote:
>
> -------------------------
>>
>>
>>>>
>>>> The mains supply breaker is NOT intended nor designed to protect the
>>>> power using equipment. That breaker is there to protect the permanent
>>>> wiring from the panel to the outlet to which the power using equipment
>>>> is connected.
>>>>
>>>
>>> ** Essentially true, but the next bit is not.
>>>
>>>
>>>> Relying on the mains breaker to make the power using
>>>> equipment safe in the event of a fault in that equipment is wrong,
>>>> unsafe and stupid everywhere,
>>>
>>>
>>> ** Bollocks.
>>>
>>>
>>>
>>>> and is illegal in the USA.
>>>
>>>
>>>
>>> ** Really ??
>>>
>>> So all US appliances have fuses fitted ??
>>
>>
>> No.
>
>
> ** Then at least some of them are dangerous - according to YOU.
it safe?
Don't be silly. Dishwashers, electric stoves, clothes washer/dryers,
refrigerators et al have grounded metal cabinets. No fuse is required
for electrical safety for people using them. Double insulated tools
prevent people from contacting an electrical fault.
Ed
Phil Allison
Jan 1, 2018, 8:26:18 PM1/1/18
to
ehsjr wrote:
----------------
>
> >>>>
> >>>> The mains supply breaker is NOT intended nor designed to protect the
> >>>> power using equipment. That breaker is there to protect the permanent
> >>>> wiring from the panel to the outlet to which the power using equipment
> >>>> is connected.
> >>>>
> >>>
> >>> ** Essentially true, but the next bit is not.
> >>>
> >>>
> >>>> Relying on the mains breaker to make the power using
> >>>> equipment safe in the event of a fault in that equipment is wrong,
> >>>> unsafe and stupid everywhere,
> >>>
> >>>
> >>> ** Bollocks.
> >>>
> >>>
> >>>
> >>>> and is illegal in the USA.
> >>>
> >>>
> >>>
> >>> ** Really ??
> >>>
> >>> So all US appliances have fuses fitted ??
> >>
> >>
> >> No.
> >
> >
> > ** Then at least some of them are dangerous - according to YOU.
>
> So you think an appliance must have a fuse must be fitted to make
> it safe?
>
** FFS - that is what **YOU** just claimed.
----------------
>
> >>>>
> >>>> The mains supply breaker is NOT intended nor designed to protect the
> >>>> power using equipment. That breaker is there to protect the permanent
> >>>> wiring from the panel to the outlet to which the power using equipment
> >>>> is connected.
> >>>>
> >>>
> >>> ** Essentially true, but the next bit is not.
> >>>
> >>>
> >>>> Relying on the mains breaker to make the power using
> >>>> equipment safe in the event of a fault in that equipment is wrong,
> >>>> unsafe and stupid everywhere,
> >>>
> >>>
> >>> ** Bollocks.
> >>>
> >>>
> >>>
> >>>> and is illegal in the USA.
> >>>
> >>>
> >>>
> >>> ** Really ??
> >>>
> >>> So all US appliances have fuses fitted ??
> >>
> >>
> >> No.
> >
> >
> > ** Then at least some of them are dangerous - according to YOU.
>
> So you think an appliance must have a fuse must be fitted to make
> it safe?
>
I say your original premise is FALSE.
> Don't be silly. Dishwashers, electric stoves, clothes washer/dryers,
> refrigerators et al have grounded metal cabinets. No fuse is required
> for electrical safety for people using them.
That was never the question - you desperate, damn LIAR.
Fuses and breakers provide NO protection against electric shock.
They provide minimal, fire hazard protection and little more.
FYI dickhead:
Earthing of metal cases provides shock protection ONLY if the metal really IS earthed. Lotsa ways it can wind up live instead.
User replaceable fuses cannot be relied on to provide protection of any kind.
Installed breakers provide fire protection for installed cables and appliance cables in the vast majority of situations too - but no fire protection for appliances themselves.
Go away you damn fool.
.... Phil
tabb...@gmail.com
Jan 1, 2018, 9:51:38 PM1/1/18
to
On Tuesday, 2 January 2018 01:26:18 UTC, Phil Allison wrote:
> ehsjr wrote:
8<
> > > ** Then at least some of them are dangerous - according to YOU.
> >
> > So you think an appliance must have a fuse must be fitted to make
> > it safe?
> >
>
>
> ** FFS - that is what **YOU** just claimed.
>
> I say your original premise is FALSE.
>
>
>
> > Don't be silly. Dishwashers, electric stoves, clothes washer/dryers,
> > refrigerators et al have grounded metal cabinets. No fuse is required
> > for electrical safety for people using them.
