configuring 3 power supplies in parallel

[Procto]

Hello. I am working on a communications project that will increase the current to handle the wattage output for this transceiver. I am wanting to know if the 2 wiring diagrams provided will produce the same outcome. Each power supply is 13.8v and 30a. The desired amperage is 90. 1 additional question is, what if 1 of the power supplies was say, 20 amps? Would the end result be 80a? Thanks.

 

[davenn]

your 2 drawings are the same configuration, just drawn differently
dunno if that is what you intended ??

overall, this is a really, really bad idea, its isn't wise to parallel PSU's
This is because if they are exactly and utterly identical ( and I don't mean in make and model)
one PSU is always likely to be working harder and if pushed too much for too long, it will fail and this will lead
to a chain reaction of failures of the other supplies as they try and pick up the load but cannot do so

what sort of transceiver are u using that requires 90A !! ?

you are much better off with a single supply rated at least, in this case, 10A capability higher than what you need


Dave

 

[73's de Edd]

Sir Procto . . . . . . .

Pray tell us . . . . WHAT transmitter do you have that operates, using an INEFFICIENT 12VDC voltage level at that FIERCE of an amperage ?

Both of your drawings seem the same, only with your improvement and learning curve being enhanced on the seconds better layout and its color coding.

Re:



I could only see the use of isolation / steering diodes on each supplys power output lines.
That separates the supplys from each other and that odd 20 amp supply could add in its output . . . . . isolated.
Each one doesn't care about the other . . . .they all just have to respond to supply, when that demand is made.
Should you opt for the diodes below a set of four 15 amp units would distribute the current loading between them.
The voltage spec is about the highest available in a Schottky diode and the lower doltage drop across each one of them.
It is also gonna conserve the most of that initial 13.8V, in the resultant voltage drop across them on EACH power supply leg..
Unless they happen to be adjustable, so that you could set the voltage output up just enough to make up for the diode voltage drop.
You can pay an arm and a leg for some metal cased units and even the TO-220 and TO-3 cased units are pricey.

Check out something like this:

http://www.ebay.com/itm/20-PCS-15A-...R-RECTIFIER-for-solar-panel-DIY-/271961586414

Thassssit . . . . .


73's de Edd

 

[Procto]

Hello again. Thanks for the replies. I am told by the manufacturer of SUPERNIGHT and POWERMAX that the power supplies can be run in parallel. All of the answers I am seeing on forums and around the web say as you are, do not do this! What are these guys doing that is so bad or are they doing some tricks we can't see?

This link is the 30amp power supply I have. http://www.amazon.com/SUPERNIGHT-Switching-Power-Supply-Strip/dp/B007MWNF5Q

I also have 2x 100amp power supplies POWERMAX-PM3-100-CONVERTER-CHARGER-AUTOMATIC. I have a HF amp that will pull 80amps continuous and 180 peak. I plan to parallel the 2 PM3-100s for that setup.

I also have a ridiculous car stereo (2200 watts) and we go to shows. Sometimes they are indoors and running engines indoors might put everyone to sleep/death so being able to run your gear from a power supply is very nice.

This guy is doing at 200amps with 4 50a supplies.

300 amp power supply from parallel supplies.

 

[73's de Edd]

Sir Procto . . . . . . .

What are these guys doing that is so bad or are they doing some tricks we can't see?

I consider that they are incorporating that circuitry that I have shown . . . . .as being built into their supply.
It does sort of make a power supply " goof proof" on hook up, by the end user.
Plus I see by your last reference, that the supplies do offer a wee bit of + voltage adjustment.

73's de Edd

 

[BobK]

Using diodes to share the current is not the best way. If you are going to do so, resistors work better. Why? Because a resistor will respond linearly to drop the voltage based on current whereas the diode responds logarithmically. Thus the resistors adjust down the voltage of the highest voltage supply with a smaller change in current than the diodes would.

Bob

 

[Procto]

I can adjust the voltage on them and I've seen 1 video that says to make 1 just a little lower than the other.

.

It seems that if you do this you will have one working at 100% and the other maybe 50% or whatever 80% depending on the load?? Wouldn't that burn out the supply being worked at 100% all the time? I can get them to be the same voltage with my meter and adjusting the voltage a little bit.

Powermax said to me in an email that I wouldn't need to adjust the Pm3-100's at all. One runs at 13.2, 13.8 14.6 and the other slightly older model runs at 13.75v. Both are 100a.

How many of the SCHOTTKY BARRIER RECTIFIER's would I need to connect to each positive pole and is this the preferred way to prevent burning down my house? It looks like they would need to be put in parallel also? Thanks for the replies and helpful information.

 

[davenn]

It seems that if you do this you will have one working at 100% and the other maybe 50% or whatever 80% depending on the load?? Wouldn't that burn out the supply being worked at 100% all the time?

That's what I was saying a few posts ago and why it's generally a bad idea