J. Clarke wrote:
WillR wrote:
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=20
Roy Smith wrote:
Leon wrote:
If anything a lower rated circuit breaker is going to make the motor
heat up more when under a strain because it is not getting enough
power.
Enough current???? Have actually seen this -- in a failure mode of a
breaker - ALTAIALFA (a long time ago in a land far away) But it was a
handful of failures in thousands of machines. Highly unlikely -- but
maybe not impossible. I will leave it to the EE's in the group who migh=
t
want to debate this. I am sure that someone here can do some
calculations and dig up some data to prove something. I certainly
can't/won't these days.
Ugh. Where do people get this stuff from? A breaker either stays
closed or it opens. If it's closed, the circuit will deliver as much
power as the load can draw (minus resistive losses in the wiring
itself). If it opens, there's no power delivered. There is no middle=
ground where the breaker is not delivering "enough power".
And if the breaker fails by developing a higher resistance?
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=20
Then how does it make any difference if the breaker is rated for 1 amp =
or a
billion? If the failure is corrosion of the contacts or something else=
that causes increased resistance in the contacts it's going to occur on=
a
breaker of any capacity.
=20
Sounds reasonable.
The contacts are simply metal touching metal. They may be exactly the =
same
size in breakers with a very wide range of current capacities. What ma=
kes
the breaker "break" is a mechanism that opens those contacts, not anyth=
ing
having to do with their innate properties.
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Have to agree with that assessment.
=20
Actually=20
seen this in a handful of failures out of many thousands of
motor/breaker circuits in a manufacturing situation. I was just glad I
could pass the analysis to someone competent. Again ALTAIALFA -- QA is
probably a lot better and techniques have changed -- so it probably
doesn't happen any more...
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=20
So? Having a larger breaker would have made no difference.
=20
And probably not even a smaller one. Don't know any more -- any more.
As soon as I could I stick to pure logic, and ittsy bittsy things that=20
couldn't pull my fingers off I was happier the motors were happier -- it =
was a win-win.
Packets, bits, bytes, words, core memories, adders -- they were all so=20
much simpler -- and if you hit them with a hammer they did not rotate=20
back at you and eat your finger -- or eat their breakers if you shorted=20
their contacts.
Motors -- especially ones with breakers and servos were (to me)=20
inherently untrustworthy...
Hope that explains my position.
=20
I am beginning to wish that we had the Chemists equivalent of STP
(Standard Temperature and Pressure)
Then we could all say that when we mean when we say "normally" -- which=
isn't used often enough...
Then we wouldn't debate this stuff unless it was egregious enuff to
really rile us up. I am so MAD!!! Cause I saw some of these failures 30=
years ago and -- IT CAN HAPPEN! I SWEAR! TO DENY IT IS WRONG!!!!
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=20
There is no question that breakers can fail in various ways. The quest=
ion
is whether using a larger one would eliminate the kind of malfunction t=
hat
you observed, and there is no reason to believe that it would.
=20
Don't think I was arguing that -- for or against. Just pointing out how=20
grateful I was that somebody competent that worked with me could help.
Just just plaintively whining that I wish we had standards like STP so=20
we could discuss things easier -- beyond that...
=20
And I swore I would never post on one of these threads. But if a cool
head like Robatoy can give at least one shot I will allow myself _once_=
=2E
Did I mention I HATE COMPOUND MITER DESIGNS?
I swear by the Red Green payer that I will do this no more. I swear...
OKOK AMT. Breathe deep.
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=20
This was twice -- shudder!!! Hopefully I have displayed complete=20
incompetence and If I ever post in an electrical thread again will be=20
turfed as quickly as possible.
Unless, of course, you want all the calculations done in Mod 11 or Mod=20
13 -- I can do that. Ohms law and Helmholtz equations - calculated in=20
Mod 13 -- now there's a thought... Insane -- yes but still a thought.
In a matrix - LU factorization would make it easy --- yes it could work.
:-)
--=20
Will R.
Jewel Boxes and Wood Art
http://woodwork.pmccl.com
The power of accurate observation is commonly called cynicism by those=20
who have not got it.=94 George Bernard Shaw