>
>
> ** MASSIVE RED HERRING ALERT !!!!!!!!!!!!!!!!!!!!!
>
> That was never the question - you desperate, damn LIAR.
He's just trolling.
> Fuses and breakers provide NO protection against electric shock.
>
> They provide minimal, fire hazard protection and little more.
>
>
> FYI dickhead:
>
> Earthing of metal cases provides shock protection ONLY if the metal really IS earthed. Lotsa ways it can wind up live instead.
>
> User replaceable fuses cannot be relied on to provide protection of any kind.
>
> Installed breakers provide fire protection for installed cables and appliance cables in the vast majority of situations too - but no fire protection for appliances themselves.
>
> Go away you damn fool.
>
>
>
> .... Phil
but that section contains errors. I don't expect any reasonable response from you, hence it's not even worth getting into it.
> ehsjr wrote:
8<
> > > ** Then at least some of them are dangerous - according to YOU.
> >
> > So you think an appliance must have a fuse must be fitted to make
> > it safe?
> >
>
>
> ** FFS - that is what **YOU** just claimed.
>
> I say your original premise is FALSE.
>
>
>
> > Don't be silly. Dishwashers, electric stoves, clothes washer/dryers,
> > refrigerators et al have grounded metal cabinets. No fuse is required
> > for electrical safety for people using them.
>
>
> ** MASSIVE RED HERRING ALERT !!!!!!!!!!!!!!!!!!!!!
>
> That was never the question - you desperate, damn LIAR.
> Fuses and breakers provide NO protection against electric shock.
>
> They provide minimal, fire hazard protection and little more.
>
>
> FYI dickhead:
>
> Earthing of metal cases provides shock protection ONLY if the metal really IS earthed. Lotsa ways it can wind up live instead.
>
> User replaceable fuses cannot be relied on to provide protection of any kind.
>
> Installed breakers provide fire protection for installed cables and appliance cables in the vast majority of situations too - but no fire protection for appliances themselves.
>
> Go away you damn fool.
>
>
>
> .... Phil
ehsjr
Jan 1, 2018, 10:25:12 PM1/1/18
to
On 12/31/2017 12:13 AM, Phil Allison wrote:
> ehsjr TROLL wrote:
>
> ------------------
>
>>
>> Here's a link to a power strip rated 10 amps:
>> https://www.amazon.com/GOGOLUCK-Strips-Outlets-Protector-Extension/dp/B077QLW2S5/ref=sr_1_20_sspa?ie=UTF8&qid=1514676442&sr=8-20-spons&keywords=power+strip+bulk&psc=1#CustomerImages
>>
>> I'll draw 13 amp rated power strips below:
>>
>> panel
>> 20 amp ==powerstrip1==powerstrip2==powerstrip3==powerstrip4==powerstrip5
>>
>> 5 amp loads plugged into power strips 2,3,4 and 5 = 20 amps total,
>> breaker does not trip. Power strip 1, rated at 13 amps, "sees" a 20 amp
>> load, overheats.
>>
>
> ** So fucking what ?
> ehsjr TROLL wrote:
>
> ------------------
>
>>
>> Here's a link to a power strip rated 10 amps:
>> https://www.amazon.com/GOGOLUCK-Strips-Outlets-Protector-Extension/dp/B077QLW2S5/ref=sr_1_20_sspa?ie=UTF8&qid=1514676442&sr=8-20-spons&keywords=power+strip+bulk&psc=1#CustomerImages
>>
>> I'll draw 13 amp rated power strips below:
>>
>> panel
>> 20 amp ==powerstrip1==powerstrip2==powerstrip3==powerstrip4==powerstrip5
>>
>> 5 amp loads plugged into power strips 2,3,4 and 5 = 20 amps total,
>> breaker does not trip. Power strip 1, rated at 13 amps, "sees" a 20 amp
>> load, overheats.
>>
>
> ** So fucking what ?
"Phil, (or someone) can you explain about the daisy chained power strips.
We got yelled at, at a trade show, but never quite understood the
explanation."
That is the "so ******* what ?": it's an answer to the question
We got yelled at, at a trade show, but never quite understood the
explanation."
George posted and you snipped.
You argue from the standpoint of lack of knowledge of the laws
and practices in the USA regarding the safeguarding of personnel
using electrical devices. And you argue with the experience
and the pictures that show overloaded power strips and extension
cords burned up. Overloaded means used beyond the listed and
labelled rating regardless of the large safety factor included
in that rating. Overheated means the conductor temperature
rise will be higher than it would have when operated within
ratings. The limits/ratings/specifications/whatever term you
wish to use are not based on what you or I think. They are
established by the rules and regs.
