dodgy mordaunt short speakers

[Terry Given]

Phil Allison wrote:

"Terry Given"

hows this for an outrageous statement: circuit breakers dont limit fault
current, fuses do



** Rates alongside the asinine one that says:


" guns do not kill people.... "

........ Phil

Nah, you just need a nice low supply impedance to see it. With a fault
current of, say, 250,000A the difference between a circuit breaker and a
fuse is extremely obvious (if, of course, you have one hell of a good
CT). I've seen the aftermath of a dead short applied to such a system
whose CB wasnt rated for that level of fault current (and vaporised). oops.

its a bit harder to see in a house, where the fault current is 1,000 -
6,000A (depending on supply impedance, wire size etc). But I'm sure
you've seen many a blown fuse whose rupture current was well below that
(eg every 20mm glass fuse in existence). usually characterised by a
totally destroyed fuse.

have a read of some Gould-Shawmut (bought by Ferraz IIRC) app notes, or
maybe "Applying low-voltage fuses - classes & characteristics", H.W.
Reichenstein, McGraw-Hill, ISBN 07-606577-4


Cheers
Terry

 

[Phil Allison]

"Terry Given"

Phil Allison wrote:
"Terry Given"

hows this for an outrageous statement: circuit breakers dont limit fault
current, fuses do



** Rates alongside the asinine one that says:


" guns do not kill people.... "


Nah, you just need a nice low supply impedance to see it. With a fault
current of, say, 250,000A

** How funking smartarse.

You need to read the title of this NG.

its a bit harder to see in a house, where the fault current is 1,000 -
6,000A

** The ACTUAL short circuit current of a domestic AC outlet is rarely any
more than 250 amps rms.

Go measure the voltage regulation of one with a known load as see how
asinine your numbers are.

(depending on supply impedance, wire size etc). But I'm sure you've seen
many a blown fuse whose rupture current was well below that (eg every 20mm
glass fuse in existence). usually characterised by a totally destroyed
fuse.

** More asinine tripe.

Most glass equipment fuses *can* break 250amps of current and do not need
to break any more since a domestic circuit breaker WILL act instantly at
that current level.





........... Phil

 

[Terry Given]

Phil Allison wrote:

"Terry Given"

Phil Allison wrote:

"Terry Given"


hows this for an outrageous statement: circuit breakers dont limit fault
current, fuses do



** Rates alongside the asinine one that says:


" guns do not kill people.... "


Nah, you just need a nice low supply impedance to see it. With a fault
current of, say, 250,000A



** How funking smartarse.

You need to read the title of this NG.

there are electronics companies in Australasia that make 1MW 3-phase
light dimmers, drives etc.

its a bit harder to see in a house, where the fault current is 1,000 -
6,000A



** The ACTUAL short circuit current of a domestic AC outlet is rarely any
more than 250 amps rms.

depends on how close you are to the switchboard, and the nearest
distribution transformer (which might be right outside your house). New
suburbs tend to have nice low impedance (high efficiency) transformers
(5% cf 10%).

and just how do you measure the RMS short-circuit current? without a
very good CT (wide dynamic range) and a digital scope, it gets pretty
tricky.

then of course it makes a *big* difference when in the line cycle you
apply the short circuit.

peak current is a much more meaningful number when considering fault
currents. If the circuit interrupter works, over what time scale do you
make the RMS measurement?

Go measure the voltage regulation of one with a known load as see how
asinine your numbers are.

which wont tell you much about the short-circuit current at all.

those numbers, BTW, came via the EWRB, which ought to know.

(depending on supply impedance, wire size etc). But I'm sure you've seen
many a blown fuse whose rupture current was well below that (eg every 20mm
glass fuse in existence). usually characterised by a totally destroyed
fuse.



** More asinine tripe.

Most glass equipment fuses *can* break 250amps of current and do not need
to break any more since a domestic circuit breaker WILL act instantly at
that current level.

