Transfer 24 VDC to 1000 ft...

Reloadron

Joined Jan 15, 2015
5,788
Would it be possible to run mains voltage to your location and then use a SMPS to get your 24 volt supply? That would make for much easier than running 24 VDC down a 1,000 foot run. There would also be a smaller I*R drop.

Ron
 

Thread Starter

maitrey

Joined Sep 4, 2014
72
Would it be possible to run mains voltage to your location and then use a SMPS to get your 24 volt supply? That would make for much easier than running 24 VDC down a 1,000 foot run. There would also be a smaller I*R drop.

Ron
All 21 devices are installed in various locations in clean rooms! They probably don't wanna have any active electrical components in clean room! :(
 

Thread Starter

maitrey

Joined Sep 4, 2014
72
That is what it sounds like, unless you are only supplying the input signal.
I am not supplying input signal from my SMPS.

This might be a stupid question. But, what happens if I select this SMPS (https://www.alliedelec.com/product/siemens/6ep15363aa00/70385086/) and only provide power supply to one device which requieres 24 VDC/ 2.70 amp? Will it explode or only take 2.70 amp?

P.S I am thinking about dividing power supply to three phases (3x 20A each to compensate for 56.7 amp requirement).
 

Papabravo

Joined Feb 24, 2006
15,134
Correct. My bad. Thanks for clearing this!

The device requiers 24 VDC power supply and its total power consumption is 65 Watts max. (This is too much for an actuator!)
Does it mean that each device requiers 24 VDC/ 2.70 A? And If I have 5A coming from SMPS then it won't be sufficient??
I think that is the inevitable conclusion. I think you might want to reframe the problem to provide an outside source of AC and put a power supply at each device. We still have other issues but you need to solve this one first. This is why AC power distribution won the 19th century battle for what system we would use for residential and commercial power.
 

Reloadron

Joined Jan 15, 2015
5,788
All 21 devices are installed in various locations in clean rooms! They probably don't wanna have any active electrical components in clean room! :(
OK, so you have 21 devices each requiring 24 VDC @ 65 watts or let's just call it 3 Amps per device so you are looking at over 60 Amps with the last load at the end of 1,000 foot of cable. Even running AWG 10 cable which is expensive and heavy you are looking at about 2.0 Ohms round trip so the voltage drop would be much greater than what you started with. Granted the full 60 amps is not at end of line but your I*R loss will be beyond anything close to reasonable. We won't even get into the signal line as that is likely not the biggest challenge. Clean rooms have classifications and most constantly monitor particle count using electronics. Most clean rooms I have seen have all sorts of electronics in them. I can tell you this, based on the data you have provided. You are not going to run 24 VDC down a line feeding 3 amp stations along 1000 feet of cabling. The way it would be done is run mains voltage and each of 20 stations has its own 24 VDC supply. Beyond that I simply do not see a feasible way to go about this?

Ron
 

Thread Starter

maitrey

Joined Sep 4, 2014
72
OK, so you have 21 devices each requiring 24 VDC @ 65 watts or let's just call it 3 Amps per device so you are looking at over 60 Amps with the last load at the end of 1,000 foot of cable. Even running AWG 10 cable which is expensive and heavy you are looking at about 2.0 Ohms round trip so the voltage drop would be much greater than what you started with. Granted the full 60 amps is not at end of line but your I*R loss will be beyond anything close to reasonable. We won't even get into the signal line as that is likely not the biggest challenge. Clean rooms have classifications and most constantly monitor particle count using electronics. Most clean rooms I have seen have all sorts of electronics in them. I can tell you this, based on the data you have provided. You are not going to run 24 VDC down a line feeding 3 amp stations along 1000 feet of cabling. The way it would be done is run mains voltage and each of 20 stations has its own 24 VDC supply. Beyond that I simply do not see a feasible way to go about this?

Ron
Agree. Running wire to 1000ft just doesn't seem practical. Is it same scenario for running AC voltage to the same distance?

What if the average distance be reduced to 150 ft? Does it make any better? Thanks,
 

Reloadron

Joined Jan 15, 2015
5,788
Agree. Running wire to 1000ft just doesn't seem practical. Is it same scenario for running AC voltage to the same distance?

What if the average distance be reduced to 150 ft? Does it make any better? Thanks,
Here is how it will always play out. The game has rules we need to follow. Wire, all wire has resistivity or resistance. There are formulas we can use to calculate the resistance of for example solid core copper wire. Here is an example of a chart. Using AWG 12 wire as an example the resistance would be 1.588 Ohms. That is One Way single conductor. Round trip we get a Resistance total of about 3.17 Ohms. Now here is the nice part of having the higher voltage. A 24 VDC 5 Amp rated supply has a primary side, just as an example 24 Volts at 5 Amps = 24 * 5 = 120 Watts. Let's call your loads a maximum of 3.0 Amps. So 24 * 3 = 72 Watts. That is the power and that 72 Watts at 120 Volts = 0.6 Amp. So now you have 21 stations let's say at 0.6 amp each or a total of 12.6 Amps. Even using AWG 10 wire the drop would be about 26 volts getting down around 94 volts but most SMPS power supplies run find down to 90 VAC in. Granted this assumes the load at the end of line. WE take the wire resistance times the current to get the voltage drop.

Yes, the shorter the run (distance) the lower the I*R drop of the wire. Matter of fact, in my example, with a 150 foot run, same load(s) the total drop would be about 3.9 Volts.

This is why higher voltages are chosen for long transmission runs.

Ron
 
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