Driver to drive?

krw wrote:
On Sun, 08 Nov 2009 22:04:06 -0500, RFI-EMI-GUY
Rhyolite@NETTALLY.COM> wrote:

krw wrote:
On Thu, 29 Oct 2009 11:09:20 +0000, Raveninghorde
raveninghorde@invalid> wrote:

One of my chaps is off to do his PhD, which means he will know a lot
about nothing.

He asked me the other day if reversing the 24V AC power supply to a
board had caused damage to an elctrolytic capacitor. I don't think
you have to know the circuit to answer the question.

Talk about not understanding what he knows.

Many moons ago, when GE still made small appliances, they had a
troubleshooting tip for a toaster suggesting that if it didn't work
the user should try reversing the plug. Kinda cute, actually.


They might have put that bit in because its less insulting than to say
"PLUG THE DAMN THING IN!"

Exactly; kinda cute. ;-)
Click to expand...

Except for the fact tat GE never made those appliances. They were
made by Black & Decker for GE.


--
The movie 'Deliverance' isn't a documentary!
 
On Mon, 09 Nov 2009 09:15:30 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

krw wrote:

On Sun, 08 Nov 2009 22:04:06 -0500, RFI-EMI-GUY
Rhyolite@NETTALLY.COM> wrote:

krw wrote:
On Thu, 29 Oct 2009 11:09:20 +0000, Raveninghorde
raveninghorde@invalid> wrote:

One of my chaps is off to do his PhD, which means he will know a lot
about nothing.

He asked me the other day if reversing the 24V AC power supply to a
board had caused damage to an elctrolytic capacitor. I don't think
you have to know the circuit to answer the question.

Talk about not understanding what he knows.

Many moons ago, when GE still made small appliances, they had a
troubleshooting tip for a toaster suggesting that if it didn't work
the user should try reversing the plug. Kinda cute, actually.


They might have put that bit in because its less insulting than to say
"PLUG THE DAMN THING IN!"

Exactly; kinda cute. ;-)


Except for the fact tat GE never made those appliances. They were
made by Black & Decker for GE.
Click to expand...
Hmmmm? IIRC GE (appliances) and Black & Decker were separate entities
until B & D bought the GE Small Appliance Division , retained the name
for quite some time, then started labeling them as B & D ??

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Obama says, "I AM NOT a cry baby, Fox REALLY IS out to get me!"
 
Jim Thompson wrote:
On Mon, 09 Nov 2009 09:15:30 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


krw wrote:

On Sun, 08 Nov 2009 22:04:06 -0500, RFI-EMI-GUY
Rhyolite@NETTALLY.COM> wrote:

krw wrote:
On Thu, 29 Oct 2009 11:09:20 +0000, Raveninghorde
raveninghorde@invalid> wrote:

One of my chaps is off to do his PhD, which means he will know a lot
about nothing.

He asked me the other day if reversing the 24V AC power supply to a
board had caused damage to an elctrolytic capacitor. I don't think
you have to know the circuit to answer the question.

Talk about not understanding what he knows.

Many moons ago, when GE still made small appliances, they had a
troubleshooting tip for a toaster suggesting that if it didn't work
the user should try reversing the plug. Kinda cute, actually.


They might have put that bit in because its less insulting than to say
"PLUG THE DAMN THING IN!"

Exactly; kinda cute. ;-)


Except for the fact tat GE never made those appliances. They were
made by Black & Decker for GE.

Hmmmm? IIRC GE (appliances) and Black & Decker were separate entities
until B & D bought the GE Small Appliance Division , retained the name
for quite some time, then started labeling them as B & D ??
Click to expand...

I used to buy tools from a B&D factory outlet store. They always had
piles of refurbished GE coffee makers and toasters, along with other GE
odds & ends. This was years before they put their own name on them.
When I asked about them, I was told that they had made them for GE for
decades. That was over 20 years ago. They told me that GE made large
appliances, but not any small appliances.


