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Plug & Jack
pmowry:
Thanks for the thread ;) I bought a Schurter DD11 Series plug to put on the back of my cabinet before I thought about the current drawn. It 's rated for 7 amps. So from this thread it sound like I'll be ok. I'll solder a powerstrip to it this weekend and see what happens.
MonMotha:
FWIW, most PC supplies are ~75-85% efficient at mid-load and ~60-75% efficient at full load. It's pretty pathetic. There's an "80+" initiative that you can look for the logo on the box of a supply. That, in theory, means that the supply is at least 80% efficient at near full load. Some of these can top 90% at mid-load. Remember that if you don't have it fully loaded, it won't draw the nameplate current. It'll just draw what it needs to power the PC plus any losses in the PSU.
The nameplate logo usually does NOT include any inrush, believe it or not. Inrush on most cheap PC supplies can be on the order of 50-100A (no kidding!). It's just short enough to not trip your breaker.
I generally would not recommend actually running a PC supply at more than 80% of its stated capacity. They're usually just not actually designed for it. Most cheapies aren't even capable of much more than 60% of stated output capacity for more than a few minutes. Some REALLY cheap supplies are even rated in INPUT, not output, meaning that the "850W" rating means that you can (maybe) safely pull 850W from the wall, not deliver it to the load. Fortunately, most PCs don't actually need more than ~250-300W of DC power. People have been conditioned to buy really big PC supplies due to this overrating activity that goes on.
As for wall voltage, it does vary. Most places I've checked in the USA run between 115-120V circuit unloaded, which is generally accepted as the norm in the USA. I have a friend who's house runs a little high at ~123V, and some older dwellings are at more like 110V. USA wall voltage is "supposed" to be 120V but can be as high as 125V. 100V is considered very low in the USA, but Japan still runs 100V for some reason. If your wall voltage is 100V, you should have the power company turn it up some; they can do that. Europe has standardized on 230, IIRC. The rest of the world just picks something - usually 220-240V or 110-120V, and it's usually a "nice" number, but there is of course local variability which includes not just what the power company actually delivers but how loaded the circuit is.
Ed_McCarron:
--- Quote from: MonMotha on December 08, 2009, 05:34:21 pm ---Inrush on most cheap PC supplies can be on the order of 50-100A (no kidding!). It's just short enough to not trip your breaker.
--- End quote ---
Wow. No ---steaming pile of meadow muffin---.
protokatie:
--- Quote from: Ed_McCarron on December 08, 2009, 07:45:25 pm ---
--- Quote from: MonMotha on December 08, 2009, 05:34:21 pm ---Inrush on most cheap PC supplies can be on the order of 50-100A (no kidding!). It's just short enough to not trip your breaker.
--- End quote ---
Wow. No ---steaming pile of meadow muffin---.
--- End quote ---
I knew it was bad, but never figured it could be that bad, so I had a looksee on wikipedia and found this:
--- Quote ---When a transformer is first energized a transient current up to 10 to 50 times larger than the rated transformer current can flow for several cycles. This happens when the primary winding is connected around the zero-crossing of the primary voltage. For large transformers, inrush current can last for several seconds. Toroid transformers can have up to 80 times larger inrush, because the remnant magnetism is nearly as high as the saturation magnetism at the "knee" of the hysteresis loop. This is caused because the transformer will always have some residual flux density and when the transformer is re-energized the incoming flux will add to the already existing flux which will cause the transformer to move into saturation. Then only the resistance of the primary side windings and the power line are limiting the current.
--- End quote ---
TEN to FIFTY TIMES!!! :o
MonMotha:
Actually, PC power supplies don't have 60Hz transformers in them. Most of the inrush goes to charging up the bulk ripple filter caps on the output of the bridge rectifier. An NTC component is often used to limit this, but cheap designs won't have that (I'm not seeing one on a 430W Antec I've got disassembled next to me), and they only limit the inrush so much.
So yeah, no ---steaming pile of meadow muffin--- :) The transient is pretty quick though (on the order of a few dozen msec). You'd probably even have trouble catching it with an analog multimeter. The quickness is why it won't trip your breaker, but why your lights dim a little bit (if you watch carefully) when you first plug in your PC supply.
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