Author Topic: Make a normal ballast high power factor?  (Read 245 times)
Lightingguy1994
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Make a normal ballast high power factor? « on: August 09, 2019, 06:30:38 PM » Author: Lightingguy1994
I have a capacitor that i removed from a small fan. Its rating is 4uf at 250v ac with two wires

Was wondering if it could be used with a normal power factor ballast to make its pf higher. I have ballasts ranging from 2xF6T5 to F40T12 1 and 2 lamp that are NPF. If this can be added to it externally i woukf need to know how to wire it and to what leads.

Just curious and itsmore of a experiment not worried if it cannot be done.
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Re: Make a normal ballast high power factor? « Reply #1 on: August 09, 2019, 09:18:48 PM » Author: High Intensity
I think all you have to do is connect the capacitor across the input leads on the ballast. But i don't think this will affect the way the ballast works in any way (other than changing the PF).
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Medved
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Re: Make a normal ballast high power factor? « Reply #2 on: August 10, 2019, 01:03:30 AM » Author: Medved
Rising power factor could be indeed done by such capacitor (assume it is a lag ballast), but only if we are talking about "magnetic" ballast.
With electronic ballasts the low power factor does not come from any phase shift (there is none at all), but from higher harmonics in the current waveform (the spikey nature of the current drawn by a capacitively loaded diode rectifier). This type of low power factor you can not correctby any simple means, it is practically feasible only by the electronic using a power factor corrected rectifier.

But the main question remains: Why?

I have some "guts feeling" what you are actually looking for not high power factor, but for full ballast factor.
Why: Power factor says only howmuch current the thing will draw from the mains at a given power. Usually important only with large installations, where it makes difference on circuit sizing (the wire gauge,...) and where the reactive power is billed by the utilities. And there you wont be allowed to do any such modifications, because of lacking UL certification.
 With one or two fixtures at home you will definitely be way bellow the ratings of the thinnest code compliant wires or common breaker ratings, plus homes are billed only for real power, so no benefit there either.
What dictates how much the lamp will light is the ballast factor.
The source of confusion is, the ballast products intended for commercial use useto have both power factor, as well as ballast factor unity. The reason is, this leads to the lowest large scale installation costs.
Home ballasts tend to be of low power factor, because the home use (small space) asks for rather lower intensity light, the F40 were used just because they were the most common so cheapest type and still did not have any significant efficacy penalty even on lower power use (compare to an eventual dedicated lower power lamp design), so the solution was to use the 40Watters and power themjust by about 25W.
The low power factor was chosen, because simpler and so cheaper way of designing a ballast.
But technically these parameters are completely independent on each other.
So the high ballast factor products used to be high power factor and vice versa, often with shortened description mentioning only the power factor as a difference, leading to a misconception of the power factor having anything commonwith lamp output other just the correlation of which products were marketed.

And rising ballast factor is way other story - that is practically impossible without completely rewinding the whole ballast.
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Lightingguy1994
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Re: Make a normal ballast high power factor? « Reply #3 on: August 10, 2019, 11:15:06 AM » Author: Lightingguy1994
I actually did forget that ballast factor and power factor are two separate things. There isn't any pressing need for me to go through the trouble outside of pure curiosity. One thing I have noticed over my years of lighting is HPF is always better. Every ballast I have runs well, even if its lower power. They still start reliably until the very end of the lamps life and they always have proper electrode heating. Two lamp NPF ballasts the electrode heating is too high and overdrives the filaments and they glow bright, my F6T5 magnetic ballast had this issue but I soldered in a diode onto one yellow lead and that fixed it. The other issues Ive seen with NPF is they will not run the lamp to true EOL, they rectify before the electrode even breaks and they experience starting trouble.

I'm not interested in ballast factor, Im trying to see if making one HPF will bring better performance but in the end it doesn't matter as I can just get real HPF ballasts.

As for why I want HPF, the performance issues I noted above with NPF ballasts.. but also NPF uses more current. As you know , residential electrical panels are limited in the Amp rating. usually around 200 or so ( i think ) depending on house size. Keeping my lights at high power factor will reduce the over current demands on the service panel. NPF will no doubt bring it to the limit. Lastly, I like commercial grade lighting so they must be HPF for that reason too. A healthy quality ballast will allow long service life to the lamp
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Re: Make a normal ballast high power factor? « Reply #4 on: August 10, 2019, 11:51:05 AM » Author: Lightingguy1994
My 2xF6T5 fixture with a magnetic trigger start NPF ballast test with the cap.

Cap: 4uf 250v 5%+/-

No cap:
PF = 0.41
A = 0.44
W = 22

With Cap:
PF = 0.65
A = 0.28
W = 22

Pretty cool. Likely will keep fixture NPF however
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Medved
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Re: Make a normal ballast high power factor? « Reply #5 on: August 10, 2019, 01:57:51 PM » Author: Medved
Well, the performance differences are more linked to the ballasts being commercial vs residential grade, the power factor is usually another thing linked to that market difference. But adding a correction capacitor (the maximum you may really do) may make the thing HPF, but all the lamp related performance stays the same as it was before.
The reason the low ballast factor ballasts use higher heater voltage is, they have to compensate for the lower arc current, so the filaments remain at the same temperature as they are designed for and where they operate at full power arc current. Without that the lamp will exhibit significantly shorter life.

And for the current limits at home: How many fixtures you have to have to use even a small part of it...
In commercial installations are used the same 15A breakers per lighting circuit, but tens of fixtures on it. Then the current becomes really important - as it is quite significant difference, if for e.g. 200 2x40W fixtures they have to use 15 vs 30 circuits...
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Lightingguy1994
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Re: Make a normal ballast high power factor? « Reply #6 on: August 10, 2019, 02:10:16 PM » Author: Lightingguy1994
On the 2xF6T5 only the filaments on the yellow wires were grossly overdriven, the red and blue wire side was perfect. The diode I placed on the yellow lead made the voltage much closer to the others and now its just right. Lamps are new and despite many start tests still have not a speck on them.

Commercial installs here can be 120v at 15A yes, but its more common for them to have 20A and even more common to have 277v or 347v. My old classroom in elementary school had rows of 4xF40 louvers (each only lamped with 2 lamps). One day when the teacher was using a hot plate to cook something during an activity, it caused the breaker to trip which made only a few fixtures in the room and a few in the room next door go out also. This means that there are more than one 15A 120v circuits.

In a house I wont have the luxury of having the lighting on its own 15A feed, it shares it with some outlets in the room also. So for example if Im using high current sucking NPF fixtures each taking 1.3A a piece when factoring in the power factor, I will have a lower capacity left on the power outlets on the same circuits leading to popping breakers often. If i use HPF , the current dram is less than an amp will will provide more amps left at the outlets. You seen by the test I did, the fixture drew less amps when using a capacitor vs without.

Now keep in mind Ive expressed this to the best of my knowledge and I could have errors in my thinking. If I am wrong it is no problem I would like to learn.
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