Unwinding of power extension cords

[Bob]

Firstly, apologies for the electrical question in an electronic group.

I always thought the reason for having to unwind extension cords was to
prevent creating an inductive loop (?) and/or increasing the resistance of
the wire.

Lately though I have read at least a few times that leaving them coiled up
more simply just doesn’t allow the “heat to escape”.

So is the situation A, B, or A->B?

I guess the practical difference is that B implies that a coil is fine, as
long as it’s a somewhat loose coil. So what’s real here?

 

[Phil Allison]

Bob wrote:

------------

Firstly, apologies for the electrical question in an electronic group.

** We all use electricity and have ot know about it.

I always thought the reason for having to unwind extension cords was to
prevent creating an inductive loop (?) and/or increasing the resistance of
the wire.

** LOL - that is nonsense.

AC power cords have the Active an Neutral conductors twisted around each other, minimising any included loop area. Inductance at 50Hz is completely swamped by copper resistance.

Lately though I have read at least a few times that leaving them coiled up
more simply just doesn’t allow the “heat to escape”.

** Correct, at rated load the plastic insulation will melt an ruin the cord..

Even running cords under thick carpet or bundled with others is a bad idea.

People's homes have burnt down because of it.


.... Phil

 

[Xeno]

On 16/11/19 2:35 pm, Bob wrote:

Firstly, apologies for the electrical question in an electronic group.

I always thought the reason for having to unwind extension cords was to
prevent creating an inductive loop (?) and/or increasing the resistance of
the wire.

Lately though I have read at least a few times that leaving them coiled up
more simply just doesn’t allow the “heat to escape”.

So is the situation A, B, or A->B?

I guess the practical difference is that B implies that a coil is fine, as
long as it’s a somewhat loose coil. So what’s real here?

Both!

If they are close coiled, yes, heat cannot escape. If they are close
coiled, more heat is generated. A double whammy.

--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

 

[Phil Allison]

Xeno wrote:

-=-----------

Bob wrote:
Firstly, apologies for the electrical question in an electronic group.

I always thought the reason for having to unwind extension cords was to
prevent creating an inductive loop (?) and/or increasing the resistance of
the wire.

Lately though I have read at least a few times that leaving them coiled up
more simply just doesn’t allow the “heat to escape”.

So is the situation A, B, or A->B?

I guess the practical difference is that B implies that a coil is fine, as
long as it’s a somewhat loose coil. So what’s real here?

Both!

If they are close coiled, yes, heat cannot escape. If they are close
coiled, more heat is generated. A double whammy.

** More accurately, when coiled cooling by air convection is inhibited.

When layered as well, the surface area exposed for cooling is much smaller.

The heat in Watts follows the "I squared R" rule - so as the cable rises to a higher temp than otherwise the R value rises too so the is more heat for the same load.

R increase = 1 + temp rise / 245 in degrees C



..... Phil

 

[Xeno]

On 17/11/19 8:26 am, Phil Allison wrote:

Xeno wrote:

-=-----------
Bob wrote:
Firstly, apologies for the electrical question in an electronic group.

I always thought the reason for having to unwind extension cords was to
prevent creating an inductive loop (?) and/or increasing the resistance of
the wire.

Lately though I have read at least a few times that leaving them coiled up
more simply just doesn’t allow the “heat to escape”.

So is the situation A, B, or A->B?

I guess the practical difference is that B implies that a coil is fine, as
long as it’s a somewhat loose coil. So what’s real here?

Both!

If they are close coiled, yes, heat cannot escape. If they are close
coiled, more heat is generated. A double whammy.


** More accurately, when coiled cooling by air convection is inhibited.

When layered as well, the surface area exposed for cooling is much smaller.

The heat in Watts follows the "I squared R" rule - so as the cable rises to a higher temp than otherwise the R value rises too so the is more heat for the same load.

R increase = 1 + temp rise / 245 in degrees C



..... Phil

I was thinking more in terms of induction heating in a coil with AC
currents. It isn't just the inability to cool the coil.

--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

 

[Rheilly Phoull]

On 17/11/2019 3:53 pm, Xeno wrote:

On 17/11/19 8:26 am, Phil Allison wrote:
Xeno wrote:

-=-----------
Bob wrote:
Firstly, apologies for the electrical question in an electronic group.

I always thought the reason for having to unwind extension cords was to
prevent creating an inductive loop (?) and/or increasing the
resistance of
the wire.

Lately though I have read at least a few times that leaving them
coiled up
more simply just doesn’t allow the “heat to escape”.