20mm glass fuses are rated at 125A.

how instantly? ms? us? ns? ps? fs? as?

you cant pull Trevor up for making an "instantly switch" claim for a
polyswitch, then do the same thing yourself for a circuit breaker - at
least not without looking silly

case in point: the CB switch mechanism has a finite, non-zero mass. it
requires infinitely high acceleration to move from one side to another
instantaneously. Physics 101

.......... Phil

Cheers
Terry

 

[Trevor Wilson]

"Terry Given" <my_name@ieee.org> wrote in message
news:MALQe.6942$iM2.701408@news.xtra.co.nz...

Trevor Wilson wrote:
"Terry Given" <my_name@ieee.org> wrote in message
news:CPCQe.6885$iM2.684414@news.xtra.co.nz...

Trevor Wilson wrote:

"Terry Given" <my_name@ieee.org> wrote in message
news:2%AQe.6851$iM2.680368@news.xtra.co.nz...


Phil Allison wrote:


"Terry Given"



Its the crossover network (MSP1B), which has PTC thermistors in
series with the mid/bass and tweeters. They both have a (measured)
PTC characteristic, bass/mid measures about 0.3 Ohms cold, the
tweeter about 51 Ohms - which seems pretty high to me.




** The PTC is faulty.

Go look at the published specs - even 0.5 amp rated PTCs have low
cold ohmages.

............ Phil

Hi Phil,

spot on. The tweeter ptc is 8mm diameter, bass/mid 13mm. I figured 51R
cold must be buggered, but was unsure about 0R3. A simple hand-wavey
calc shows its probably too high (the speakers are 8R), and a
measurement (with earmuffs, scope & freeze spray) confirms its the
culprit.

whats the tweeter current rating likely to be? I have been told the
speakers are rated at 100W, but cant track down any real data.

I can get a suitable small PTC from Farnell, but the best they have is
0R45 at 25C for the big PTC. My guess is I want 0R1. Any suggestions?


**Polyswitches can be purchased from a number of sources. WES Components
and Jaycar are very cheap and they stock a wide range. In general, you
would choose an 075 (or thereabouts) for the tweeter and a 1.15 for the
bass. If they measure almost S/C when cold, then they're probably fine.

Hi Trevor,

075 to replace the 070, and a 160 to replace the 135. Jaycar it is, Kev
will pick them up 2morrow. thanks for your help.


**Better to err on the low side. Particularly for the bass driver
Polyswitch.

OK, will do.



I'm just being pedantic here, but how S/C is S/C?


**With average speakers, 0.3 Ohms is adequate. The advantage of a
Polyswitch is that it remains at the low resistance, then 'switches' to
high resistance. Fuses do not. A fuse will increase it's resistance with
increases in current.

thats not how these behaved, I measured the resistance while heating it
with my Hakko 850B hot air rework station, a nice gradual function of
temperature. Which is why I thought it was a PTC. But that perhaps means
nothing, as the device is (I think) faulty.

When the new parts arrive, I'll take some comparitive measurements,
including temperature, and post the results.

**I just tested a few. They do not 'switch'. They do, indeed, limit current,
depending on the temperature of the device. Naturally, since the fault
current causes heating, the internal resistance rises, which, in turn,
causes more heating and more temperature rises. Once the rated current is
reached, it shuts off power rapidly enough to protect devices which can
tolerate a modest overload (ie: Loudspeaker drivers).


--
Trevor Wilson
www.rageaudio.com.au

 

[Phil Allison]

"Terry Given = grade A, Kiwi, PITA, fucking TROLL

** How funking smartarse.

You need to read the title of this NG.


there are electronics companies in Australasia that make 1MW 3-phase light
dimmers, drives etc.

** So what - smartarse ?

its a bit harder to see in a house, where the fault current is 1,000 -
6,000A

** The ACTUAL short circuit current of a domestic AC outlet is rarely
any more than 250 amps rms.

depends on how close you are to the switchboard,

** Can you read - smartarse ??

See the word "rarely" ?????

and just how do you measure the RMS short-circuit current?

** I just told you.

You use ohms law.

Go measure the voltage regulation of one with a known load as see how
asinine your numbers are.


which wont tell you much about the short-circuit current at all.

** So you have no faith in ohms' law now - smartarse ?

Poor Georg Ohm will be very upset.

those numbers, BTW, came via the EWRB, which ought to know.