Ed
https://media.defense.gov/2016/Jan/22/2001336711/-1/-1/0/160120-F-ZZ999-223.JPG
http://dailyinbox.com/firefighters-blame-overloaded-extension-cords-for-apartment-fire/
George Herold
Jan 2, 2018, 9:27:27 AM1/2/18
to
Thanks for all the responses. (Phil, Ed, others.)
The case in point was at a trade show where we had wired up several
(let's say three, at a guess) power stripes in a row.. all in series.
There was some fault in the electrical distribution, that shut off our
booth power. (Maybe a ground fault?) And the electrician on site blamed
the long daisy chain of power stripes.
George H.
>
>
>
> .... Phil
Phil Hobbs
Jan 2, 2018, 10:10:30 AM1/2/18
to
Seriously, though, as I've said several times before, electrical codes
contain a lot of non-obvious and very expensive wisdom.
Refraining from deliberately shorting the mains is one of the less
non-obvious parts of that. ;)
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
https://hobbs-eo.com
ehsjr
Jan 2, 2018, 11:51:35 PM1/2/18
to
On 1/1/2018 8:26 PM, Phil Allison wrote:
> ehsjr wrote:
>
> ----------------
>
>>
>>>>>>
>>>>>> The mains supply breaker is NOT intended nor designed to protect the
>>>>>> power using equipment. That breaker is there to protect the permanent
>>>>>> wiring from the panel to the outlet to which the power using equipment
>>>>>> is connected.
>>>>>>
>>>>>
>>>>> ** Essentially true, but the next bit is not.
>>>>>
>>>>>
>>>>>> Relying on the mains breaker to make the power using
>>>>>> equipment safe in the event of a fault in that equipment is wrong,
>>>>>> unsafe and stupid everywhere,
>>>>>
>>>>>
>>>>> ** Bollocks.
>>>>>
>>>>>
>>>>>
>>>>>> and is illegal in the USA.
>>>>>
>>>>>
>>>>>
>>>>> ** Really ??
>>>>>
>>>>> So all US appliances have fuses fitted ??
>>>>
>>>>
>>>> No.
>>>
>>>
>>> ** Then at least some of them are dangerous - according to YOU.
>>
>> So you think an appliance must have a fuse must be fitted to make
>> it safe?
>>
>
>
> ** FFS - that is what **YOU** just claimed.
Phil, You either suffer from a serious reading deficiency,
> ehsjr wrote:
>
> ----------------
>
>>
>>>>>>
>>>>>> The mains supply breaker is NOT intended nor designed to protect the
>>>>>> power using equipment. That breaker is there to protect the permanent
>>>>>> wiring from the panel to the outlet to which the power using equipment
>>>>>> is connected.
>>>>>>
>>>>>
>>>>> ** Essentially true, but the next bit is not.
>>>>>
>>>>>
>>>>>> Relying on the mains breaker to make the power using
>>>>>> equipment safe in the event of a fault in that equipment is wrong,
>>>>>> unsafe and stupid everywhere,
>>>>>
>>>>>
>>>>> ** Bollocks.
>>>>>
>>>>>
>>>>>
>>>>>> and is illegal in the USA.
>>>>>
>>>>>
>>>>>
>>>>> ** Really ??
>>>>>
>>>>> So all US appliances have fuses fitted ??
>>>>
>>>>
>>>> No.
>>>
>>>
>>> ** Then at least some of them are dangerous - according to YOU.
>>
>> So you think an appliance must have a fuse must be fitted to make
>> it safe?
>>
>
>
> ** FFS - that is what **YOU** just claimed.
or you're a liar.
Goodbye.
Ed
Don Kuenz
Jan 3, 2018, 12:57:35 PM1/3/18
to
Tim Williams <tiw...@seventransistorlabs.com> wrote:
> "Don Kuenz" <g...@crcomp.net> wrote in message news:2017...@crcomp.net...
>> You might limit the current and trip the mains breaker to cope with the
>> short. That way you simultaneously protect the shorted device and send
>> users a dramatic message that something's wrong.
>
> How does that work?
>> short. That way you simultaneously protect the shorted device and send
>> users a dramatic message that something's wrong.
>
>
> If you have a shunt coil to trip the breaker separately (like a lot of
> UL1077 breakers do, or the guts of a GFCI receptacle), you can open the
> circuit without drawing fault current. Though that still won't act fast
> enough to save a transistor (not without a switching mechanism like I
> described, anyway).
Is it possible to separate the current limit functionality from the
mains breaker trip? Limit the current first and always, sense an over
current state, and then leisurely use a low voltage to trip the mains
breaker a few cycles later?