--
The movie 'Deliverance' isn't a documentary!
 
On Mon, 09 Nov 2009 09:15:30 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

krw wrote:

On Sun, 08 Nov 2009 22:04:06 -0500, RFI-EMI-GUY
Rhyolite@NETTALLY.COM> wrote:

krw wrote:
On Thu, 29 Oct 2009 11:09:20 +0000, Raveninghorde
raveninghorde@invalid> wrote:

One of my chaps is off to do his PhD, which means he will know a lot
about nothing.

He asked me the other day if reversing the 24V AC power supply to a
board had caused damage to an elctrolytic capacitor. I don't think
you have to know the circuit to answer the question.

Talk about not understanding what he knows.

Many moons ago, when GE still made small appliances, they had a
troubleshooting tip for a toaster suggesting that if it didn't work
the user should try reversing the plug. Kinda cute, actually.


They might have put that bit in because its less insulting than to say
"PLUG THE DAMN THING IN!"

Exactly; kinda cute. ;-)


Except for the fact tat GE never made those appliances. They were
made by Black & Decker for GE.
Click to expand...
That's simply not true. B&D bought GE small appliances, along with
the name, some time back (late '60s, IIRC) but GE *did* make and
market their own small appliances.
 
krw wrote:
On Mon, 09 Nov 2009 09:15:30 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


krw wrote:

On Sun, 08 Nov 2009 22:04:06 -0500, RFI-EMI-GUY
Rhyolite@NETTALLY.COM> wrote:

krw wrote:
On Thu, 29 Oct 2009 11:09:20 +0000, Raveninghorde
raveninghorde@invalid> wrote:

One of my chaps is off to do his PhD, which means he will know a lot
about nothing.

He asked me the other day if reversing the 24V AC power supply to a
board had caused damage to an elctrolytic capacitor. I don't think
you have to know the circuit to answer the question.

Talk about not understanding what he knows.

Many moons ago, when GE still made small appliances, they had a
troubleshooting tip for a toaster suggesting that if it didn't work
the user should try reversing the plug. Kinda cute, actually.


They might have put that bit in because its less insulting than to say
"PLUG THE DAMN THING IN!"

Exactly; kinda cute. ;-)


Except for the fact tat GE never made those appliances. They were
made by Black & Decker for GE.

That's simply not true. B&D bought GE small appliances, along with
the name, some time back (late '60s, IIRC) but GE *did* make and
market their own small appliances.
Click to expand...

Then who is making small GE appliances these days? They just ran a
GE small appliance ad on TV.


--
The movie 'Deliverance' isn't a documentary!
 
On Mon, 09 Nov 2009 22:27:04 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

krw wrote:

On Mon, 09 Nov 2009 09:15:30 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


krw wrote:

On Sun, 08 Nov 2009 22:04:06 -0500, RFI-EMI-GUY
Rhyolite@NETTALLY.COM> wrote:

krw wrote:
On Thu, 29 Oct 2009 11:09:20 +0000, Raveninghorde
raveninghorde@invalid> wrote:

One of my chaps is off to do his PhD, which means he will know a lot
about nothing.

He asked me the other day if reversing the 24V AC power supply to a
board had caused damage to an elctrolytic capacitor. I don't think
you have to know the circuit to answer the question.

Talk about not understanding what he knows.

Many moons ago, when GE still made small appliances, they had a
troubleshooting tip for a toaster suggesting that if it didn't work
the user should try reversing the plug. Kinda cute, actually.


They might have put that bit in because its less insulting than to say
"PLUG THE DAMN THING IN!"

Exactly; kinda cute. ;-)


Except for the fact tat GE never made those appliances. They were
made by Black & Decker for GE.

That's simply not true. B&D bought GE small appliances, along with
the name, some time back (late '60s, IIRC) but GE *did* make and
market their own small appliances.


