How to calculate current carrying capacity?

you know V=I*R that's ohm's law you want to know the value of I that is current so you should know V and R let us suppose V=220(volts) R=1(Ohm) then I (current)=220 but these are ampere remember about units. so if want to calculate the amount of current you should know the voltage and also the resistance so go to the dealer and ask him about the resistance of conductor.But don't for get that they may cheat you to sell low standard conductors. But here is another choice you may ask the dealer about Cable Size Data Book this will be helpful as it has your required information.

Please refer to tables available for various diameters of copper and aluminum cables, in web. http://www.sbeecables.com/docs/single_core_&_multicore_flexible_cables.pdf I quote: All wires have a small amount of resistance and this causes them to heat up when carrying current. The wires are quite happy to get red hot but their covers and things around them might not like it. Finally the wire can melt if it gets hot enough. Most manufactures will specify the current a wire can carry. If you are an electrician you will have a whole book about the standards of what currents certain types of wires are allowed to carry. One of the odd things to consider is not how much current is carried during standard operation, but how much current might be carried if a fault occurs. This is another method of choosing wires in some cases (if they happen to lie in the fault path). You can try http://www.powerstream.com/Wire_Size.htm%E2%80%A6 http://circuitcalculator.com/wordpress/2%E2%80%A6 , http://www.alphawire.com/PAGES/383.cfm and so on. If you have an electrical engineering book, it may have formulas or tables that show you what wire you should use. Source(s): electrical engineering books and the links I have given above are good references.

The current density of a single wire is expressed as amps per sq mm. For copper busbars, you may use 1000 amps per sq inch. This cannnot be applied to multi core cable. (There are NO straight formulae if you are asking about cables. And also In any conductor, the current does not flow in the center of the conductor.) if the cable core is made of say 7 strands, the heat from the inner wire spreads to the outer wires, making it to apply a derating factor for this cable even though individually each core can handle larger current.. Excess heat damages the insulation and finally the cable fails. The larger the current or cableable, the larger is the derating. Each cable manufaturer specifies current rating of their cable to certain conditions. I use 0.8 derating factor to manufacturer ratings. When you parallel more cables, the derating is higher since the canles never share current equally. You can see this obviously with aluminum cables. Even for same cable, the current rating depends on ambient temperature, how cables are laid etc, Now for another type of conductor. For motors, depending on the insulation class A-E-B-F, the current density vary from 2.5 amps per sq mm to 6 amps per sq mm. For higher current density you have to use special insulation enamel that can withstand more temperature.

I'll assume that your are not concerned about the effect of the IR drop on the rest of the circuit, but simply how much current the wire can handle. It turns out that this is really a thermal problem. The reason it that the power loss causes heating of the wire which in turn heats up the insulation. The life of insulation is highly dependent on temperature and it varies for different types of insulation. Now to complicate the problem, the temperature rise of the wire (and insulation) depends on the physical placement of the wire. Is it in a bundle, a conduit, free space, etc.? This is a very complex problem, because of all the variables involved, and you would be better off using published wire rating tables.

The current density of a single wire is expressed as amps per sq mm. For copper busbars, you may use 1000 amps per sq inch. This cannnot be applied to multi core cable. (There are NO straight formulae if you are asking about cables. And also In any conductor, the current does not flow in the center of the conductor.) if the cable core is made of say 7 strands, the heat from the inner wire spreads to the outer wires, making it to apply a derating factor for this cable even though individually each core can handle larger current.. Excess heat damages the insulation and finally the cable fails. The larger the current or cableable, the larger is the derating. Each cable manufaturer specifies current rating of their cable to certain conditions. I use 0.8 derating factor to manufacturer ratings. When you parallel more cables, the derating is higher since the canles never share current equally. You can see this obviously with aluminum cables. Even for same cable, the current rating depends on ambient temperature, how cables are laid etc, Now for another type of conductor. For motors, depending on the insulation class A-E-B-F, the current density vary from 2.5 amps per sq mm to 6 amps per sq mm. For higher current density you have to use special insulation enamel that can withstand more temperature.

you know V=I*R that's ohm's law you want to know the value of I that is current so you should know V and R let us suppose V=220(volts) R=1(Ohm) then I (current)=220 but these are ampere remember about units. so if want to calculate the amount of current you should know the voltage and also the resistance so go to the dealer and ask him about the resistance of conductor.But don't for get that they may cheat you to sell low standard conductors. But here is another choice you may ask the dealer about Cable Size Data Book this will be helpful as it has your required information.