Volt drop and load

[Jamie Crutchley]

Hi. I am new to the forum and most of my experience is in 12/24v systems. I have a bit of a basic question really and was hoping to clear it up. If I had one PSU with an output voltage of exactly 12 volts and 4 loads of 1 amp each and a 5th load of 2 amps all ran in 1 mm cable and each cable run 20m would the voltage be lower at the equipment pulling 2 amps? Or would that equipment just drag down the source voltage as a whole? So basically doe's more current being drawn down a cable cause it to lose voltage through the cable or just at the PSU? I no the PSU voltage will drop the more load that is drawn but I'm not 100 percent sure if the load and CSA of the cable are related to each other as well. Obviously the CSA will make a difference to the overall voltage but will it be a bigger difference on the 2 amp load compared to the 1 amp load? Thanks for taking to help me out.

 

[shanky887614]

Hi. I am new to the forum and most of my experience is in 12/24v systems. I have a bit of a basic question really and was hoping to clear it up. If I had one PSU with an output voltage of exactly 12 volts and 4 loads of 1 amp each and a 5th load of 2 amps all ran in 1 mm cable and each cable run 20m would the voltage be lower at the equipment pulling 2 amps? Or would that equipment just drag down the source voltage as a whole? So basically doe's more current being drawn down a cable cause it to lose voltage through the cable or just at the PSU? I no the PSU voltage will drop the more load that is drawn but I'm not 100 percent sure if the load and CSA of the cable are related to each other as well. Obviously the CSA will make a difference to the overall voltage but will it be a bigger difference on the 2 amp load compared to the 1 amp load? Thanks for taking to help me out.

Shouldn't really get much volt drop on that size cable over such a short distance, last time really used 1mm belden was on a 100m run

 

[Jamie Crutchley]

Hi thanks for your reply. Sorry my example was a bad one. I know you will get no meaningful volt drop over that distance and cable but I just meant it as a hypothetical question. So to make it more realistic change the distance to 100 metres and the CSA to .5mm. Thanks again

 

[Knobhead]

If you use standard VD calcs, 20m of 1mm² @1A isn’t big enough. Depends what % the equipment will tolerate.

 

[Hawkmoon]

Hi. I am new to the forum and most of my experience is in 12/24v systems. I have a bit of a basic question really and was hoping to clear it up. If I had one PSU with an output voltage of exactly 12 volts and 4 loads of 1 amp each and a 5th load of 2 amps all ran in 1 mm cable and each cable run 20m would the voltage be lower at the equipment pulling 2 amps? Or would that equipment just drag down the source voltage as a whole? So basically doe's more current being drawn down a cable cause it to lose voltage through the cable or just at the PSU? I no the PSU voltage will drop the more load that is drawn but I'm not 100 percent sure if the load and CSA of the cable are related to each other as well. Obviously the CSA will make a difference to the overall voltage but will it be a bigger difference on the 2 amp load compared to the 1 amp load? Thanks for taking to help me out.

Yes, volt drop in the cable will be dependent on resistance/current in the cable (apply ohms law to the cable itself) - VD will increase proportionally with I
The PSU voltage will be effected by the combined load, not just one particular circuit