Unwinding of power extension cords

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?

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

f
** LOL - that is nonsense.

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

p

?.

** 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

Reply to
Phil Allison

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. 
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Reply to
Xeno

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** 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

Reply to
Phil Allison

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. 
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Reply to
Xeno

The cores being twisted alleviate that.

Reply to
Rheilly Phoull

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** 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

Reply to
Phil Allison

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?

Reply to
amdx

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.

Reply to
boB

Do I need to change my name?

Reply to
Bob

Surely no to Bruce!

Reply to
news18

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