** Go measure a domestic power outlet's voltage regulation.

From that you learn the internal resistance in ohms.

Divide that number into 240 to find the short circuit current in AC amps
rms.

Otherwise, go get fucked.

** More asinine tripe.

Most glass equipment fuses *can* break 250amps of current and do not
need to break any more since a domestic circuit breaker WILL act
instantly at that current level.

20mm glass fuses are rated at 125A.

how instantly? ms? us? ns? ps? fs? as?

** We have a bipolar disorder sufferer here - in manic mode.

you cant pull Trevor up for making an "instantly switch" claim for a
polyswitch,

** No such thing ever happened and the quotation is a fake.


If you do not understand what the words "act instantly" mean in relation
to an AC breaker, then god help you Terry.




............. Phil

 

[Terry Given]

Phil Allison wrote:

"Terry Given = grade A, Kiwi, PITA, fucking TROLL


** How funking smartarse.

You need to read the title of this NG.


there are electronics companies in Australasia that make 1MW 3-phase light
dimmers, drives etc.



** So what - smartarse ?

so its still electronics, albeit bigger than the little stuff you play
with. Hence the relevance.

its a bit harder to see in a house, where the fault current is 1,000 -
6,000A

** The ACTUAL short circuit current of a domestic AC outlet is rarely
any more than 250 amps rms.

depends on how close you are to the switchboard,



** Can you read - smartarse ??

See the word "rarely" ?????

ah, the joys of weasel-words.

on what basis do you make that claim though? measuring Zsupply at 1Ohm?

and just how do you measure the RMS short-circuit current?



** I just told you.

You use ohms law.



Go measure the voltage regulation of one with a known load as see how
asinine your numbers are.


which wont tell you much about the short-circuit current at all.



** So you have no faith in ohms' law now - smartarse ?

Poor Georg Ohm will be very upset.

V = IZ pretty much always works. V=IR less so.

those numbers, BTW, came via the EWRB, which ought to know.



** Go measure a domestic power outlet's voltage regulation.

From that you learn the internal resistance in ohms.

Divide that number into 240 to find the short circuit current in AC amps
rms.

Otherwise, go get fucked.

it doesnt take into account transformer saturation, or skin effect, or
inductance, (these two may be very significant when rapidly applying a
short at the peak of line voltage) or any nearby rotating loads - short
the grid, and all motors become generators. And there are probably a few
other things I cant think of OTTOMH.


sometime this arvo' I'll measure Isc in my old house. By applying a
short circuit and measuring it.

** More asinine tripe.

Most glass equipment fuses *can* break 250amps of current and do not
need to break any more since a domestic circuit breaker WILL act
instantly at that current level.

20mm glass fuses are rated at 125A.

how instantly? ms? us? ns? ps? fs? as?



** We have a bipolar disorder sufferer here - in manic mode.

OK, I was being pedantic

you cant pull Trevor up for making an "instantly switch" claim for a
polyswitch,



** No such thing ever happened and the quotation is a fake.

OK, he didnt say "instantly"

but it does "switch", albeit slowly.

If you do not understand what the words "act instantly" mean in relation
to an AC breaker, then god help you Terry.

............ Phil

god doesnt help anyone. Why would she help me, I'm an atheist.

Cheers
Terry

 

[Phil Allison]

"Terry Given"

so its still electronics,

** No it is not.

it doesnt take into account transformer saturation, or skin effect, or
inductance,

** Madness - additional effects can only* reduce* the amp flow under
short circuit.

** We have a bipolar disorder sufferer here - in manic mode.

OK, I was being pedantic

** No - "manic" is the term for your illness - Terry.

** No such thing ever happened and the quotation is a fake.

OK, he didnt say "instantly"

** The term is "manic" - Terry - go look it up.

If you do not understand what the words "act instantly" mean in
relation to an AC breaker, then god help you Terry.


god doesnt help anyone.

** Then you are totally stuffed.

Why would she help me, I'm an atheist.

** You're a desperate lunatic.



............ Phil

 

[Terry Given]

Phil Allison wrote:

"Terry Given"


so its still electronics,


** No it is not.

OK, how big does an IGBT have to be before it stops beng electronics?

