Fuses in place of motor "heaters"? (induction motor protecti

[DoN. Nichols]

On 2014-01-26, bud-- <null@void.com> wrote:

On 1/25/2014 7:10 AM, Mike Marlow wrote:
DaveC wrote:
Looking to provide switching for 1-phase, 220 AC, 1/2 hp motor that
doesn't include use of a contactor. I appreciate the need for precise
current limit (LRA) that a branch breaker can't provide.

[ ... ]

Would 2 precisely-matched (ie, to the 1/4 amp), slow-blow HRC fuses be
sufficient to protect this motor?

To the 1/4 A out of what rating? 1/4 A out of a 1/4 A fuse is
a pretty big error. 1/4 A out of a 50 A fuse is a lot less.

In other words, what kind of percentage? And the curves for
fuses don't say *when* it will blow, they simply say that it must
tolerate full load amps for N hours, and for each increment above that,
they have to blow within a certain time. They can be quicker, but not
slower.

How are you going to find fuses that precisely matched? You
can't really *know* that they are that precisely matched until you have
tested them -- by which time they are now blown, and thus useless,
except perhaps as a poor insulator.

May or may not, depending on the fuse characteristics. The fuse has to
be slow-blow enough to not open when the motor starts (starting current
is about 6x running current). But it has to open within the i-squared-t
rating of the motor (as in Jim's post).

The "overloads" in motor starters are matched to motor starting. And the
settings in are much finer steps (or are continuous) compared to fuses.

Many 1/2HP motors have internal overload protection ("thermally protected").

Some of those are thermal fuses (cooked off by the heat in the
windings) buried in the windings. When that goes, you can't access it
to replace it -- except by re-winding the motor. They don't re-set on
their own.

Enjoy,
DoN.

--
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[Phil Allison]

"bud--"

Phil Allison wrote:
"bud--"

May or may not, depending on the fuse characteristics. The fuse has to
be
slow-blow enough to not open when the motor starts (starting current is
about 6x running current). But it has to open within the i-squared-t
rating of the motor (as in Jim's post).

** Think you will have poor luck with a HRC fuse taking 6 time rated
every
time the motor starts or stalls and not nuisance blowing.

Fuses are not usually used for motor overload protection in the US. There
aren't enough fuse ratings to match to the motor running current except
for relatively small motors.


A "motor start" circuit breaker is what is normally used.

Slow, thermal characteristic at up to 6 times and then a very fast
magnetic
action at about 10 times.


Time delay breakers can be up to 175% of the motor running current in the
US.

** Blah, blah, blah...

They often are used for short circuit protection of a motor circuit, but
not for overload protection.

** Horse manure !!!!!!!!!!

Overload protection is EXACTLY what circuit breakers are there for.

You cab size them to protect a stalled or overloaded motor or just the
supply cables.



..... Phil

 

[bud--]

On 1/26/2014 11:00 PM, Phil Allison wrote:

"bud--"
Phil Allison wrote:
"bud--"

May or may not, depending on the fuse characteristics. The fuse has to
be
slow-blow enough to not open when the motor starts (starting current is
about 6x running current). But it has to open within the i-squared-t
rating of the motor (as in Jim's post).

** Think you will have poor luck with a HRC fuse taking 6 time rated
every
time the motor starts or stalls and not nuisance blowing.

Fuses are not usually used for motor overload protection in the US. There
aren't enough fuse ratings to match to the motor running current except
for relatively small motors.


A "motor start" circuit breaker is what is normally used.

Slow, thermal characteristic at up to 6 times and then a very fast
magnetic
action at about 10 times.


Time delay breakers can be up to 175% of the motor running current in the
US.

** Blah, blah, blah...

They often are used for short circuit protection of a motor circuit, but
not for overload protection.

** Horse manure !!!!!!!!!!

Overload protection is EXACTLY what circuit breakers are there for.

You cab size them to protect a stalled or overloaded motor or just the
supply cables.

The step between circuit breaker ratings is far too large to provide
overload protection for motors. What I described is exactly what is in
the US NEC and what practice is in the US.

Must be another alwayswrong sock puppet.

 

[Phil Allison]

"boob = bullshit artist "

Phil Allison wrote:



A "motor start" circuit breaker is what is normally used.

Slow, thermal characteristic at up to 6 times and then a very fast
magnetic action at about 10 times.


Time delay breakers can be up to 175% of the motor running current in
the
US.

