I am trying to find out the starting characteristics of Metal Halide Lamps. Does anyone know where I can find manufacturers technical information? I have found a manufacturer here in Australia, Sylvania lighting they have technical information but their links are messed up and the files cannot be opened. I am trying to find typical run, start, and inrush currents for lamps and the start up times.
Gray, I'd like to help. What bulbs/Control gear are you after the figures on?. I use quite a bit of MH gear with the local Power Board here in Ashburton. We are changing from the old Sodium lamps to MH, in a retro-fit situation. There are bulbs that can do that.
#142788 - 03/01/0505:20 AMRe: Metal Halide lamp technical information
OK Gray, How many sets of control gear are on each contactor?. I'm not that conversant with the AC ratings, but AC 3 sounds a little low for an Inductive load like that. I'm told that the AC 22 or 33 is the one to use with Inductive loads. And another thing with respect to the resistive rating of Contactors, at laest halve the current rating for Inductive loads, where a contactor could carry 10A resistive, it only as a rule will carry 4A Inductive. Ask the guy to get a heavier contactor, say 50A or run 2 in parallel.
#142789 - 03/01/0506:19 AMRe: Metal Halide lamp technical information
Dapo I think the AC3 rating is for motor loads. Contactor manufacturers usually publish their ratings in their catalogues with helpful tables on light fittings per contact and switching frequencies etc. You should look at the number of operations of the faulty contactors before buying replacements.
#142790 - 03/01/0504:30 PMRe: Metal Halide lamp technical information
Yes, AC3 ratings are for squirrel cage induction motors, AC1 are resistive loads. Power factor correction doesn't necessarily reduce inrush current.
These lamps when struck from cold use mercury vapour to warm the halide, when warm the potential on the electrodes pushes away the halide plasma so they need a very high strike voltage to get them started over again. But even that would be only wery short current spikes.
Squirrel cage motors present a heavy inductive load only during startup for a few seconds at most, whereas these lamps could be highly inductive for literally minutes as they warm up. I'm surprised they don't have guidance on what contactors to use in the installation paperwork?
Do they have a simple ballast or more sophisticated control electronics?
#142791 - 03/01/0507:16 PMRe: Metal Halide lamp technical information
It is most likely the power factor correction that is giving your contactors such a hard time. Depending on whereabouts in the mains cycle the contactor closes, PFCs can and do generate savage inrush transients that chew contactor contacts. Contactor manufacturers are aware of this, and do publish tables giving the derating factors for different combinations of contactor and lights. I advise you to seek the wisdom of your contactor manufacturer.
Mark aka Paulus
#142792 - 03/02/0503:41 AMRe: Metal Halide lamp technical information
I think they were 250W metal halides with standard ballasts (non electronic) and fitted with PF correction capacitors.
The AC3 rating is indeed a motor current rating. Someone said there is a rating for lighting contactors and it is designated as AC21 though I have not seen this rating personally.
I am not sure how many lamps are on each circuit only that the total load per circuit is between 13 and 17 Amps You are right Mike if I were the contractor I would have looked at a larger size contactor before now. I still find it disturbing that the neutrals on the terminal strips, are getting hot enough to melt the plastic of the strips. I was told that the rating of these strips was matched to the contactor ratings.
Kiwi if you have any links to manufacturers which have data on numbers of light fittings for contactor sizes it would be appreciated.
There shouldn't have been too many operations on the contactors as this all part of new work at an Abattoir boning room which was commissioned only three months ago December last year. I would think there would be only two operations per day, one at the start of the shift the other at the end of the day. This would be far less than the thousands of operations a correctly installed contactor should be capable of.
gideonr, looking at the manufacturers tables, most metal halides seem to draw about 120% of their full load currents between 1 and four minutes.
Paulusgnome, I have read in one cataloger that the contactor must be able to withstand the inrush current for power factor corrected fittings and they that the inrush for these fittings is almost the same as incandescent lighting.
Thanks your help guys.
#142793 - 03/02/0501:45 PMRe: Metal Halide lamp technical information