Then who is making small GE appliances these days? They just ran a
GE small appliance ad on TV.
Click to expand...
Last I knew, B&D (see: "along with the name", above). BTW, I believe
GE still make major appliances.
 
On Oct 29, 6:37 pm, dpl...@radagast.org (Dave Platt) wrote:
In article <hcd9hm$qb...@localhost.localdomain>,
Ian Bell  <ruffreco...@yahoo.com> wrote:

Is it me or was it only 'in the old days' that people went into
electronics (.i.e. got educated in it at college level) because they
were already hooked on it and had built a bunch of stuff? A friend and I
were selling crystal radios at primary school before we were eleven
years old. By the time I was 18 and went to university I had read every
electronics book in the city library, passed the Radio Amateurs Exam,
and built dozens of bits of kit. Don't kids do that any more?

Some do, but my impression is that it's much less common than in the
past.

Years ago, the only way for kids to gain access to electronics (and
the corresponding "wow factor") was to do as you've said - jump in and
start experimenting and building stuff.  My own introduction was a
crystal-radio kit given to me as a 10th-birthday present by my
grandfather.  Highly addictive.

These days, kids can stroll into a mall store, drop a week's allowance
on the counter, and buy an electronic gizmo that does far more than
anything they could build themselves (and is probably designed for a
saturation-level bells-and-whistles-and-WOW! neatness factor).

The thrill is gone, I'm afraid.  Or, rather, access to the thrill is
much more widely distributed.  Individual learning and experimentation
isn't the only path to playing with high-tech goodies available to
kids any more.

It's a shame, in a way.

It's not just electronics, either... whole aspects of self-directed
learning and experience seem to have atrophied, perhaps for similar
reasons.  A few months ago I asked a school-teacher I'd just met, how
many of her middle-school students read books independently, for
pleasure.

Her response was to hold up thumb and forefinger, forming a "zero".

She then amended her response, saying "Well, there may be one or two."

--
Dave Platt <dpl...@radagast.org>                                   AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!
Click to expand...
The talented ones do software rather than hardware these days.

Ever hear of companies named Microsoft and Google?

TMT
 
On Nov 1, 8:23 am, ChrisQ <m...@devnull.com> wrote:
Bill Sloman wrote:
Jim-out-of-touch-with-reality-Thompson strikes again. I'm actually a
useful odd-jobs man, and do carpentry, plumbing, and the odd bit of
household wiring. I am left-handed, and do understand differential
screws.

You know I don't take sides :), but I agree, multidisciplinary skills
are very usefull and are in decline as everything gets more specialised.
I think it's partly a generational thing as the immediate post ww2
generation had to make do and mend everything. I still do all the
electrical, radio, tv, carpentry and even building work around the house
and that's besides interests in mechanical engineering and a core skill
set of software engineering coming from an electronics background. It's
surprising how usefull it can be in all sorts of ways.

I don't think you can generalise about phd's either. I've met some who
knew nothing outside their specialist field, head in the clouds and
others who were some of the most switched on people i've ever met. Some
of the EE graduates i've worked with in the past could hardly solder two
wires together and had no interest at all in the job outside work. I
find that depressing, as to be really good at anything, you need to have
a passion for the subject and have a very inquisitive mind. The lack of
scientific curiosity and the general dumbing down of everything will be
the undoing of our civilisation. Nearly everything we come into contact
with on a daily basis depends on science or engineering in some way...

Regards,

Chris
Click to expand...
Well said.

I agree.

TMT
 
On Nov 1, 6:54 pm, Charlie E. <edmond...@ieee.org> wrote:
On Sat, 31 Oct 2009 18:27:34 -0500, krw <k...@att.bizzzzzzzzzzz> wrote:
On Sat, 31 Oct 2009 11:23:05 -0800, John Larkin
jjSNIPlar...@highTHISlandtechnology.com> wrote:
So skip the basics and take advanced courses.

Advanced courses?  What advanced courses?