I've used 100mA SCRs, and 2,000A SCRs. Is the former electronics, if the
latter is not?

mighty peculiar definition.

it doesnt take into account transformer saturation, or skin effect, or
inductance,



** Madness - additional effects can only* reduce* the amp flow under
short circuit.

Really? I note you snipped out rotating loads on the same network. Oops,
every power systems engineer in the world is wrong.

** We have a bipolar disorder sufferer here - in manic mode.

OK, I was being pedantic



** No - "manic" is the term for your illness - Terry.




** No such thing ever happened and the quotation is a fake.

OK, he didnt say "instantly"



** The term is "manic" - Terry - go look it up.



If you do not understand what the words "act instantly" mean in
relation to an AC breaker, then god help you Terry.


god doesnt help anyone.



** Then you are totally stuffed.



Why would she help me, I'm an atheist.



** You're a desperate lunatic.

better than being pathetic enough to require a god.

........... Phil

 

[Phil Allison]

"Terry Given"

Phil Allison wrote:

so its still electronics,


** No it is not.

OK, how big does an IGBT .....

** Take you meds - Terry.

it doesnt take into account transformer saturation, or skin effect, or
inductance,


** Madness - additional effects can only* reduce* the amp flow under
short circuit.

Really?

** Take you meds - Terry.

I note you snipped out rotating loads on the same network.

** So you missed the word domestic as well - fuckhead ?

Take you meds - Terry.

You are completely fucked in the head.

Bugger off.





.......... Phil

 

text removed for the hell of it

......... Phil

Morning,

It would seem that Terry is quite right with what he says - the short
circuit current in a house or unit could reach as high as 6 or even
10kA. In a block of units with a pole or package sub close by this is
quite likely.

If the fault current at the switchboard is as low as .25kA then fault
loop impedance could become a problem and circuit breakers may not
operate fast enough on faults.

You can get current limiting circuit breakers which apparently do
operate within half a cycle, though Ive not measured or seen this
actually checked out before.

The converter stations for HVDC powerlines have some pretty impressive
electronics in them, operating at 100's of MV and kV. I suspect they
don't use Printed Circuit Boards for those Thyristors though

Cheers
Crim

 

[Phil Allison]

<j.l@octa4.net.au>

It would seem that Terry is quite right with what he says - the short
circuit current in a house or unit could reach as high as 6 or even
10kA.

** Shame the demented dude never said that.

Best of all he never put any money on it, nor produced any proof.

In a block of units with a pole or package sub close by this is
quite likely.

** Self opinion.

If the fault current at the switchboard is as low as .25kA

** Straw man.

You can get current limiting circuit breakers which apparently do
operate within half a cycle, though Ive not measured or seen this
actually checked out before.

** I have - so you suck at it.

The converter stations for HVDC powerlines have some pretty impressive
electronics in them,

** Err - so does the fucking Space Shuttle.

operating at 100's of MV and kV. I suspect they
don't use Printed Circuit Boards for those Thyristors though

** Nah - most PCB tracks crap out at 10 amps.


Ohm's law rules - Ok ??




.......... Phil

 

[Terry Given]

j.l@octa4.net.au wrote:

text removed for the hell of it





......... Phil


Morning,

It would seem that Terry is quite right with what he says - the short
circuit current in a house or unit could reach as high as 6 or even
10kA. In a block of units with a pole or package sub close by this is
quite likely.

yep. OTOH if you are at the end of a very long wire, fault current will
be a lot lower (but voltage regulation will be seriously bad). Ah, the
joys of living out in the wops.

If the fault current at the switchboard is as low as .25kA then fault
loop impedance could become a problem and circuit breakers may not
operate fast enough on faults.

yep. I guess thats why we have an M.E.N. distribution system (OK, I
lied, its not a guess

You can get current limiting circuit breakers which apparently do
operate within half a cycle, though Ive not measured or seen this
actually checked out before.

what mechanism do they use for limiting current? fuses do it by
absorbing energy.

