Gallery of Lights
Lanterns/Fixtures => Modern => Topic started by: A_lights on March 23, 2013, 09:07:00 PM
-
Never tried this but i wonder if it would act as a NPF ballast? or would the lamp just remain dim as if it wasn't getting enough power? i know the NPF balalsts have an optional capacitor though
-
npf ballasts can have caps? i thought if you added a cap it became a HPF ballast. do some HID ballasts not run lamps at max. potential power like fluorescent ballasts or do all HID ballasts run lamps at the same number of lumens as the lamp says? with fluorescents it's confusing since the lumen rating on the lamp sleeve really means nothing without knowing the ballast factor. >:(
-
Every HID ballast I've seen in the specs shows 1.0 ballast factor meaning it gets powered fully at the lamps rated wattage
-
@A_lights: Do not mix up the Ballast factor (that youaredescribing) and Power factor.
Ballast factor say, what would be the lamp output on a ballast under question, relative to a reference ballast. SoBF=1.0 mean lamp run atit's rated power.
But the "Power factor" mean, how the ballast utilize the upstream wiring. It is defined as PF=RealPower/(Vrms*Arms).
It become unity with only exactly resistive load (soe.g. a heater and/or incandescent lamp).
For other real load (ballast, computer, motor,...), where the current waveform isoff phase and/or a different shape than the voltage, the PF is below one. E.g. the mains current is 4A at 120V, the real power input is 300W, so the power factor of such device would be 300W/(4A*120V)=0.625.
For the "CWA without cap" the first thing it mean, it won't be a CWA anymore, but something like HX autotransformer.
The CWA isbased on a resonance effect together with core (magnetic shunt) satruration to keep the lamp current constant over wide range of external conditions, mainly the input mains (so it's main task isto compensate out the mains variation).
When you remove the cap, the "regulation" effect will be in fact reversed (so higher mains voltage would cause even higher lamp current) and it is a question, how the result will behave.
I would guess the ballast is designed so, under such condition it would run at lowwer than ratedcurrent, it won't saturate, as capacitor short circuit is a failure mode most likely anticipated bythe ballast design (assume quality ballast).
But with some ElCheapo ballast this assumption does not have to be the case and so such configuration may overload both the lamp, as well as the ballast coil.
-
It would be interesting to try. I have tried it before on a universal pulse start Metal halide ballast which caused the primary auto transformer winding to overheat and burn up. Live voltage was 120. The lamp started normal but as it was warming up the primary winding started to get very hot and eventually started to smoke few minutes latter. Obviously the windings were seeing more current for what ever reason, my guess the reduced power factor took its toll.
If you try it on an older ballast let us know :)
-
@Keyless: It was not as much the reduced power factor, but most likely the too low impedance in series with the lamp.
Apparently someone's observation than when the capacitor get shorted it cause lower than rated lamp current (made with MV ballast) is really apparently not true for all ballasts.
I would not risk burning out the CWA, when they are not made anymore...
-
@Medved
Thanks! I was wondering what it was that caused it. Normally I wouldn't wreck a good ballast but I had a case of these and was feeling adventures in the name of science, Ive always wondered what a shorted cap would do.
-
Then with such experiments just monitor the temperature and stop it in time, before it get really hurt... For the bulky copper&coil things the only enemy is the heat and it always take time to build it up, so it is not too difficult to spot the unusual heating in time...