Feeding SMPS and other Electronics loads from Inverters 2

[Grollor33]

Hey all,

I understand all designs are a little different...I'm just looking for generic guidance....thanks a lot!!

I have a situation where I need to feed many (what of I'm guessing are)switch mode power supplies along with HMI displays, video cameras, various communication devices, etc. from power inverters/UPSs.

Power ranges from 5kVA to 250 kVA inverters...each with a mix of the "electronics" loads.

One of the main issues that has been raised is the startup of the system. My questions are for folks familiar with both (either) sides of the power system: Power Inverters & SMPSs

SMPS Question: What do these devices actually look like when they start up? Will they pull a slug of inrush current in order to charge up their input caps? If so, is it purely due to dV/dt on the cap? Is there a minimum voltage where the unit won't pull any current (during startup) and then "instantaneously" pull the starting current? Will the inrush be over within a cycle or two?

Inverter Question: We've spec'd the inverter to current limit to 2x its rating. Does anyone have experience in feeding these electronics' inrush currents? I'd like to think that I'm worrying about nothing and the regulation of the inverter will allow a cycle or two of high current to pass thus supplying the charging currents without placing the unit into a current limited state. Is this anywhere near the reality of what will happen?

There's also been worries of breaker coordination with a current limited source. Anyone have experience with feeding distribution circuits from power electronics components? Did you have the same nightmares that I'm having?

Thanks a lot.

 

[Skogsgurra]

Hello again,

This link is really interesting!

http://hightech.lbl.gov/dc-powering/

Sun, Intel and some other guys are moving (slowly, but still) over to DC distribution. I am very much in favour of that.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ScottyUK]

Biggest downside with DC is protection and switchgear - DC gear is minority interest and expensive. It does solve a lot of other problems though. Good link Gunnar.


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Sometimes I only open my mouth to swap feet...

 

[Skogsgurra]

The switchgear thing is being worked upon. Fuses have same breaking capacity on DC as they have on AC (Diazed fuses). Breakers will be semiconductor based. Wall outlets have been defined and standardized. Same cabling and isolation systems can be used. There are designs being tested already. I visited one such installation recently.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Madcow]

"A solution to this kind of problem might be a very neat - and very old - technology called DC."

We did one for Tandem computers(now HP) back in 1989,
350vdc bus. Distributed 350 was a pain from a saftey
point.

Rackable is doing alot of distributed 48vdc.

http://www.rackable.com/products/dcpower.htm

What site were you at Skogs?

 

[Skogsgurra]

It is called Elicom in Tibro, Sweden.

You are right about safety. But problems are there to be solved - I am actually doing a feasability study on a DC RCD that doesn't cost 500+ dollars - like the one used today.

I shall try find a picture of the paper article about that visit. I wasn't alone. There were five guys from (the) Japan telecom operator and NEDO (New Energy Development Organization) of Japan. Plus a university guy. This is real.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Sailboats are migrating to 'smart' DC distribution because the semiconductor fuse method is making it feasible. The breakers all get put on a communications bus and then they run as the switches and the protection. You can even program the protection value. Kinda clever.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Skogsgurra]

Found the article. It is in Swedish, so not very interesting for most of our visitors. But there's a picture showing the event. Me third from right. And, yes, the telecom company is NTT. I was wrong about the city. It is Toreboda, not Tibro. Close, but other city.

http://tinypic.com/view.php?pic=2eai9uc

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

I can't quite tell Skogs are you quietly picking all their pockets?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com