Power Consumtion

Unanswered Question
Jul 16th, 2009

Hi All,

I need to find 2 things a) the current power consumption of a range of different devices (3500,3560,4500...) b) potential max power consumption. I obtain the following output:

Power Summary Maximum

(in Watts) Used Available

---------------------- ---- ---------

System Power (12V) 411 1813

Inline Power (-50V) 0 2089

Backplane Power (3.3V) 0 0

---------------------- ---- ---------

Total 411 (not to exceed Total Maximum Available = 2500)

System Efficiency = 75%, 411 W drawn from power supply to provide 308 W

Inline Efficiency = 96%, 0 W drawn from power supply to provide 0 W

I understand that inline power is irrelevent as POE is not concerning me. My question is, what does this out put tell? am I drawing 411W from a potential 1813W? is this including both PSU's? why is system power only 12V when I have -48v DC going into the device?

HELP! thanks again for the great answers as always!

Matt.

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Giuseppe Larosa Fri, 07/17/2009 - 10:57

Hello Matt,

you provide -48 VDC to power supplies.

Power supplies provide stabilised voltages at convenient positive voltage levels (in comparison to ground) for different electronic parts.

The 12V is still too much for some modern chips so you can imagine there are where needed ways to provide a stable lower voltage.

in case of bigger devices multiple voltages are provided.

the system drains 411W to provide effective 308W and this can be expressed as efficiency.

The difference is the power / energy consumed in the operation of voltage stabilization and transformation (changing levels) inside the power supply itself.

Hope to help

Giuseppe

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