So is the situation A, B, or A->B?

I guess the practical difference is that B implies that a coil is
fine, as
long as it’s a somewhat loose coil. So what’s real here?

Both!

If they are close coiled, yes, heat cannot escape. If they are close
coiled, more heat is generated. A double whammy.


** More accurately, when coiled cooling by air convection is inhibited.

When layered as well, the surface area exposed for cooling is much
smaller.

The heat in Watts follows the "I squared R" rule - so as the cable
rises to a higher temp than otherwise the R value rises too so the is
more heat for the same load.

  R increase  = 1 + temp rise / 245   in degrees C



.....   Phil

I was thinking more in terms of induction heating in a coil with AC
currents. It isn't just the inability to cool the coil.

The cores being twisted alleviate that.

 

[Phil Allison]

Xeno wrote:

-----------

** More accurately, when coiled cooling by air convection is inhibited.

When layered as well, the surface area exposed for cooling is much smaller.

The heat in Watts follows the "I squared R" rule - so as the cable rises
to a higher temp than otherwise the R value rises too so the is more
heat for the same load.

R increase = 1 + temp rise / 245 in degrees C


I was thinking more in terms of induction heating in a coil with AC
currents.

** There is no coil in this situation.

Induction heating uses Magnetism & Eddy Currents, also absent here.

Winding a twisted pair cable on a drum adds no inductance.


...... Phil

 

[amdx]

On 11/17/2019 4:49 AM, Phil Allison wrote:

Xeno wrote:

-----------

** More accurately, when coiled cooling by air convection is inhibited.

When layered as well, the surface area exposed for cooling is much smaller.

The heat in Watts follows the "I squared R" rule - so as the cable rises
to a higher temp than otherwise the R value rises too so the is more
heat for the same load.

R increase = 1 + temp rise / 245 in degrees C


I was thinking more in terms of induction heating in a coil with AC
currents.



** There is no coil in this situation.

Induction heating uses Magnetism & Eddy Currents, also absent here.

Winding a twisted pair cable on a drum adds no inductance.


..... Phil

Just for fun, I once saw a welder attempting to do some (Mig?) welding
from his trailer mounted welder. (he was welding aluminum) The welder
had an internal spark gap to generate High frequency to start the arc.
He was having a hard time getting his welder to arc properly until he
uncoiled the welding cable off the trailer. Once he did that it work great.

Three weeks ago you posted a puzzle over on SED, and then died, or
that's what all your pals thought!
Are you going to finish the thread?

 

[boB]

On Sun, 22 Dec 2019 15:17:17 -0600, amdx <nojunk@knology.net> wrote:

On 11/17/2019 4:49 AM, Phil Allison wrote:
Xeno wrote:

-----------

** More accurately, when coiled cooling by air convection is inhibited.

When layered as well, the surface area exposed for cooling is much smaller.

The heat in Watts follows the "I squared R" rule - so as the cable rises
to a higher temp than otherwise the R value rises too so the is more
heat for the same load.

R increase = 1 + temp rise / 245 in degrees C


I was thinking more in terms of induction heating in a coil with AC
currents.



** There is no coil in this situation.

Induction heating uses Magnetism & Eddy Currents, also absent here.

Winding a twisted pair cable on a drum adds no inductance.


..... Phil


Just for fun, I once saw a welder attempting to do some (Mig?) welding
from his trailer mounted welder. (he was welding aluminum) The welder
had an internal spark gap to generate High frequency to start the arc.
He was having a hard time getting his welder to arc properly until he
uncoiled the welding cable off the trailer. Once he did that it work great.

Three weeks ago you posted a puzzle over on SED, and then died, or
that's what all your pals thought!
Are you going to finish the thread?

Yes. We are waiting for you, Phil.

I am guessing that you have gone away because one of us got it
right... but you have so much vial hatred for everybody so that you
cannot admit that. Being that way can not be good for ones' health.

 

[Bob]

boB <boB@K7IQ.com> wrote:

Yes. We are waiting for you, Phil.

I am guessing that you have gone away because one of us got it
right... but you have so much vial hatred for everybody so that you
cannot admit that. Being that way can not be good for ones' health.

Do I need to change my name?

 

[news18]

On Tue, 24 Dec 2019 12:34:15 +0000, Bob wrote:

boB <boB@K7IQ.com> wrote:


Yes. We are waiting for you, Phil.

I am guessing that you have gone away because one of us got it right...
but you have so much vial hatred for everybody so that you cannot
admit that. Being that way can not be good for ones' health.

Do I need to change my name?

Surely no to Bruce!