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Cable Copper Thickness

06/12/2010 7:54 AM

I want to know how the thickness of a 60 HP slip ring induction motor cabling for overhead crane from 1.5MVA transformer is done. What are the parameter to be considered, i have a slight idea that we should consider short circuit current. Please explain with formulae.

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Anonymous Poster
#1

Re: Cable Copper thickness

06/12/2010 9:36 AM

is this motor directly connected to Transformer?...The main parameters to be considered is the thickness of overhead crane, height of the crane should be less than the height of transformer. Short circuit current means the current in the short length of the circuit. Measure the length of the circuit and consider it.

Formulae:- Sc= L x I/ZxY.

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Guru

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#2

Re: Cable Copper thickness

06/12/2010 10:19 AM

Hire a competent electrician. Having a slight idea about 45 Kw will get someone killed. And, unfortunately, it might be someone other than just you.

This is not a DIY project.

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#3
In reply to #2

Re: Cable Copper thickness

06/12/2010 10:48 AM

I want to learn its just a study.I am asking your help to learn nobody authorise me to do it. I didnt hide my identity.I am facing a lot of problems just because i am straight forward?

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Guru

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#4
In reply to #3

Re: Cable Copper thickness

06/12/2010 11:08 AM

I quote from one of your earlier characteristically elementary questions,

"How does a tester work? I have done checking phase and myself as ground but Ii never understand why I'm not getting shocked.The circuit is closed now, is it the resistance in series or vacuum in bulb or a positive charge is developed from ground? Please help I'm a graduate EE."

What did you learn in school?

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#5
In reply to #4

Re: Cable Copper thickness

06/12/2010 11:18 AM

We didnt learn about a tester we have to understand it from what ever higher circuit numericals we do.I was deliberatly in need of answer and i want to bring the situation going on here to the public.I know you people mean the very designation as Engineer now please forgive me and be kind to help me sir.

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Guru
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#6

Re: Cable Copper Thickness

06/12/2010 11:24 AM

They extrude single strands of copper size depending on how much flexibility the final cable needs to have. Then the twist them together into a stranded wire to handle amperage in excess of the load of the motor at the working voltage. They then cover the strands with insulation which would have the flexibility needed and the insulating properties to the working voltage. Parameter are amperage, voltage and flexibility. Short circuit current is what breakers are for in distribution panels to protect the wires. Motors are protected with fuses or thermal overloads. There is not just one formula for all you wish to know. Each manufacture of cable has his own. They maybe similar but there may be some differences. Could just be twists per foot.

Not quite the answer you expected?

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#7
In reply to #6

Re: Cable Copper Thickness

06/12/2010 11:49 AM

Thank you Mr. Ozzb i was expecting a general formula.whatever you said is what happens in a manufacturing unit right. So what you mean the twisted cable can withstand short circuit current even though we wired it for specific current only.In fault conditions the breakers (MCBs) takes some time know and i wonder how the wire could withstand it ? We use HRC fuses here i hope that is for cable protection and its rated capacity is high.

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Anonymous Poster
#8
In reply to #7

Re: Cable Copper Thickness

06/12/2010 11:52 AM

Dont question us. Just beleive what we americans say.

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#9
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Re: Cable Copper Thickness

06/12/2010 12:06 PM

I believe mathematics. Who said "what is most important is not to stop asking" ? I Believe Americans are good people, they feel happy to share knowledge.

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#18
In reply to #8

Re: Cable Copper Thickness

09/12/2010 8:58 AM

Hmmmmmmmmmmmmm

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#10
In reply to #6

Re: Cable Copper Thickness

06/12/2010 3:15 PM

GA ozzb.

The thing is that many of the things that has to be considered in an appropriate choice of any cable are critical parameters that cannot quantified. (i.e. flexibility, insulation durability to abrasion, ultra-violet radiation, chemical exposure, temperature extremes, icing) This is why a continuous function equation, linear or non-linear, cannot be made. So regional code standards have been made that have look up tables that must be translated by a knowledgeable person.

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#11
In reply to #10

Re: Cable Copper Thickness

06/13/2010 8:18 PM

But atleast for understanding the Amp. rating there will be a calculation?

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Guru
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#12
In reply to #11

Re: Cable Copper Thickness

06/13/2010 10:37 PM

No, not even the amperage rating of a certain conducting area of copper can be calculated. Given a copper wire sheathed in teflon with a cross sectional area of "x" that is able to safely and continuously dissipate the power created by amperage "J" will only require a smaller fraction of the same cross sectional area "x/y" copper wire if the insulation of the same thickness is Kapton reinforced by fiberglass. For the Kapton and fiberglass insulation will not deform and short out the wiring at the same temperature. If one were to immerse the cable in an insulating and also heat removing oil bath then even less wire thickness is required for safe continuous duty. Also the duty cycle of the current can play greatly into this problem. I have a device that regularly delivers hundreds of amperes of current through wire no greater than one millimeter square in cross sectional area suspended in a vacuum chamber with absolutely no additional cooling provided. It's done for only 20 micro seconds and no more often than four times an hour but it is regularly done without failure.

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#14
In reply to #12

Re: Cable Copper Thickness

06/14/2010 3:58 AM

What a logic :-)!!:-)!!:-). 0 where did you learn this attitude of making it very simple.

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#13

Re: Cable Copper Thickness

06/14/2010 3:45 AM

Dear Mr.Hithuanand,

I am following all the questions posted by you in this forum.

As one of the readers has pointed out you as EE !!, I still do not know why you

Torment OR torture us with your stupid questions. I am sure that some basic

qualifications is to be included in this forum so that people like you will not show

up OR pose as Qualified technocart or a Dumbfool.Sorry for my comments- it

is too harsh !.

Manroop Chennai.

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#15
In reply to #13

Re: Cable Copper Thickness

06/14/2010 5:17 AM

I am sorry i quit the forum but i was genuine with my intentions to know. I should learn first electrician job believe it i completed my graduation with full dedication.see you.

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Anonymous Poster
#16
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Re: Cable Copper Thickness

06/14/2010 2:19 PM

CR4 ADMIN: Deleted Post #16

Vulgar/Rude/Improper Behavior: This post was deleted because it did not adhere to the behavioral policies of the site. Please review Section 14 of the CR4 Site FAQ about rules for posting.

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Guru
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#17

Re: Cable Copper Thickness

06/15/2010 3:37 AM

→ British Standard 7671.

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Anonymous Poster (3); hithuanand (7); justinanto1987 (1); lyn (2); manroop (1); ozzb (1); PWSlack (1); redfred (2)

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