voltagw drop
- Thread starter MBLES
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gar
Senior Member
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- Ann Arbor, Michigan
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- EE
130926-1041 EDT
Your question is not clear.
If you have a 100 A load 1000 ft from your source, 2000 ft of wire, and use 0000 copper and the wire is at 20 C, then the voltage drop is about 10 V. Because of self heating of the wire from the current this 10 V drop may be a good estimate for your 800 ft. A 10 V drop from 48 V puts your load at 38 V. This does not look good.
What is the 100 ft you mentioned.
You may need to consider a different way to get 48 V DC at your end point.
What is the load? Is this on continuously or just for short times? More information is needed.
.
Your question is not clear.
If you have a 100 A load 1000 ft from your source, 2000 ft of wire, and use 0000 copper and the wire is at 20 C, then the voltage drop is about 10 V. Because of self heating of the wire from the current this 10 V drop may be a good estimate for your 800 ft. A 10 V drop from 48 V puts your load at 38 V. This does not look good.
What is the 100 ft you mentioned.
You may need to consider a different way to get 48 V DC at your end point.
What is the load? Is this on continuously or just for short times? More information is needed.
.
ok I need to run for 48v dc @800' for 100a continuous load, 2- conductor copper in conduit. power supply has to be
-48v
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
130926-1128 EDT
MBLES:
What is the 100 A load? What is the lowest voltage it can operate at? How sensitive is the load to voltage variations? Can your input voltage be 58 V so that a 10 V drop would put 48 V at the load? If this was done would anything be hurt if under no load conditions there was 58 V at the load end?
Can you put your 48 V power supply at the load, and supply 480 V 60 Hz to the input of the power supply?
.
MBLES:
What is the 100 A load? What is the lowest voltage it can operate at? How sensitive is the load to voltage variations? Can your input voltage be 58 V so that a 10 V drop would put 48 V at the load? If this was done would anything be hurt if under no load conditions there was 58 V at the load end?
Can you put your 48 V power supply at the load, and supply 480 V 60 Hz to the input of the power supply?
.
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- Placerville, CA, USA
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- Retired PV System Designer
Is there any way that you can locate the DC supply closer to the load and run a 240 volt or 480 AC. line to it?
If nothing else, this would allow the 48V to be regulated even if there is a large drop in the AC side.
Last edited:
- Location
- Illinois
- Occupation
- retired electrician
The online calculator that I use shows a 5% drop at 100 amps and 800' using 750kcmil copper.
I know that some smaller DC power supplies have a "sense" connection. You run small conductors back from the load and connect to the sense input on the power supply. The power supply increases its output voltage to get the correct voltage at the load. Not sure if bigger power supplies have this feature.
Last edited:
kingpb
Senior Member
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- SE USA as far as you can go
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- Engineer, Registered
IMO - I think someone is looking for the answer to a test question.
Need more info to help you....what is the voltage drop requirement?
Need more info to help you....what is the voltage drop requirement?
MBLES- the wire size will be dependent on the voltage drop requirements. The customers we serve DC to have various voltage drop requirements: 0.5v, 0.75v, 1.0v. I notice some others here are using 5v, and some folks use % of the base voltage. I run at least two calculations for every wire; what formulae are you using? That might be a better starting point. It would also be helpful to know what kind of wire you plan to run....Chapter 9 Table 8 is for set number of strands/conductor. If you're planning to use fine-stranded wire, for example, their DC resistance/k-ft is different than the Chapter 9 Table 8 in the NEC. Also, copper or aluminum? k = constant for Cu or Aluminum, I = current (A), L= length (ft), cm = size in circular mils
Need more info to help you....what is the voltage drop requirement?
MBLES- the wire size will be dependent on the voltage drop requirements. The customers we serve DC to have various voltage drop requirements: 0.5v, 0.75v, 1.0v. I notice some others here are using 5v, and some folks use % of the base voltage. I run at least two calculations for every wire; what formulae are you using? That might be a better starting point. It would also be helpful to know what kind of wire you plan to run....Chapter 9 Table 8 is for set number of strands/conductor. If you're planning to use fine-stranded wire, for example, their DC resistance/k-ft is different than the Chapter 9 Table 8 in the NEC. Also, copper or aluminum? k = constant for Cu or Aluminum, I = current (A), L= length (ft), cm = size in circular mils
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