Author Topic: HID lamp arc voltage  (Read 853 times)
mdcastle
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HID lamp arc voltage « on: June 06, 2016, 10:00:41 AM » Author: mdcastle
Do all US sodium lamps use 55 volts?
What is the arc voltage of mercury vapor lamps?
Would it be possible to design a mercury lamp to use a choke type ballast at 120 volts?
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Medved
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Re: HID lamp arc voltage « Reply #1 on: June 06, 2016, 04:47:45 PM » Author: Medved
HPS are two kinds:
The lower power ones (150W S55 and below) are designed to work with just series reactor ballast, so these are limited to the 55V arc.
The higher wattages (S56 and higher wattages) use more efficient arc arrangements, where the arc voltage is higher. The arc voltage is different for each wattage (unlike 230V markets, where all are in the 70..90V range).
The reason is, the optimal arctube voltage for the lower wattages is so close to the 55V limit, it makes better sense to sacrifice some arctube efficacy by reducing the voltage to the 55V and use just a simple series choke with way lower losses (assume same weight and ballast cost limits).
For the higher wattage the efficacy loss would be too much, so then the transformner ballast are used anyway, so then the arctube voltage was set to yiled really the best efficacy for the power rating. So except S56, any other HPS are different and not compatible with European spec HPS of the same power.
So US lamps of lower power are 55V, the rest varies according to the wattage from 70V up to more than 200V (I do not remember the standard there).
The European lamps are all in the 70 till 90V range.


The MV's inherited specifications from the British Osira lamps, so arc voltage around 100V (till 130V for the higher wattages). As Gt. Britain had all the time 240V, the spec's are tailored for series reactor on that 240V mains, that means all MV's need some step up transformer style ballast in all 120V areas.
So all MV's are in the range of 100 till 130V arc voltage (usually higher wattages allow less margin towards OCV, as the fatter arcs tend to be are more stable).

The metal halide specifications came from two directions:
One uses MV's specification as the base, because the MH's were more an MV evolution. Only later was found, the starting reliability of the probe start lamps is way better if the ballast OCV is higher, so the MH ballasts were redesigned to have higher OCV (but retain the rated arc current at the same operating arc voltage). The same approach was used in Europe, but since European ballasts do not offer any possibility to easily boost the OCV (it is just the mains voltage), the've added ignitors/pulsers to generate higher voltage pulses to start the lamps.
So the probe start MH's and some mainly higher wattage pulse start types have the arc voltage in the 100 till 130V range, same as MV's.

Now when the HPS technology arrived, for Europe that means redesigning the ballasts for lower arc voltages so higher currents, because the HPS need more OCV margin (because the arc voltage is rising over the course of the lamp life). And because HPS systems already featured ignitors, someone got an idea to design the MH lamps so, they are compatible with the HPS gear. That means quite some advantage for the European area, as the MV systems did not have any ignitors, but the existing HPS already did, so need no change except just replacing the lamp, when upgrading to MH.
So all newer MH development (mainly the lower power types, which came later) are designed along European HPS specifications.
And then these lamps, with these spec's arrived to the US as the "pulse start" MH lamps, so they share the spec's with their European counterparts, so arc voltages between 70 and 90V...
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