dc amps vs ac amps

[Lee Roberts]

I was told:

DC Amps and AC amps are the exact same thing, they are the measurement of electrons past a given point, the difference is that the electrons of AC go back and forth (alternating) and DC go only in one direction (direct).

Measurement must however be done with two different meters, if you measure AC with a DC ammeter it will twitch a lot but you'll get no reading, if you measure DC with an AC ammeter it might just let it's magic blue smoke loose and you will have a nice christmas tree ornament but no more ammeter.

So after comparing a few other sources on the differences between, AC and DC i'm happy that the above is true.

The reson for my original question regarding amps was because i am currently selecting the correct wire to use as supply lines to each of my driver cards. To futher explain that, i was already aware that diffrent gauges of wire would also draw current and if that is the case i needed to also ask the original question above.

Hopefully this post will also help somone else in the future, who may be looking for the same answer!

What i would like to know now is, how do we determine when a wire will start to draw current?

The reson i'm asking this question is because when i had my out building wired by an electrishion, he told me that you can't use over rated cable because it would draw, build up, demand current itself. So if thats the case really to do the job right i need to make sure that the wire i use to supply each driver, isnt going to do the above.

Maybe you guys could help me with this, am i going "way overboard" for what my circuit will be doing? or is this a good show of consistency in doing the job right.

What i'm basically getting at is this, my PSU is currently supplying my circuit with 38VDC @ 14a. Each of my driver cards are rated @ 4.2a (RMS 3A) MAX, so we know that the driver cards combined could require 12.6a (4.2 x 3 = 12.6).

The wire i have decided to use is rated @ 15a, so 15 - 12.6 = 2.4. So my wire should handle what is being requested in ampage but will the wire pull a little more current from the PSU as its rated @ 15a and a little over what the peak will be, going back to what i said above about wire and the (draw, build up, demand) ?

Now moving onto fuse's to protect my driver cards, i understand it that fuse selection is done so by adding 25% to the peak rating. So 4.2 + 25% = 5.25, so i would need to use a 5.25a fuse to protect each driver but actually a 5a fuse is the closest i can find so thats what i will be using? and if its true that the wire will (draw, build up, demand) do i need to take this into consideration on my fuse selection.