On 04/11/12 13:51, Andrew Gabriel wrote: .
I love it when someone start a paragraph with an assertion, and then totally demolishs it with the arguments he brings to support it.
The way this is resolved is to reduce
And then completes the buggers muddle with a totally false statement.
electronic ballasts I'd probably put the cap between ballast and tube.
I think you must mean with LC ballasts as used in lead/lag lights. 50Hz L ballasts have no crest factor problem.
NT
electronic ballasts I'd probably put the cap between ballast and tube.
It's not a problem above 5kHz, because tube doesn't stop conducting between half-cycles. It's a big problem at 50Hz where tube stops conducting and is restruck every half-cycle, because at the restrike, there's nothing much limiting the in-rush current to change the voltage in the capacitor, apart from the arc with its negative resistance, and the mains supply impedance. In effect, you end up with the capacitor discharging the sum of the drop-out voltage from the last half-cycle and the restrike voltage from the current half cycle (which is typically somewhat over 100V) straight across the tube, limited by the impedance of the mains supply. This current pulse
100 times a second rapidly wears the electrode coating off.reduced tube life
from them. The choke's properties avoid excessive crest current
That's what the L is for in a leading circuit.
ballasts have no crest factor problem.
I meant purely capacitive ballasts, as you mentioned in your previous post. The LC (mainly C) used by Thorn knocked the crest factor down, specifically to get reasonable tube life.
electronic ballasts I'd probably put the cap between ballast and tube.
and the choke's R&L
reduced tube life
life from them. The choke's properties avoid excessive crest current
yup
ballasts have no crest factor problem.
I didn't mention C only ballasts at all :)
NT
Which bit, the higher efficiency or the different colour temperature?
I have always observed a much "whiter" light from 12V LR16 lamps when compared with say GU10s though.
(even a 20W LR16 is whiter than a 50W GU10)
or 4 times... Some of my LR16s claim 4000 hours. Most "normal" filament lamps seem to claim 1000.
Some "extra long life" GLS lamps will do 3000 hours, with a little less light output.
Probably to create the impression that you have modern discharge style headlamps!
(there is some benefit to a slight blue colour however, in that it gives a stronger contrast on the white road markings in some conditions)
Yup that is fair enough. But where does the colour shift come from on LV halogens wrt mains?
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