Well, twenty years ago (Wow! how time flies!) when I decided to go
back to school and get my EE degree, I learned a lot of interesting
lessons.  

While I had been a hobbiest since I was a kid, my bachelors degree was
in psychology.  I know that I didn't know a lot of the math and such,
so went back to get a second bachelors in EE.  I moved from California
to New Mexico just to get into a program, and in my first class
learned my first lesson.

You don't need a bachelors in EE to get a Masters in EE.

Because of that lesson, I inquired back in California, and a year
later started at UC Santa Barbara in the Masters program.

I started taking a lot of the basic circuits and control theory
classes, and found myself on academic probation.  In the masters
program, you need to keep a 3.0 gpa, but in those basic theory
classes, they graded to a 2.0 average.  These were also the 'weed'
classes, where they TRIED to get students to fail, by heaping so much
make work on them that they would be overwhelmed.  My problem - I
didn't do all the homework and make it look spiffy and nice, I just
did what I needed to learn the subject.  I had A's  and B's on all the
tests.  In my second semester, the T.A.s taught me the second lesson:

When there is a bachelor level course, and a master's level course,
take the Master's level course.

In the BS course, they go into excruciating detail on the basics, as
well as heaping loads of meaningless homework on the poor students. In
the Master's class, they mention the important aspects of the basics
in teh first couple of weeks, and then get right to business. The
Master's courses also tended to be more real world, with actual
applications and circuits.  If you could keep up, they were a lot more
fun.  they also graded to a B curve, not a C curve!

The final lesson was, choose your professors carefully.  I took
classes from many professors, but learned after almost flunking the
second class in a row from one professor, that we were not on the same
page.  I had the same material from two different professors, and from
him it always sounded like greek, while I grok'd the material
instantly from the other.  Sometimes, the learning chemistry is just
not there.

Charlie
Click to expand...
Again a good discussion and I agree.

TMT
 
krw wrote:
On Mon, 09 Nov 2009 22:27:04 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


krw wrote:

On Mon, 09 Nov 2009 09:15:30 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


krw wrote:

On Sun, 08 Nov 2009 22:04:06 -0500, RFI-EMI-GUY
Rhyolite@NETTALLY.COM> wrote:

krw wrote:
On Thu, 29 Oct 2009 11:09:20 +0000, Raveninghorde
raveninghorde@invalid> wrote:

One of my chaps is off to do his PhD, which means he will know a lot
about nothing.

He asked me the other day if reversing the 24V AC power supply to a
board had caused damage to an elctrolytic capacitor. I don't think
you have to know the circuit to answer the question.

Talk about not understanding what he knows.

Many moons ago, when GE still made small appliances, they had a
troubleshooting tip for a toaster suggesting that if it didn't work
the user should try reversing the plug. Kinda cute, actually.


They might have put that bit in because its less insulting than to say
"PLUG THE DAMN THING IN!"

Exactly; kinda cute. ;-)


Except for the fact tat GE never made those appliances. They were
made by Black & Decker for GE.

That's simply not true. B&D bought GE small appliances, along with
the name, some time back (late '60s, IIRC) but GE *did* make and
market their own small appliances.


Then who is making small GE appliances these days? They just ran a
GE small appliance ad on TV.

Last I knew, B&D (see: "along with the name", above). BTW, I believe
GE still make major appliances.
Click to expand...

I see B&D small appliances in stores, and I have a crappy GE washer &
dryer in my laundry room. They were bought new and used less than two
months by my dad & stepmom before being replaced with a new pair from
Sears. I'm still using my 20+ year old sears washer & dryer and will,
until they aren't worth repairing.


--
The movie 'Deliverance' isn't a documentary!
 
Phil Hobbs Inscribed thus:

DaveC wrote:
I would go with the 87 as it seems to be better in just about every
way looking at the specs. It has better accuracy and resolution in
almost all categories.

Accuracy and resolution are great, but for me in my work these really
come in second to features (the low-Z and low-pass features,
specifically).

