Cable selection for AC & DC application

http://cr4.globalspec.com/thread/22630/Cable-selection-for-AC-DC-application

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Can i use the same cable ampacity

Yes if you are meaning same RMS values

RMS=root mean square

So Square Idc=Square Irms ac.

And that is what dissipates inside cable-and heats up the cable isulation etc--the limiting criterion.

Thanks. I would like to elaborate my question. I am using standard cable ampacity table of a particular cable manufacturer for my use. This ampacity shown in the table is in which form AC or DC. Can i consider cable ampacity for a particular size of the cable irrelevent to the application i.e. AC or DC.

Let's say a cable manufacturer provides a cable ampacity table and according to it 2C X 16 sq. mm. copper cable ampacity in air is 115 amps. My question is can i consider same current for the AC or DC application? This 115 amps current is in which form?

I mean do we require to perform following equation to get the equivalent Idc value from the cable ampacity chart of a given cable of a given manufacturer

Idc = Iac x √s where

Idc = DC ampacity

Iac = AC ampacity at 50 Hz

s = Skin effect ratio at 50 Hz

The mfr would normally state the tested, true nominal amps capacity of the cable...they would naturally expect that - and feel most immunized against liability since - the cable will be derated to a specific application. Therefore, divide nominal cable amp carrying capacity by 0.707 RMS approximation factor to obtain capacity for AC application.

Hello friend,

I am not worried about the derating factor for the cable size as the same i have taken care as i stated earlier. I am concerned about the base current which i should consider for AC and DC application.