Thank you,
--
Don Kuenz, KB7RPU
Tim Williams
Jan 3, 2018, 3:29:48 PM1/3/18
to
"Don Kuenz" <g...@crcomp.net> wrote in message news:2018...@crcomp.net...
How would you connect the "low voltage"?
Tim
--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: https://www.seventransistorlabs.com/
> Is it possible to separate the current limit functionality from the
> mains breaker trip? Limit the current first and always, sense an over
> current state, and then leisurely use a low voltage to trip the mains
> breaker a few cycles later?
I mean, a shunt breaker does that, but you mean a regular mains breaker?
> mains breaker trip? Limit the current first and always, sense an over
> current state, and then leisurely use a low voltage to trip the mains
> breaker a few cycles later?
How would you connect the "low voltage"?
Tim
--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: https://www.seventransistorlabs.com/
Don Kuenz
Jan 3, 2018, 3:54:33 PM1/3/18
to
Tim Williams <tiw...@seventransistorlabs.com> wrote:
> "Don Kuenz" <g...@crcomp.net> wrote in message news:2018...@crcomp.net...
>> Is it possible to separate the current limit functionality from the
>> mains breaker trip? Limit the current first and always, sense an over
>> current state, and then leisurely use a low voltage to trip the mains
>> breaker a few cycles later?
>
> I mean, a shunt breaker does that, but you mean a regular mains breaker?
> How would you connect the "low voltage"?
probably cheaper.
Remote Setup, Control, and Monitoring in One Panel
The most advanced self-contained controllable breaker panel
on the market today. The RPC combines all the features you've
come to expect from LynTec panels with new web enabled control
and monitoring capabilities. Based on the G3 PowerlinkTM
hardware platform by Square D, the RPC uses the latest remotely
operated breakers and can control up to 168 circuit breakers
with a single controller. In addition, the RPC's expanded
interface options (DMX, sACN, HTTP, Telnet, RS-232 or BacNET
(optional)) allow users to monitor and control the system from
any remote location.
(excerpt)
https://lyntec.com/remote-control-breaker-panel/
Tim Williams
Jan 3, 2018, 4:05:52 PM1/3/18
to
"Don Kuenz" <g...@crcomp.net> wrote in message news:2018...@crcomp.net...
> RS-232's the old school way and it's probably the most reliable. WiFi's
> probably cheaper.
>
> Remote Setup, Control, and Monitoring in One Panel
<snip>
> probably cheaper.
>
> Remote Setup, Control, and Monitoring in One Panel
Ah, sure -- that'll do, just remember operation might not be guaranteed
(Wifi anyone? :) ), so the self contained breaker action is still needed. A
keep-alive loop might be acceptable to rely on, whether in very basic
hardware like a 4-20mA loop, or in software like a serial watchdog.
It'd be a natural for integration into a panel like that. Though as fuses
and breakers have done just fine over the last century, it seems unlikely
you could justify the cost, except in extraordinary situations (like
aerospace SSPCs).
Don Kuenz
Jan 3, 2018, 5:07:38 PM1/3/18
to
Tim Williams <tiw...@seventransistorlabs.com> wrote:
> "Don Kuenz" <g...@crcomp.net> wrote in message news:2018...@crcomp.net...
>> RS-232's the old school way and it's probably the most reliable. WiFi's
>> probably cheaper.
>>
>> Remote Setup, Control, and Monitoring in One Panel
> <snip>
>
> Ah, sure -- that'll do, just remember operation might not be guaranteed
> (Wifi anyone? :) ), so the self contained breaker action is still needed. A
> keep-alive loop might be acceptable to rely on, whether in very basic
> hardware like a 4-20mA loop, or in software like a serial watchdog.
>
> It'd be a natural for integration into a panel like that. Though as fuses
> and breakers have done just fine over the last century, it seems unlikely
> you could justify the cost, except in extraordinary situations (like
> aerospace SSPCs).
home he VPN connects to his home panel and uses a web browser to keep an
eye on things. He can control any light in the house (and probably
outlets too.)
Granted, it's a more expensive. But it's also relatively common,
if the quantity of companies that service such home panels is any
indication. It looks like Eaton offers a guy that retro-fits into an
existing panel.
Remote Controlled Circuit Breakers
Eaton's Remote Controlled Circuit Breakers offer energy
savings, convenience, and flexibility, all within the
smallest breaker size in the industry. Schedule times for
lighting or building systems to turn on and off. Easy to
upgrade existing panelboards using remote-controllable
breakers. Select from plug-on or bolt-on mountings in
120/240V or 270/480V. For complex systems, see our
complete line of Pow-R-Command Lighting and Load Control.
http://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/CircuitProtection/IndustrialMiniatureCircuitBreakers/RemoteControlledCircuitBreakers/index.htm
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