If it were not for the lack of a low-Z feature I'd buy the 87 in a
second.

But I need to determine if -- as pertains specifically to VFD voltage
measurement -- the 117 is deficient (ie, does noise really cripple
voltage measurement, and how often is this a problem when working in
VFDs) in this respect.

Thanks.


Owning an 87 is the mark of a True Hardware Guy (tm).

Cheers

Phil Hobbs
Click to expand...
I have a AVO 8 MkII what does that say about me. :)

--
Best Regards:
Baron.
 
baron wrote:
Phil Hobbs Inscribed thus:

DaveC wrote:
I would go with the 87 as it seems to be better in just about every
way looking at the specs. It has better accuracy and resolution in
almost all categories.
Accuracy and resolution are great, but for me in my work these really
come in second to features (the low-Z and low-pass features,
specifically).

If it were not for the lack of a low-Z feature I'd buy the 87 in a
second.

But I need to determine if -- as pertains specifically to VFD voltage
measurement -- the 117 is deficient (ie, does noise really cripple
voltage measurement, and how often is this a problem when working in
VFDs) in this respect.

Thanks.

Owning an 87 is the mark of a True Hardware Guy (tm).

Cheers

Phil Hobbs

I have a AVO 8 MkII what does that say about me. :)
Click to expand...
I love Avometers.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
 
Sparky wrote:
This cap was removed from a 70's-80's German industrial machine:

http://i37.tinypic.com/10psxg3.jpg

It has no polarity markings. One terminal is common with the metal case. Is
this always an indication of the (-) terminal?

The base has molded terminal locations numbered 1-4, two of which are empty:

http://i36.tinypic.com/e6x542.jpg

Markings on the side are:

B41111-B7108-T
1000uF 40V-
GERMANY
GPF DIN 41332 06.78

I find a few references to a Siemens part that is similar:

http://www.screenghost.com/shop/show.asp?ID=74#

but no datasheet can I find. Can someone more resourceful than I find one?

I cut open one of these caps. It is paper & foil (or so it seems) spiral wrap
construction. Can polarity be determined by internal construction? Is the
center terminal always one pole (ie, always +)?

Thanks.
Click to expand...
If you *really* can't identify polarity from the part, trace the circuit
back to the rectifier, another cap or dc input to the board. Or, solder
a non polarised cap of a few uF to the board, power up and check with a
meter. The fact that it's lower uF than the electrolytic is unlikely to
damage anything...

Regards,

Chris
 
Rich Grise wrote:
On Thu, 12 Nov 2009 19:17:43 +1100, Sylvia Else wrote:
Phil Allison wrote:
The markings are clearly 1, 2 and 3 with the fourth a NEGATIVE sign
!!!!!!!!!!!!!
Are they? Their order is a bit strange if so.

On the other hand, take the - to be a 1, and the other symbol to be a 4
with a bit missing,

This is how right-pondians write the numeral "1". They also cross their
"7"s. ;-)
Click to expand...
Sometimes cross a 7 if the need arises, but it's not so common in the uk
as it is on 'the continent'.

We may have signed up to some of the eu insanity, but we are far from
hearts and minds for the revised 1000 year reich / european federal
superstate / new world order :-(...

Regards,

Chris
 
On Sat, 14 Nov 2009 08:07:37 +1100, "Phil Allison" <phil_a@tpg.com.au>
wrote:

"Shaun"

I looked up inrush current for transformers and I stand corrected, it's
maximum will occur at the voltage zero crossing point. I thought it was
the same as an L R circuit in which case if switch closes as the peak of
the ac waveform it causes the maximum transient.

A bit off topic....
Click to expand...
At first thought, it seems counter-intuitive that zero-crossing is
the worst case for inrush current, so I used LTSPICEIV to simulate the
situation. As usual Phil is correct! here's the .asc file for the
simulation, note that you must set the inductor current to zero for
the initial condition.

