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Volts x Amperes = Watts

post #1 of 6
Thread Starter 
So we all know that Volts x Amperes = Watts but that doesn't seem to make sense

For example taking a Frotron 400watt PSU with +3.3V@22A, +5V@21A, +12V1@18A, and +12V2@16A

3.3v x 22= 73watts
5v x 21= 105watts
12v x 34= 408watts
total= 580watts

But that is way more than 400watts... Am I missing something here??? Is it just the max watts each rail can have but they really are lower and average out????

Also is the Froton good????
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post #2 of 6
they must just be counting the 12 v rail maybe, some PSU's will quote the maximum wattage across all voltages and say that it is 580 watts and some just the 12v rail, there is so many different power supplies and scams to get us to buy them its not funny.
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post #3 of 6
Quote:
Originally Posted by guitar22891
So we all know that Volts x Amperes = Watts but that doesn't seem to make sense

For example taking a Frotron 400watt PSU with +3.3V@22A, +5V@21A, +12V1@18A, and +12V2@16A

3.3v x 22= 73watts
5v x 21= 105watts
12v x 34= 408watts
total= 580watts

But that is way more than 400watts... Am I missing something here??? Is it just the max watts each rail can have but they really are lower and average out????

Also is the Froton good????
Forton is what I think you are talking about, and yes they are good reliable PSU. I think your problem has something to do with efficiency. I think the 400Watt advertisement is true because it can do 400 watts reliably, its overall power rating of 580 is probable at 100% efficiency which is impossible.
If your PSU is 75% effiecient then: 580 watts x .75 efficiency = 435 watts.
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post #4 of 6
Thread Starter 
Oh ok I see thanks......
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post #5 of 6
Thread Starter 
Oh another question what do these rails power... -12V@0.3A, +5VSB@2A on the froton.??
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post #6 of 6
metalman is absolutely correct. thats why even if u r buying a 1000watt psu, u must check for two very important things.

1. temperature it is rated at. it is common for the mfg to rate it at 15°C which is not correc since most ambient temperatures are higher than that. higher ambient temperatures mean ur effective power drops.

2. the efficiency rating. every psu manufacturer (electrical equipment mfg for that matters sake) MUST indicate clearly the efficiency and the power correction factor on the appliance. this efficiency rating determines your power consumption effciency. if for instance as above you have a 1000W PSU with an efficiency of 48% then you will arrive at 480W of power which would naturally double your electricity consumption. so u must check this too.
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