Power Consumption

[T.C]

Maybe the fluorescent tubes are rated in terms of their equivalent light output. For example, I am looking at a 60W (equivalent) compact fluorescent which produces 900 lumens and uses only 14W.

And perhaps the 20W ballast is rated in terms of actual power delivered. Then it would serve two 40W tubes. Don't quote me on these numbers, I am just guessing at the moment.

Yes, the ballast will dissipate some power, but I don't know how much.

that is another valid point, but the picture does not appear to represent flourescent tubes. also, we have not yet studied any sort of calculations based on relative lumen output. this is supposed to be simply the circuit calculations based on the rules of series and/or parallel circuits
let me see if I can repost the picture with the whole page

 

[nakulak]

It maybe that the ballast consumes 20 watts, while putting out 100 watts.

I'm thinking that this might violate the first law of thermodynamics ? (but not necessarily the NEC :grin: )

case 1: (I'm guessing ) that the calculation should be made at the 20W and the lamps work ok

case 2: the ballast burns out and uses 0 watts after a short period of using (?) watts.

case 3: the ballast can't light the lamps and uses nearly 0 watts.

case 4: the ballast tries to deliver more than 20 watts, overheats. the thermal overload cuts it out. ballast cycles this way using an intermittent (?) wattage.


I'd go with 1, but like I said, just my guess.:grin:

 

[T.C]

okay, well that was my original guess was to go with 20 watts, but I haven't studied ballasts yet, so I am just assuming that a fixture can only pull what it's ballast is rated to handle. thanks all for your assistance. you've given me several points to think on. I'll check back on this tomorrow, if anyone can think of anything to add.

 

[rattus]

that is another valid point, but the picture does not appear to represent flourescent tubes. also, we have not yet studied any sort of calculations based on relative lumen output. this is supposed to be simply the circuit calculations based on the rules of series and/or parallel circuits
let me see if I can repost the picture with the whole page

If a ballast is used, then the lamps are something other than incandescent, but that is of no importance here. I think the intent is to indicate actual power dissipation. Then there would be 120W of dissipation associated with the two lamps in question.

 

[Energy-Miser]

If a ballast is used, then the lamps are something other than incandescent, but that is of no importance here. I think the intent is to indicate actual power dissipation. Then there would be 120W of dissipation associated with the two lamps in question.

Yes I will go with the 120 w for the purposes of this work sheet. Let us know what your teacher says T.C.