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Q: input/output-wattage of poe adapter Answered

hi, i found an ubiquiti poe adapter 100-240v .3a input. here the q: the output is 24v .5 amps >> shouldnt the input/output-wattage be about the same (not considering losses due to conversion, heat etc)? i am confused (but then: i´m usually always, haha)

bow.

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la xerra

15 days ago

alphaomega, wanted to take a photo of the poe-unit, but the label i so small that my cell-cam just fails. that said: not much data provided: just says i/p ac 100-240v 50-60hz .3 a, model ubi-poe-24-5, o/p dc 24v .5 a, i.t.e. power upply, +4,5pins ; -7,8pins

your example of 30w in and 12w out sounds outlandish, but given in which world we livedie in: aboyt right (total waste...gutfeeling tho is: efficeny a tick higher; i figure you chose the worst-case scenario)

no, havernt done any measurment yet - will do once chinachildlabor sends goods up here to the mountain. cheers.



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AlphaOmega1

18 days ago

The input current of 0.3A will be worse case @100V (Supposedly 30W)
This will dictate cabling and fusing requirements and so may be slightly over rated regarding the current to allow for multiple devices on a circuit.

The device output is limited to 24V at 0.5A (12W output maximum)

As you say the unit can get quite warm and must be able to dissipate heat even if covered, so allowance must be made for thermal dissipation. Is the device (case?) wattage displayed?

IIRC it's not unusual for switching regulators to be 98% efficient, lets say this one is, so we'd expect an input current after initial inrush etc. to be a little more than 0.12A at 100V assuming that the device is actually drawing 0.5A. TBH I'd take much of this with a large pinch of salt!

Have you measured the input current (using an AC ammeter), while checking the output voltage and current? It should all add up, but It may make interesting reading :)

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la xerra

19 days ago

i read online that dc-wattage = 75% to 90% of ac watts, typically - (being a virgin, that seems to be quite a waste; suck efficiency).

also: if the inside takes 100-240v, as stated on that thing, it burns .3 amp no matter what¿¿

and:
220v x .3 = 66w >>
24v x .5 = 12w >>
75% of 66 w = 49.5

so how do 12w vs 49.5 add up? ., ., ., ,. , thanks

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webcamsu

19 days ago

The adapter is switching and non-linear, and the AC power is not equal to the DC power.

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garzo

19 days ago

Also consider that 240V are AC while 24V are DC.