ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades exploding metal halide lamps

CTwireman.

the lamps are sylvania (250w MH)

the control gear is thorn, in most but an unnamed brand in others, not all the exploding lamps have thorn, but some do.

Checked capacitors on all damaged fitings and all but one is ok, (that fitting just didnt work).

Having just got home from site, (over hear its now 1930 hrs) i have found a small problem that might be the route cause of the premature lamp failures,

Its a Power Factor Correction capacitor set up, fitted over three phase supply and it seams to be leaking,

i have to go back in the morning with a couple of lads to check out this PFC capacitor set up and replace the failed lamps/fittings before opening time of the yard on monday morning.

I think that the failure of one or more of the interconnected PFC capacitors has caused a fault with the load side of the lighting.

Previously the lighting was very old lead/lag 125 watt twin fluorescents at high level, the only thing the plants electrician (i use the term loosly) did was remove the fluorecents ans put in these metal halides.

I have not looked, yet, at the cabling, switchgear etc to see if the additional loading would be detrimental to the installation but we will, the company CEO was screaming blue murder about shutdowns etc money lost, money cost, but not a word about staff safety, funny that isnt it.

will keep you posted on what i find.

John H

John,
I think you may have just found the problem.
I would say that it sounds like the PFC Capacitor is too small (capacitance and voltage-wise) to handle the surge currents of the M-H lights, this should have been uprated when the fittings were changed over.

trumpy the bulb life determed by brightness between new and old one and colour shifting yes ideed if the bulbs are clear one if you look closely to the arc tube ( of course the light will be off anyway for safty sake ) near the end of life the arc tube will deform where the path runs like sagging pattern and also if you look at the manufactures catalog book it will listed the bulb life i know 250 w mh are listed about 15,000 hours or so depend on which type but one probem most factory dont like to cycle the switch for the light they claim it take too long to come back i say balony it is better do that way because you can catch bad one before actally exploding

john i did read that part about the power factoring capatitor that is instering to know but i am not sure about it but before it get out of hand what voltage you are running i know i belive you have 250 v 50HZ if i am correct ?? if so if the phase correction capatior going bad i wondering why they should have a fuse there to protect it from somekind of surge

IMHO : the capatoir do responde diffent between flourscent and hids they are differnt due current spike is diffrent i think that what keep overloading PPC unit

merci marc

Having further checked the PFC capacitors, all three are faulty,

Marc,
the supply running the MH is 3 phase 440v
split via two panel boards side by side.

The supply characteristics are as follows.
440V ac 50hz 3 phase at 600 amp per phase.

thsi oes via the local pocos fusable link and to the meter then to main disco (1000 amp)
from the disco it goes to a Bus Bar chamber then to local discos to sub panels.

the lighting boards are fed accross the PFC capacitors via there own Discos and then to panel boards.

Having now checked the installation we have removed the PFC and i am just in the process of checking loading capacity/lamp start/run currents to be able to re specify a new PFC.
the CEO was in again and had a few words to say to me, Again, the plant electrician has not been seen for a few days and we are all wondering what the hXXl he thought he was doing.

when i get the new PFC capacitor i will let you all know the outcome, i think it will be a good one.

By for now. John H

John H,
Man, is that a supply or what!
What sort of factory is on the end of that Bad Boy?.
If I was the Plant Electrician, I would be seriously looking for another job, he obviously doesn't understand the Basics of Electricity and Power Factor.

Trumpy,

A further update on this little fiasco, the supply is quit normal for the type of building, it is a heavy plant repair shop housed in 35,000 square feet (not all plant works some offices etc,

so you can see the reason for the supply !!!

its fun to work on, as you never can tell what the hxxl is goin to happen.

Also the `electrician` submitted his resignation today and left!!!!!

the new PFC capacitors are on order, the new fittings are on order, the new lamps are on order, etc etc etc, and the CEO wants the whole of the plant repaire and offices tested and inspected and put right, he has signed a proforma works order and away we go.

not a bad job in the end, if you discount the exploding MH lamps, it should bring into the company about $24,000 for all the repairs etc that are needed to make this eelctrical nightmare safe.

I will try to get some photos of the old stuff before we take it out.

Bye for now

John H

One other good thing, my quaterly bonus is safe.!!

440V??? Phase-to-phase or phase-to-neutral? Then they must have a standard 400V service as well?

John,
Well, I'm just glad that all it turned out OK in the end!.
You must be glad of all of the exta work that this has brought on.
Just goes to show what can happen when you have a "Thinking Electrician" on-site, as opposed to a mere "Wire-puller".
However, I'm sure that this has been a learning experience for all concerned, especially the old Plant Electrician!.
Some pics of the old Capacitors would be cool!.
C-H, it must be 440V Phase-Phase, 440V to Earth, sounds a bit dangerous!

[This message has been edited by Trumpy (edited 04-14-2003).]

440V was the highest nominal phase-to-phase voltage before standardization some 30 years ago. You'll still hear it referred to sometimes, even though the actual nominal levels are 240/415V (or officially now 230/400).

If you work it out, the actual phase-to-phase voltage was 433V, but it was often quoted as 250/440V.

wow now i can get the picture what happend to the plant electrican seem he cant grasp new morden stuff around here anyway as far the light is that wired for 250 volts or wired for 415 volts ??? just wondering about that and here in north americane system for the light most common is 120 or 277 volts but have odd ball too both 208 or 240 volts but cananda do not allow use 208 or 240 per cec ( i dont know why but i will dig it up )
but canada have 347 for hid or flourescet light now that is istering my self i havent see it but i heard it plenty of it so i will check my canandnie friend to find out


merci marc