** Blah, blah, blah...

They often are used for short circuit protection of a motor circuit, but
not for overload protection.

** Horse manure !!!!!!!!!!

Overload protection is EXACTLY what circuit breakers are there for.

You cab size them to protect a stalled or overloaded motor or just the
supply cables.


The step between circuit breaker ratings is far too large to provide
overload protection for motors.

** FFS - asshole try LEARNING TO READ

Thermal breakers come in any almost size you like and you fit them between
the AC outlet and the load.

Thermal/ magnetic breakers are not simply for "short circuit protection".

They provide cable overload ( overtemp) protection.

Fucking moron.


.... Phil

 

[bud--]

On 1/27/2014 4:58 PM, Phil Allison wrote:

"boob = bullshit artist"

Phil Allison wrote:



A "motor start" circuit breaker is what is normally used.

Slow, thermal characteristic at up to 6 times and then a very fast
magnetic action at about 10 times.


Time delay breakers can be up to 175% of the motor running current in
the
US.

** Blah, blah, blah...

They often are used for short circuit protection of a motor circuit, but
not for overload protection.

** Horse manure !!!!!!!!!!

Overload protection is EXACTLY what circuit breakers are there for.

You cab size them to protect a stalled or overloaded motor or just the
supply cables.


The step between circuit breaker ratings is far too large to provide
overload protection for motors.

** FFS - asshole try LEARNING TO READ

Perhaps you could read. US NEC sizes breakers up to 175% of motor run
current. Wire is 115% of motor run current.

Thermal breakers come in any almost size you like and you fit them between
the AC outlet and the load.

What breaker would you use for overload protection for a motor with a
run current of 16.3A. Breaker must be UL listed, able to withstand motor
starting currents, and suitable for use as motor protection.

Thermal/ magnetic breakers are not simply for "short circuit protection".

They provide cable overload ( overtemp) protection.

Not in the US NEC. And not the practice in the US.

Fucking moron.

You have such compelling arguments.

 

[Phil Allison]

"boob = bullshit artist"

They often are used for short circuit protection of a motor circuit,
but
not for overload protection.

** Horse manure !!!!!!!!!!

Overload protection is EXACTLY what circuit breakers are there for.

You cab size them to protect a stalled or overloaded motor or just the
supply cables.


The step between circuit breaker ratings is far too large to provide
overload protection for motors.

** FFS - asshole try LEARNING TO READ

Thermal breakers come in any almost size you like and you fit them
between
the AC outlet and the load.

Thermal/ magnetic breakers are not simply for "short circuit protection".

They provide cable overload ( overtemp) protection.

Not in the US NEC. And not the practice in the US.

** You are one stupid, lying ass.

WTF do you think AC supply circuit breakers are fucking for?
--------------------------------------------------------------------

You have such compelling arguments.

** While you have posted NONE at ALL !!!!!!!!

Fuck off - you crazy fucking nut case.



..... Phil

 

[bud--]

On 1/28/2014 5:41 PM, Phil Allison wrote:

"boob = bullshit artist"

They often are used for short circuit protection of a motor circuit,
but
not for overload protection.

** Horse manure !!!!!!!!!!

Overload protection is EXACTLY what circuit breakers are there for.

You cab size them to protect a stalled or overloaded motor or just the
supply cables.


The step between circuit breaker ratings is far too large to provide
overload protection for motors.

** FFS - asshole try LEARNING TO READ

Thermal breakers come in any almost size you like and you fit them
between
the AC outlet and the load.

Thermal/ magnetic breakers are not simply for "short circuit protection".
They provide cable overload ( overtemp) protection.

Not in the US NEC. And not the practice in the US.

** You are one stupid, lying ass.

More of the famous Allison logic.

WTF do you think AC supply circuit breakers are fucking for?

You forgot to to answer the question. Maybe because you deleted it.
"What [AC supply circuit] breaker would you use for overload protection
for a motor with a run current of 16.3A. Breaker must be UL listed, able
to withstand motor starting currents, and suitable for use as motor
protection."

That should be a trivial you.

You have such compelling arguments.


** While you have posted NONE at ALL !!!!!!!!

Only if you can't read !!!!!!!!

Fuck off - you crazy fucking nut case.

Does you mommy approve of your language?