The converter stations for HVDC powerlines have some pretty impressive
electronics in them, operating at 100's of MV and kV. I suspect they
don't use Printed Circuit Boards for those Thyristors though

I've seen the DC link at Haywards Hill, NZ. very impressive. Many, many
thyristors in series - when one fails, it fails short-cct, so they have
N+shitloads redundancy, allowing the system to be maintained when the
operator chooses (as opposed to when the dodgy thyristor chooses).

Cheers
Crim

Cheers
Terry

 

[Terry Given]

Phil Allison wrote:

j.l@octa4.net.au

It would seem that Terry is quite right with what he says - the short
circuit current in a house or unit could reach as high as 6 or even
10kA.



** Shame the demented dude never said that.

Best of all he never put any money on it, nor produced any proof.



In a block of units with a pole or package sub close by this is
quite likely.



** Self opinion.



If the fault current at the switchboard is as low as .25kA



** Straw man.



You can get current limiting circuit breakers which apparently do
operate within half a cycle, though Ive not measured or seen this
actually checked out before.



** I have - so you suck at it.



The converter stations for HVDC powerlines have some pretty impressive
electronics in them,



** Err - so does the fucking Space Shuttle.



operating at 100's of MV and kV. I suspect they
don't use Printed Circuit Boards for those Thyristors though



** Nah - most PCB tracks crap out at 10 amps.

only if you dont know what you are doing. Would you like me to post a
couple of pics - a 100kW drive power electronics stack done with a
single PCB, a 2500W 50mm diameter power transformer (driven by smps
running from 16Vdc) that uses a PCB for some of the windings, a 55W 2.8V
smps done one a single PCB, with planar xfmr & inductor (do the maths...)

You are often right, Phil, just not this time.

Next you will be telling me 10Oz Cu PCBs dont exist, or that
transformers cannot be wound using PCBs (check out NZ patent NZ299391),
or that IGBTs arent electronics - oops, too late, you've already made
that claim.

Ohm's law rules - Ok ??

not so useful for distributed circuits though.

......... Phil

Cheers
Terry

 

[Terry Given]

Phil Allison wrote:

"Terry Given"

Phil Allison wrote:

so its still electronics,


** No it is not.

OK, how big does an IGBT .....

Oh, so you *CANNOT* answer that question. No doubt because you have
realised that you are wrong. Cheer up, we all make mistakes. Suck back
the invective, you might learn something.

ever heard of the term "Power Electronics"

silly man.

** Take you meds - Terry.



it doesnt take into account transformer saturation, or skin effect, or
inductance,


** Madness - additional effects can only* reduce* the amp flow under
short circuit.

Really?



** Take you meds - Terry.



I note you snipped out rotating loads on the same network.



** So you missed the word domestic as well - fuckhead ?

ever seen a house next door to a factory?

Take you meds - Terry.

You are completely fucked in the head.

Bugger off.





......... Phil

 

[Phil Allison]

"Terry Given"

** Nah - most PCB tracks crap out at 10 amps.

only if you dont know what you are doing.

** Still canot see important words in one sentence.

You are often right, Phil, just not this time.

** Take yor meds - Terry !

You have totally lost it.




............ Phil

 

Terry Given wrote:

j.l@octa4.net.au wrote:
text removed for the hell of it





......... Phil


Morning,

It would seem that Terry is quite right with what he says - the short
circuit current in a house or unit could reach as high as 6 or even
10kA. In a block of units with a pole or package sub close by this is
quite likely.

yep. OTOH if you are at the end of a very long wire, fault current will
be a lot lower (but voltage regulation will be seriously bad). Ah, the
joys of living out in the wops.


If the fault current at the switchboard is as low as .25kA then fault
loop impedance could become a problem and circuit breakers may not
operate fast enough on faults.

yep. I guess thats why we have an M.E.N. distribution system (OK, I
lied, its not a guess

Yes true, direct earthing wouldn't work too well. Earth fault loop

impedance still applies and can still be a problem though. Its also
seems to be rarely checked by anyone. A low fault current at the point
of supply will make this more difficult to comply with. Its in AS3000
but in a suburban situation its rarely a problem.

You can get current limiting circuit breakers which apparently do
operate within half a cycle, though Ive not measured or seen this
actually checked out before.

what mechanism do they use for limiting current? fuses do it by
absorbing energy.

