Power Supply Dealing with high amperage DC

[pavel]

Hi,

I've been thinking what to pick for a rather powerful system powered by DC-DC PSU? For the beginning, I look for 8700 + 1080 or new 2070, with a distant goal of making quad GPU platform for professionals.

What I quickly noticed is that amperage quickly get scary at higher end, even when going up to 48 volts.

Give it a chance to arc at such high current even for a second and it will certainly melt.

I think that popular connectors are not safe enough.

What connectors you can advice that have:

• Good resistance to arcing
• Minimum amount of contamination resistance (i.e. all contacts are protected from being touched by greasy fingers)
• Sane size for a consumer product
• Made from non combustible plastic. In case of worst case scenario happening.
• Has panel mountable version
• Has option for overmolding. Or even better, if it has existing cabling supply.

 

[Thehack]

Hi,

I've been thinking what to pick for a rather powerful system powered by DC-DC PSU? For the beginning, I look for 8700 + 1080 or new 2070, with a distant goal of making quad GPU platform for professionals.

What I quickly noticed is that amperage quickly get scary at higher end, even when going up to 48 volts.

Give it a chance to arc at such high current even for a second and it will certainly melt.

I think that popular connectors are not safe enough.

What connectors you can advice that have:

• Good resistance to arcing
• Minimum amount of contamination resistance (i.e. all contacts are protected from being touched by greasy fingers)
• Sane size for a consumer product
• Made from non combustible plastic. In case of worst case scenario happening.
• Has panel mountable version
• Has option for overmolding. Or even better, if it has existing cabling supply.

1. DC current is unlikely to arc. Arcing is when electricity travels through the air, and requires high voltage. 12-48V is not considered high voltage.

2. There is nothing wrong with exposed wiring. High current terminals are usually exposed, but have bulky connectors.

3. Most quality connectors are "non combustible."

4. The most economical high current connector are screw terminals/spade connectors. For a disconnectable but sane prices, you can use molex mega-fit which supports up to 23A. There are also "RC" bullet connectors that are very hardy and support high current.

 

[pavel]

About molex megafit. Aren't multi terminal connectors not safe for high current use? It is possible to vedge the connector in such position that only few of all pins will carry all of the current.

 

[Thehack]

About molex megafit. Aren't multi terminal connectors not safe for high current use? It is possible to vedge the connector in such position that only few of all pins will carry all of the current.

No.

If they are unsafe, why would reputable companies produce them and engineers use them?

 

[pavel]

No.

If they are unsafe, why would reputable companies produce them and engineers use them?

My understanding is that those connectors are not made for live disconnect, nor a lot of connection cycles, but for stuff that will have these connectors plugged or unplugged less than 100 times in a lifetime, and be used in more or less professional setting.

 

[Thehack]

My understanding is that those connectors are not made for live disconnect, nor a lot of connection cycles, but for stuff that will have these connectors plugged or unplugged less than 100 times in a lifetime, and be used in more or less professional setting.

Nothing is made for live disconnect except anti-spark (solid state relay) connectors.

I'm not sure where you're coming with these assumptions? What is your actual use case? Power entry? Blade style gpu set up? What is your background?

 

[pavel]

Nothing is made for live disconnect except anti-spark (solid state relay) connectors.

I'm not sure where you're coming with these assumptions? What is your actual use case? What is your background?

Yes, low sparking will be a better word. I know for sure that high current connectors do get eroded due live connects/disconnects that will inevitably happen in a consumer product, and surface contamination. Google is full of "XT90 melted" photos.

The actual case been described above: compact workstation class PC with external power brick (and sourcing high power ones is not a problem.)

My background, well it was just a boring business school program. I was on the route becoming a semiconductor engineer 10 years ago, but my parents nevertheless sent me studying "businessy things rich people do." A long story.

 

[Thehack]

Yes, low sparking will be a better word. I know for sure that high current connectors do get eroded due live connects/disconnects that will inevitably happen in a consumer product, and surface contamination. Google is full of "XT90 melted" photos.

The actual case been described above: compact workstation class PC with external power brick (and sourcing high power ones is not a problem.)

My background, well it was just a boring business school program. I was on the route becoming a semiconductor engineer 10 years ago, but my parents nevertheless sent me studying "businessy things rich people do." A long story.

Well then, yes obviously sparking (not arcing) is an issue that causes residue.

You should probably think about power connectors after you figure out your circuit specifications and how you are power the system.

This is like worrying about what bolt you're going to use before you've actually designed the table. Design the table first, then figure out what bolt you need.

You also made a quite a few assumptions without any technical knowledge. For example your comment about multi connectors not good for high current systems. Multi terminals provide redundancy for power, so that IF a terminal fails, it wouldn't overheat and just use the other terminal.

For your use case, you should actually define the parameters:

1. What component does it need to power? A computer is not an answer because you'll need a DC-DC solution if you are using atx based pcs. What actual AC-DC solution are you using?
2. What voltage?
3. What current?
4. What work place environment?
5. Does it need to be military style dummy proof?
6. Does it need to be weather resistant?
7. Does it need to be redundant?

But most of that, is determined after you've designed the system.

 

[pavel]

Well then, yes obviously sparking (not arcing) is an issue that causes residue.

For your use case, you should actually define the parameters:

1. What component does it need to power? A computer is not an answer because you'll need a DC-DC solution if you are using atx based pcs. What actual AC-DC solution are you using?
2. What voltage?
3. What current?
4. What work place environment?
5. Does it need to be military style dummy proof?
6. Does it need to be weather resistant?
7. Does it need to be redundant?

But most of that, is determined after you've designed the system.

1. For the first project - 8700 + 1080/2070, so about 350W with 500W worst case peaks. For AC-DC, I plan to use something like this https://www.alibaba.com/product-det...l?spm=a2700.7724838.2017115.23.3f48784fXAb4Ws . Criteria here is that it should have high enough switching frequency, and big caps to smooth peak currents. For DC-DC, I am looking to making one myself.
2. 24V, but I am tempted to go higher
3. 25A - should have some safety margin
4. Office use
5. Yes
6. Moderate resistance to fat fingers and schmoo
7. No

 

[Thehack]

The AC-DC unit you linked is internal. So you should use the screw terminals type.

There is no fat finger issue because you're not using an external AC-DC.

 

[pavel]

The AC-DC unit you linked is internal. So you should use the screw terminals type.

There is no fat finger issue because you're not using an external AC-DC.

That's not that important, getting a suitable AC-DC PSU is not a problem. A mall filled to the brim with every variety of them possible is just 4 km away.

 

[Thehack]

That's not that important, getting a suitable AC-DC PSU is not a problem. A mall filled to the brim with every variety of them possible is just 4 km away.

That is the point though.

Your AC-DC determines connectors you can use.

You should flesh out your designs and components before going back and determine which connector is right. Don't put the cart before the horse.

 

[pavel]

I found this - http://www.andersonpower.com/us/en/products/saf-d-grid/400-vdc.aspx seem to be providing a lot of overkill factor, along with all things I wanted. Existing cabling being the biggest one