230V light bulb power drain at 115V??

[Behemot]

I got two lamps 230V/100 W together for loading UPSes after battery swap. The thing is, I got arround 7 UPSes for american power grid (115V), but only one 230/115 transformer. So I will renew only one of them. (I can use them for powering Cisco Catalysts, they eat 115 V as well)

But the problem is, I do not know what to load it with. I do not want to use any ordinary PSU because of power factor, light bulb is ideal for me. They will work at 115 V, sure, but what would be their power drain from at 115 V? I need the most exact number if possible to determine battery capacity (whether it +- correspond with new bats capacity).

[budm]

Re: 230V light bulb power drain at 115V??

What is the make and model number of the US UPS?

[Behemot]

Re: 230V light bulb power drain at 115V??

It is some Manhattan. And yes, I had a look, it is only able to work from 110-120 V/50-60 Hz grid, no greater range. Thats written directly on it.

[budm]

Re: 230V light bulb power drain at 115V??

Usually the model number will indicate the VA rating, for example APC-850 is 850VA (550W).

[Behemot]

Re: 230V light bulb power drain at 115V??

Its 1200 VA. I don't really see how is this helpfull? I need to know what power a 230V lightbulb (60+40 W) will drain on 115 V (UPS's output). Than I will let it run on batteries and from the runtime calculate battery capacity. Than I will compare it with nominal capacity and see whether it corresponds somehow, or I will have to do some calibration.

I do that with 230V UPSes just fine…here is the problem that I obviously do not have 115V bulbs, you see

[budm]

Re: 230V light bulb power drain at 115V??

1200VA UPS will have 790Watts Rating this will tell you how much your batteries will have to at least supply the power to the load, so the the run time will depend on your batteries AH rating. You have True RMS DMM with AC amp function right? Just put the meter in series with your lamps to take current readings and another True RMS meter to read the voltage then calculate the Wattage. Now do you see why the VA that I ask does matter? You can still use your 230V lamps as the load, all you care is how much power your lamps are drawing from the UPS. I use heat element for testing ou UPS products.
http://www.engineersedge.com/battery...ry_ratings.htm
http://gbindustrialbattery.com/Batte...H_Ratings.html
http://www.dcbattery.com/faq.html

[Behemot]

Re: 230V light bulb power drain at 115V??

Been thinking about that, yeah. Because on ohmic load you can just multimply current and voltage to get power drain even on AC, right, as there is no power factor

I know what batteries I will use very well - highest capacity what could be squeezed inside every UPS In this particular case they are the same as original - 2x17 Ah 12 V. Thats 408 Wh nominal.

[budm]

Re: 230V light bulb power drain at 115V??

"Been thinking about that, yeah. Because on ohmic load you can just multimply current and voltage to get power drain even on AC, right, as there is no power factor" That is correct, that is why the resistive load is used since PFC will be = 1.

[Behemot]

Re: 230V light bulb power drain at 115V??

Yep, that is why I have chosen that, cause of knowledge it will drain current corresponding to those 100 W and nothing more.

Just have to be carrefoul, U know, messing with 115V cables arround is not too safe, not mentioning my multimeter can handle currents over 200 mA only for some short time…

[budm]

Re: 230V light bulb power drain at 115V??

Your meter cannot do 10A AC? I deal with with voltage at 6000V 3000A for surge testing everyday.

[Behemot]

Re: 230V light bulb power drain at 115V??

Yep, 10 A for a few seconds only…but I am not sure whether it even is for AC, have to have a look.

[momaka]

Re: 230V light bulb power drain at 115V??

Yep, 10 A for a few seconds only…but I am not sure whether it even is for AC, have to have a look.

If it's a cheap 830 variant, it's only for DC. I *think* you may be able to use a diode to rectify it in order to measure it.

[Behemot]

Re: 230V light bulb power drain at 115V??

Yep, its DC only. Wouldn't rectifying increase voltage?

[joshnz]

Re: 230V light bulb power drain at 115V??

The 2 lamps in parallel will use around 100 Watts at 115 volts.

[momaka]

Re: 230V light bulb power drain at 115V??

Yep, its DC only. Wouldn't rectifying increase voltage?

No.
AC line voltage is measured as RMS, but the actual peak of the AC wave (the amplitude) is near sqrt(2)*line voltage... so ~311 V peak for 220 VAC RMS and 325 V peak for 230 VAC RMS.

[Behemot]

Re: 230V light bulb power drain at 115V??

Yes, but RMS multiplied by current equals to power for resistive load. Not sure whether the power will stay the same after rectyfing for higher voltage (means also higher current than, even though not linearly due to the temperature).

[budm]

Re: 230V light bulb power drain at 115V??

"The RMS value of an alternating current is also known as its heating value, as it is a voltage which is equivalent to the direct current value that would be required to get the same heating effect. For example, if we applied 120 V AC RMS to a resistive heating element it would heat up by exactly the same amount as if we had applied 120V DC."
So for the generator to produce the same power as 120VDC, the generator will have to put out 338.4V Peak-to-Peak or 120VRMS.
So "The 2 lamps in parallel will use around 100 Watts at 115 volts." is correct. I used resistors/lamps for loading every day when I work on AC voltage regulators for both US and Euro products. Our biggest AC regulator is rated at 230VAC 30A, weights about 100lbs.

http://en.wikipedia.org/wiki/True_RMS_converter

[Behemot]

Re: 230V light bulb power drain at 115V??

Well, I am just not sure whether it works on light bulbs 100 %. Their power drain is heavily dependent on temperature…

[budm]

Re: 230V light bulb power drain at 115V??

That is why you let the resistors or lamp reach its temperature in the control room that maintain ambient temperature, beside you will used calibrated AC amp meter and AC RMS volt meter both with graph outputs to monitor the load to make the calculation.

[Behemot]

Re: 230V light bulb power drain at 115V??

I mean temperature of the wire inside bulb. It increases its resistance with great margin cause of temperature over 1000 °C.