PSU > How Much Power!?i

Ice Rich

Ice Rich

Ice Rich

Soldato
Joined
3 Dec 2004
Posts
2,640
Hi all,

Am I right in saying that as long a PSU is relatively modern, it will only take/use the amount of power needed? For example, a 1000w PSU would use no more then a 200w PSU as long as the usage is the same?
 
Pretty much ALL PSU's will only supply the current that the load demands/requires.
As far as efficiency comes into it then your talking about power factor, inductive and capacitive reactance ..etc ..etc.
But yes modern PSU's are more efficient as they have active power factor correction which means it can alter the value of capacitor used to correct the power factor as the inductance will alter depending on the amount of current being drawn.
 
Green-Peace said:
Pretty much ALL PSU's will only supply the current that the load demands/requires.
As far as efficiency comes into it then your talking about power factor, inductive and capacitive reactance ..etc ..etc.
But yes modern PSU's are more efficient as they have active power factor correction which means it can alter the value of capacitor used to correct the power factor as the inductance will alter depending on the amount of current being drawn.
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Thanks for that :)

Whilst on topic, im using an extension lead (not for the extension but to give me more inputs), is it worth spending any extra on a quality extension unit? This may sound silly but could it handle the efficiency of electricity better?.
 
Sorry to bring up this post again but I've just ordered a 'Belkin Gold' 7way plug extension lead. It seems very good quality but is it ok to use all 7 of the outputs at same time? I.e speakers, pc, 360?
 
You've still got the limitation of the fuse in the plug at the end of the extension lead (i.e. up to 13A) but if all your devices use less than that it should be safe.
 
semi-pro waster said:
You've still got the limitation of the fuse in the plug at the end of the extension lead (i.e. up to 13A) but if all your devices use less than that it should be safe.
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I'll be honest and say my knowledge of electricity is minimal. So are you saying 13A is the maximum fuse you can get, and that all the devices on the extension (when in use), should not exceed 13?
 
semi-pro waster said:
Should be that or less but most will have a 3A fuse in them I think so it ought to be fine.
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Do you know if a fuse is like a PSU i,e it only takes the power it needs? Or is it always working at 3a? I feel a bit stupid for asking these questions as im sure its stuff all you guys know, but i really have not got a clue with electricity. Thanks
 
I'm not an electrical expert either but a fuse simply acts as a cut-off switch, when 3A (or whatever) is exceeded then the fuse blows and stops the current flowing because the circuit is broken. All that will be passed through a fuse is what is necessary plus a miniscule amount which will be lost due to the inevitable resistance of the wire itself (I think).
 
semi-pro waster said:
I'm not an electrical expert either but a fuse simply acts as a cut-off switch, when 3A (or whatever) is exceeded then the fuse blows and stops the current flowing because the circuit is broken. All that will be passed through a fuse is what is necessary plus a miniscule amount which will be lost due to the inevitable resistance of the wire itself (I think).
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I see, thanks. Is there a guide between the number of amps to use for a certain amount of wattage or are they not really connected? I.e would a 300w need mores amps then 600w?
 
You should be more than fine.

I run my 24" monitor, PC in sig, XBOX360, XBOX HDDVD drive, logitech Z-10's and a headphone amp off the same socket.

When you consider you can run storage heaters, washing machines and powerful hoovers off sockets a few lower powered items will not trip the fuse.

I'd be amazed if all the stuff i listed draws over 1kw when up and running.

I know for a fact that my PC idles at under 200 watts and gets to around 350 watts at full tilt.

gt
 
Seeing as mains should be 240 volts, I'll show you an easy way to work things out, for the question you have asked...

Watts divided by Volts = Amps

Hence:-

300W divided by 240V = 1.25A

600W divided by 240V = 2.5A
 
a psu will only use what it needs to to get the job done after factoring in a little loss due to heat ect. most modern psu's are >80% efficiant for the majority of their available output.

fuses limit the current a device can pull. they are there to limit the device in such a situation that there is a problem and the device pulls too much current which could damage it and/or other things plugged in. the fuse is there to stop that from happening.

13a is biggest fuse you'll see on a domestic mains circuit as that is the largest amount a device is allowed to safely pull from a 3 pin plugl (3120 watts, 240v x 13a).


i (well, my electrician friend) just put my electric oven in a few days ago (on its own breaker before anybody asks lol). it's rated to pulls 10450w from cold with everything up full. yes, ten thousand four hundred and fifty watts lol. thats 43.5 amps. i can see that increasing my electric bill just a little bit lol :p the manual recommended we use 6mm twin and earth but we took no chances and went with the 10mm stuff. its some manly cable alright lol
 
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If you want to turn the equation around to see how many watts you can put through a fuse then:-

Volts x Amps = Watts

Hence:-

240V x 3A = 720W

240V x 5A = 1200W

240V x 13A = 3120W
 
That's one scary cooker!


One other thing, the idea that the number of devices matters is a dangerous old wive's tale. We used to run out stage rig, some 30+ devices, from a single plug, and no problems at all, as total consumption was less that 1000W.
But, plug 2 electric fires into the same socket, and boom boom.


The only other thing nobody's mentioned is that with extension leads, if you ARE running something hefy on them, you should not leave it on the cable drum or in coils on the ground. These will create electromagnetic interference and potentially a great deal of heat.
 
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