 

[gregz]

Fred Abse <excretatauris@invalid.invalid> wrote:

On Sun, 26 Jan 2014 08:13:56 -0500, Jim Wilkins wrote:

"DoN. Nichols" <BPdnicholsBP@d-and-d.com> wrote in message
news:slrnle97cu.5kc.BPdnicholsBP@Katana.d-and-d.com...
On 2014-01-25, Jim Wilkins <muratlanne@gmail.com> wrote:

Why do you need two fuses for a single-phase motor?

In the UK, you don't, because 240 VAC comes with one side grounded.
However, in the USA, 240 VAC is normally supplied with a grounded center
tap, so if you have only one fuse -- or have two but only one blows, you
still have 120 VAC live in the motor's housing, and
potentially available for contact and personal zapping.


I assumed it was wired with a 20A double-pole breaker at the panel
protecting from shorts and a smaller fuse sized (how?) to blow before the
motor burned out.


Panel breakers are there to protect the upstream wiring from excessive
load current, not to protect the load.

Matching the I-squared-t of a breaker, or fuse, to startup and running
conditions of a motor is not trivial. Motors are subject to starting
inrush currents sometimes tens of times the rated full-load current. Be
guided by the data published by reputable manufacturers. There's plenty of
it.

My ac compressor unit says, use 20 amp breaker. The wiring said nothing.

Greg

 

[Michael A. Terrell]

bud-- wrote:

Must be another alwayswrong sock puppet.

No, this is a different character. A psychotic Aussie.

 

[bud--]

On 1/29/2014 11:23 PM, gregz wrote:

Fred Abse <excretatauris@invalid.invalid> wrote:
On Sun, 26 Jan 2014 08:13:56 -0500, Jim Wilkins wrote:

"DoN. Nichols" <BPdnicholsBP@d-and-d.com> wrote in message
news:slrnle97cu.5kc.BPdnicholsBP@Katana.d-and-d.com...
On 2014-01-25, Jim Wilkins <muratlanne@gmail.com> wrote:

Why do you need two fuses for a single-phase motor?

In the UK, you don't, because 240 VAC comes with one side grounded.
However, in the USA, 240 VAC is normally supplied with a grounded center
tap, so if you have only one fuse -- or have two but only one blows, you
still have 120 VAC live in the motor's housing, and
potentially available for contact and personal zapping.


I assumed it was wired with a 20A double-pole breaker at the panel
protecting from shorts and a smaller fuse sized (how?) to blow before the
motor burned out.


Panel breakers are there to protect the upstream wiring from excessive
load current, not to protect the load.

Matching the I-squared-t of a breaker, or fuse, to startup and running
conditions of a motor is not trivial. Motors are subject to starting
inrush currents sometimes tens of times the rated full-load current. Be
guided by the data published by reputable manufacturers. There's plenty of
it.


My ac compressor unit says, use 20 amp breaker. The wiring said nothing.

The manufacturer tells you what size breaker will withstand the starting
current and provide protection from manor failures.

Overload protection is very likely a thermal trip on the compressor.
Small fans are "impedance" protected.

 

[josephkk]

On Wed, 29 Jan 2014 14:28:16 -0600, bud-- <null@void.com> wrote:

On 1/28/2014 5:41 PM, Phil Allison wrote:
"boob = bullshit artist"

They often are used for short circuit protection of a motor circuit,
but
not for overload protection.

** Horse manure !!!!!!!!!!

Overload protection is EXACTLY what circuit breakers are there for.

You cab size them to protect a stalled or overloaded motor or just the
supply cables.


The step between circuit breaker ratings is far too large to provide
overload protection for motors.

** FFS - asshole try LEARNING TO READ

Thermal breakers come in any almost size you like and you fit them
between
the AC outlet and the load.

Thermal/ magnetic breakers are not simply for "short circuit protection".
They provide cable overload ( overtemp) protection.

Not in the US NEC. And not the practice in the US.

** You are one stupid, lying ass.

More of the famous Allison logic.


WTF do you think AC supply circuit breakers are fucking for?

You forgot to to answer the question. Maybe because you deleted it.
"What [AC supply circuit] breaker would you use for overload protection
for a motor with a run current of 16.3A. Breaker must be UL listed, able
to withstand motor starting currents, and suitable for use as motor
protection."

That should be a trivial you.


You have such compelling arguments.


** While you have posted NONE at ALL !!!!!!!!

Only if you can't read !!!!!!!!


Fuck off - you crazy fucking nut case.

Does you mommy approve of your language?

For real horror to think he eats with that mouth.

?-)