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Single Multi Core Cable

01/28/2014 3:34 AM

what will be effect on system if 110v ac and 110v dc cables will run in same multo core conductor. is it possible???

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#1

Re: Single multi core cable

01/28/2014 5:45 AM

NEC 300.2 Limitations

C) Conductors of Different Systems.

(1) 600 Volts, Nominal, or Less. Conductors of ac and dc

circuits, rated 600 volts, nominal, or less, shall be permitted

to occupy the same equipment wiring enclosure, cable, or

raceway. All conductors shall have an insulation rating

equal to at least the maximum circuit voltage applied to any

conductor within the enclosure, cable, or raceway.

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#2
In reply to #1

Re: Single multi core cable

01/28/2014 5:59 AM

I have not understand what you mean.

But as per my question, for e.g. I have considered 2.5 Sq.mm X 10 c cable. 5Core used for A.C supply & other remaining 5 core for D.C. core so is there any effect come because of different voltage???

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#3
In reply to #2

Re: Single multi core cable

01/28/2014 7:29 AM

What different voltage? 110 = 110.

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#4
In reply to #2

Re: Single multi core cable

01/28/2014 8:08 AM

No.

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#6
In reply to #2

Re: Single multi core cable

01/28/2014 8:31 AM

Yes! The cores which carry the AC current, will have a varying magnetic field set up around them. The stray flux from this alternating magnetic field, would induce stray emf in the cores carrying DC current. As the DC cores too have a closed path, this induced stray emf would circulate a current thro the cores of the DC voltage, which would add or subtract with the current already flowing in these cores. Also, there could be additional heating in these cores because of the induced current.

Thus, it is not a good practice to run AC & DC voltage wires in the same multi core cable.

If the individual cores or pairs (in paired cables) are having individual shields/screens, which could be earthed, then there would be no issue.

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#9
In reply to #6

Re: Single multi core cable

01/28/2014 10:22 AM

You are also correct. But allow me to break down the critical points here for the OP.

  • A multi-core cable can carry AC and DC signals signals if one does not exceed the insulation voltage rating.
  • The local wiring standards are the authority the OP should consult to see if this is permitted, NOT CR4 or any other public forum.
  • The close proximity of AC and DC voltages will always interfere or couple with each other. Insulation reduces coupling, it does not completely stop it. This may cause unwanted effects on the load from random responses to the release of inherent smoke of a device. Most likely it will not make a difference.
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#5
In reply to #1

Re: Single multi core cable

01/28/2014 8:25 AM

Dear Sir, your NEC 300 of US of A does not apply to India, from where I suppose the OP hails.

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#12
In reply to #5

Re: Single multi core cable

01/28/2014 5:24 PM

We got lots of Patel's 'round here in Tennessee, USA .

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#13
In reply to #12

Re: Single multi core cable

01/28/2014 6:01 PM

Not just in Tenn.

"A Patel Motel Cartel"

"Wherever there is a motel in the United States, there are likely to be people from India running it." <Paraphrased>

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#16
In reply to #13

Re: Single multi core cable

01/28/2014 10:26 PM

In my area, the last time they printed a phone book there were more Patel's than there were Smith's listed in it.

Simply a statement of numerical fact.

Good Luck, Old Salt

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#17
In reply to #16

Re: Single multi core cable

01/28/2014 10:40 PM

You counted both of them and compared.

Sounds like either losing a bar bet or a very boring night.

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#18
In reply to #17

Re: Single multi core cable

01/28/2014 10:51 PM

Or, a very small phone book with lots of Olsons, Hansons, Johnsons, Petersons, etc. mixed in with the newcomers.

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#8
In reply to #1

Re: Single multi core cable

01/28/2014 10:06 AM

GA

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#10
In reply to #8

Re: Single multi core cable

01/28/2014 11:08 AM

Thanks, redfred!

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#7

Re: Single Multi Core Cable

01/28/2014 9:39 AM

Theoretically, what electricalexpert65 said is correct. But practically if the conductor insulation is as per IEC 60502-1 for 20 A a.c. current only 1.6 V will be the a.c. emf induced in dc. circuit for 1 km cable length. Usually for 100 m[330 ft] length and 10 A the emf will be 0.08 V.

IMO if NEC permits this it is no reason to avoid it.

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#11

Re: Single Multi Core Cable

01/28/2014 11:43 AM

Generally speaking specialty cables such as this one are used to provide signal and power to a specific piece of equipment, hence the mixing of the two signal types. In such cases the equipment is usually designed with signal conditioning components/circuits to mitigate the effects of electrical transients/noise/mutual coupling on the cables/signals. As long as the local codes allow such cabling there should be no problem.

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#14

Re: Single Multi Core Cable

01/28/2014 6:32 PM

The matter of needing mulltiple circuit isolations to make the cable dead needs to be considered, if not from a code standpoint then from a personnel safety perspective. If one isolates a circuit running down a cable, is one entitled to assume that the whole of the cable is dead (rhetorical question - NNTR)?

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#15

Re: Single Multi Core Cable

01/28/2014 6:46 PM

You can see for yourself how much power is transferred from an AC connected line by measuring the voltage and current on the unconnected lines. when you measure it you can hook up a fast start motor and other loads and turn them off and on to see how much power transfer takes place.

If you have access to an oscilloscope, even better. What you will see is that if your 110 VDC is continuous and steady 110 volts without any increase or decrease, the induced EMF will alter your smooth DC feed.

Then you need to ask yourself, "Can the electronics handle this ripple or will it damage or shorten the life of the DC connected components?"

Sometimes the answer is hard to see if the manufacturer does not adhere to any manufacturing standards and uses lower capacity parts to sell for cheap and get return business when the item fails.

Also, your power quality feeding into the place you are working on may also be poor quality and cause electronics to fail sooner. You can take some time to study rectifiers, filters, surge protectors, and any other form of signal conditioning to have a better grasp of what is at stake.

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Users who posted comments:

7anoter4 (3); Amar Patel (1); bigg (1); electricalexpert65 (2); garyrich2000 (1); lyn (3); old salt (1); PWSlack (1); RAMConsult (1); redfred (3); Tornado (1)

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