Version 4
SHEET 1 880 680
WIRE 192 80 48 80
WIRE 336 80 272 80
WIRE 48 112 48 80
WIRE 336 144 336 80
WIRE 48 224 48 192
WIRE 336 224 48 224
WIRE 48 256 48 224
FLAG 48 256 0
SYMBOL voltage 48 96 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value SINE(0 160 60 0 0 0 10)
SYMBOL res 320 128 R0
SYMATTR InstName R1
SYMATTR Value 5
SYMBOL ind 176 96 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 5 56 VBottom 0
SYMATTR InstName L1
SYMATTR Value 1
TEXT 80 272 Left 0 !.tran 0 0.2 0.00001 0.00001
TEXT 88 304 Left 0 !.IC i(L1)=0

In the sim above, is a 1H inductor in series with 5 ohms, with
110vac (160v peak) applied. The voltage is set to start at zero
crossing.
Afterward, set the phase of the voltage to 90degrees, and you'll see
that the current is less. In the above sim, the AC current has +/- 400
mA peaks (800mA p-p) when you start at sinewave of 90 degrees.
Starting at sinewave zero degrees, the current STARTS at 0.0 mA,then
goes to about +800mA, then gradually loses the DC component.
When the AC supply is switched off, you also get interesting
results! When switched off at zero-crossing, there is still
considerable DC current flowing in the inductor. It will cause a lot
of trouble if not taken into account. When switched off at the +/-
peak of the sine wave, the inductor current will be zero. In other
words, inductive loads are happier being switched at the +/- peaks,
which is not what you might expect, if you are used to capacitive
input power supplies.

** Now you owe me a big apology.


BTW: Phil you are very RUDE!!


** Drop dead you tedious wanker.


..... Phil
Click to expand...
Phil has pretty good advice, but he sure gets irritated if you
don't know what you're doing. You'll get absolutely nowhere biting him
back, unless you can decently support what seems to be your mistake.
There's a lot to learn from his "critiques", but some of the back &
forth rants are pretty silly. It's always fun to watch a "Phil"
thread!

Paul G.
 
Paul G. wrote:
On Sat, 14 Nov 2009 08:07:37 +1100, "Phil Allison" <phil_a@tpg.com.au
wrote:


"Shaun"

I looked up inrush current for transformers and I stand corrected, it's
maximum will occur at the voltage zero crossing point. I thought it was
the same as an L R circuit in which case if switch closes as the peak of
the ac waveform it causes the maximum transient.

A bit off topic....
At first thought, it seems counter-intuitive that zero-crossing is
the worst case for inrush current,
Click to expand...
To make it more intuitive, consider that starting at 0 crossing
provides more time charging the inductance, so higher I.

Ed

so I used LTSPICEIV to simulate the
situation. As usual Phil is correct! here's the .asc file for the
simulation, note that you must set the inductor current to zero for
the initial condition.
Click to expand...
 
"Paul G."
"Phil Allison"
"Shaun"

I looked up inrush current for transformers and I stand corrected, it's
maximum will occur at the voltage zero crossing point. I thought it was
the same as an L R circuit in which case if switch closes as the peak of
the ac waveform it causes the maximum transient.

A bit off topic....
At first thought, it seems counter-intuitive that zero-crossing is
the worst case for inrush current, so I used LTSPICEIV to simulate the
situation. As usual Phil is correct! here's the .asc file for the
simulation, note that you must set the inductor current to zero for
the initial condition.

( snip listing)

In the sim above, is a 1H inductor in series with 5 ohms, with
110vac (160v peak) applied. The voltage is set to start at zero
crossing.
Click to expand...
** Your simulation is of an inductor - and NOT a AC supply transformer
primary as the question requires.

The differences are many and great and the switch on transient behaviour
very different - mostly because a transformer's laminated iron core will
saturate hard when a frequency just a little lower than it is designed for
is applied.

I doubt that LTSPICE IV can even do such a simulation.

Its why I said to TRY it !!