I think the idea is they disconnect the load in a short enough time
that the current never rises above a certain level. ACBs have arch
chutes and various patented methods of extinguishing arcs quickly. If
the ionised air is removed the current flow is stopped faster.

HV breakers use oil SF6 or vacuum interrupters to do this, I haven't
seen LV breakers use vacuum or SF6 but maybe they exist. Oil breakers
have a nasty habit of exploding so they try not to use them in new
installations.

The converter stations for HVDC powerlines have some pretty impressive
electronics in them, operating at 100's of MV and kV. I suspect they
don't use Printed Circuit Boards for those Thyristors though

I've seen the DC link at Haywards Hill, NZ. very impressive. Many, many
thyristors in series - when one fails, it fails short-cct, so they have
N+shitloads redundancy, allowing the system to be maintained when the
operator chooses (as opposed to when the dodgy thyristor chooses).

Biggest drives Ive seen inside of are only a few hundred kW at low

voltage, only seen pictures and video of these masstive converters.

Are large high current PCB's still etched or do they machine the tracks
instead? Hybrid cars might bring about some interesting developments in
this area....... Can imagine an entire drive kind of becoming a single
chip....

Cheers

Cheers
Crim

Cheers
Terry

 

[Terry Given]

j.l@octa4.net.au wrote:

Terry Given wrote:

j.l@octa4.net.au wrote:

text removed for the hell of it





......... Phil


Morning,

It would seem that Terry is quite right with what he says - the short
circuit current in a house or unit could reach as high as 6 or even
10kA. In a block of units with a pole or package sub close by this is
quite likely.

yep. OTOH if you are at the end of a very long wire, fault current will
be a lot lower (but voltage regulation will be seriously bad). Ah, the
joys of living out in the wops.


If the fault current at the switchboard is as low as .25kA then fault
loop impedance could become a problem and circuit breakers may not
operate fast enough on faults.

yep. I guess thats why we have an M.E.N. distribution system (OK, I
lied, its not a guess


Yes true, direct earthing wouldn't work too well. Earth fault loop
impedance still applies and can still be a problem though. Its also
seems to be rarely checked by anyone. A low fault current at the point
of supply will make this more difficult to comply with. Its in AS3000
but in a suburban situation its rarely a problem.


You can get current limiting circuit breakers which apparently do
operate within half a cycle, though Ive not measured or seen this
actually checked out before.

what mechanism do they use for limiting current? fuses do it by
absorbing energy.



I think the idea is they disconnect the load in a short enough time
that the current never rises above a certain level. ACBs have arch
chutes and various patented methods of extinguishing arcs quickly. If
the ionised air is removed the current flow is stopped faster.

HV breakers use oil SF6 or vacuum interrupters to do this, I haven't
seen LV breakers use vacuum or SF6 but maybe they exist. Oil breakers
have a nasty habit of exploding so they try not to use them in new
installations.

that'd do it, but it would need to be real fast - much less than 5ms.

The converter stations for HVDC powerlines have some pretty impressive
electronics in them, operating at 100's of MV and kV. I suspect they
don't use Printed Circuit Boards for those Thyristors though

I've seen the DC link at Haywards Hill, NZ. very impressive. Many, many
thyristors in series - when one fails, it fails short-cct, so they have
N+shitloads redundancy, allowing the system to be maintained when the
operator chooses (as opposed to when the dodgy thyristor chooses).


Biggest drives Ive seen inside of are only a few hundred kW at low
voltage, only seen pictures and video of these masstive converters.

I blew up a couple of 1MW drives at Beenup a few years back. Man, did
they go bang.

Are large high current PCB's still etched or do they machine the tracks
instead? Hybrid cars might bring about some interesting developments in
this area....... Can imagine an entire drive kind of becoming a single
chip....

we used 1.6mm Al plates, separated by a 1mm nomex insulator, for the DC
bus. Caps & IGBTs bolt directly to it, with dunks & holes to get levels
& creepage/clearance right. The 660A drives used Cu not Al. the 1MW
drives were 3 660A drives directly paralleled (at the IGBT gate drive
level). Fun stuff.

Cheers


Cheers
Crim

Cheers
Terry