Wikipedia:Reference desk/Archives/Miscellaneous/2012 January 12

= January 12 =

Calculation of Flourecent power usage.
Good morning.

I did a liitle experiment with a flouresent light and just want to share my findings in oder for you to add it to you encyclopedia.

I wanted to determine the amount of watage my light draws and the only 2 things i could measure were Voltage and Current. I then connected my multimeter to the light and measured 240V and 0.196A if i calcultae the power it is 240*0.196=47W. which is very close to the 40W tube installed. I then wanted to see if the system will draw any power without the tube inserted, because if you disconect a normal globe from the socket there is no current flowing, and this is where the suprise came in.

My multimeter showed current of 0.285A without any tube connected. this means that without the tube the system is drawing 68W which is 21W more. I realised this is the initial start up current with the tube connected.

In other words the balast and starter uses power continuesly without the bulbs connected. This then shows that it does not help to remove a tube from the fittings thinking that you will save power, the balast will keep on drawing power trying to start a tube that does not exist. — Preceding unsigned comment added by 41.208.40.36 (talk) 12:26, 12 January 2012 (UTC)


 * Your measurements do not take any account of the phase discrepancy between your measured voltage and amperage. See AC power for details, especially the mention of "wattless power".    D b f i r s   12:38, 12 January 2012 (UTC)


 * Please note also that we are not in the business of publishing Original Research such as this. That is the domain of other organisations. We aim to record established information. The policy article No original research may be worth reading. --jjron (talk) 15:14, 12 January 2012 (UTC)
 * Do not scold the questioner; just provide referenced answers,and steer him to relevant articles. His calculations of volts times amps for AC result in "volt-amps" which are a combination of real power and the "reactive power" 90 degrees out of phase. It is surprising (to me) that the fixture would draw more current with the bulb disconnected. "Guide to energy management" by Capehart et al(2003), page 180 says that "rapid-start" ballasts continue to consume current when the lamps are removed, but "instant start" ballasts stop consuming current when the lamps are removed. Some ballasts are plain old magnetic coils, but modern ones are more efficient electronic ballasts. "Handbook of energy efficiency and renewable energy" by Kreith et al (2007) p12-38 says that rapid start ballasts apply continuous low voltage to the filaments to heat the cathode, as well as a spike of high voltage to start the arc so the lamp conducts current through the gas. Instant start lamps do not preheat the cathode. Thus you might have any of these kinds of ballasts in your lamp. Edison (talk) 04:28, 13 January 2012 (UTC)
 * This is the concept of power factor: you need to size your wires for the volt-amp rating of the load, while the generator needs to be sized for the (usually smaller) wattage rating. Fluorescent lights tend to have a very poor power factor. --Carnildo (talk) 02:01, 13 January 2012 (UTC)
 * Generators certainly produce vars as well as watts. The ability to produce watts is decreased by the production of vars, in a nonlinear way. A utility scale generator can be spun up to synchronous speed with a pony engine and used as a synchronous condenser, producing only vars for reactive support of a power system, (keeping the voltage up) even if the boiler has been decommissioned. Edison (talk) 04:28, 13 January 2012 (UTC)
 * Does your "synchronous condenser" use its reserve of energy (half moment of inertia times angular velocity squared) to "even out" the power variations across one cycle?   D b f i r s   01:00, 14 January 2012 (UTC)
 * Once an auxiliary motor has it rotating at synchronous speed, it acts like a generator of vars, powered by watts. It provides reactive support in a better way that a capacitor bank, which produces less voltage support as the system voltage drops, setting a utility up for voltage collapse. It could also be used to lower system voltage, but a far easier way to do that would be through action of the voltage regulators on the generators. Edison (talk) 15:09, 17 January 2012 (UTC)

Cannot locate a topic and need help
Hi Wikipedia friends, I need to locate some background material about racial segregation in the United States. I have tried to find it myself on your site without success. Any help in directing me to some pages will be greatly appreciated.Lightingcandles2 (talk) 12:56, 12 January 2012 (UTC)
 * Racial segregation in the United States, not too hard that one. --Viennese Waltz 13:00, 12 January 2012 (UTC)