Phil has pretty good advice, but he sure gets irritated if you
don't know what you're doing. You'll get absolutely nowhere biting him
back, unless you can decently support what seems to be your mistake.
Click to expand...
** Yep - there is nowhere to stat demolishing a fallacy if no sensible case
is posted that supports it.

Posting inane drivel like " .think about it " or " I am surprised you don't
know this " is just pouring fuel on the fire.



...... Phil
 
"ehsjr"
To make it more intuitive, consider that starting at 0 crossing
provides more time charging the inductance, so higher I.
Click to expand...
** But we are discussing the behaviour of a AC supply TRANSFORMER - where
core saturation IS the cause of inrush current surges.

The simplest way to think about it is to first note that the core of nearly
any AC supply tranny operates on the edge of saturation ALL THE TIME when
mains power is applied.

( Proof of this is that if one raises the applied voltage by about 20% or
lowers the AC frequency by the same - the magnetising current drawn by the
tranny will dramatically increase. )

The note that switching the supply on at a zero crossing means the *average
value* of the wave will not become zero until a whole cycle has passed -
while switching on at a peak means only half a cycle need pass for the same
result.

The second case produces a very much smaller inrush surge as a result.

Interestingly, if the AC voltage applied to a supply tranny is half or less
its rated operating voltage - inrush current surges barely exist.


...... Phil
 
On Sun, 15 Nov 2009 11:31:08 -0600, John Fields
<jfields@austininstruments.com> wrote:

I developed this subcircuit when modeling some aircraft lamp
drivers....

****
** AIRCRAFT LAMP SUBCIRCUIT
*VO=NOMINAL OPERATING VOLTAGE
*IO=NOMINAL STEADY STATE OPERATING CURRENT
*RCOLD=FILAMEMT RESISTANCE MEASURED AT ROOM TEMP (300K)
*TAU=CURRENT TIME CONSTANT AFTER A 0 (zero) TO VO STEP IS APPLIED
..SUBCKT LAMP 1 2 PARAMS: VO=28 IO=25m RCOLD=112 TAU=22m TAMB=300
H1 6 0 VML 1
RH1 6 0 1
GP 0 4 VALUE={V(6)*V(1,2)}
*V(4,0) = FILAMENT TEMPERATURE IN KELVINS
RT 4 5 {300*(VO-IO*RCOLD)/(IO*IO*VO*RCOLD)}
CT 4 5 {TAU*IO*IO*VO*RCOLD/(300*(VO-IO*RCOLD))}
VAMB 5 0 {TAMB}
El 7 0 1 2 300
R1 7 0 1
E2 8 0 VALUE={V(4)*RCOLD}
R2 8 0 1
E3 10 0 7 9 10MEG
R3 10 0 1
E4 9 0 VALUE={V(8)*V(10)}
R4 9 0 1
GR 1 3 10 2 1
VML 3 2 0
..ENDS LAMP
****

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

If you wanted a President with balls why didn't you elect Hillary?
 
"Fred Abse" <excretatauris@invalid.invalid> wrote in message
news:pan.2009.11.15.12.22.20.462046@invalid.invalid...
On Sun, 15 Nov 2009 02:29:30 -0800, Bob E. wrote:

My experience is that there are true RMS clamp meters that measure
current
via max/peak method and newer meters that use the in-rush method (ie,
Fluke 330 series).

Accurate measurement of in-rush current has alway been possible since the
advent of true RMS meters with Max feature. Fluke is now touting the
triggered 100mS inrush measurement feature as the new "must-have" thing.

How much more useful than a good true RMS clamp meter with max/hold is a
triggered 100mS meter? For measurement of synchronous motor currents
(with
and without adjustable speed drives (ASDs)), is a trigger or a fast
measurement really necessary? Helpful? A waste?

What do you think?

Read Fluke application note 1629920 and work it out.

Could you provide a link to that document, because I can't find it.
Click to expand...

Shaun
 
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