Some electronic ballasts tend to behave this way, as they do not require the arc to reignite every mains half-cycle (and this mechanism fail at first)...

Quote from: Brian on November 21, 2008, 09:44:40 PM

Where I live in Queens, NY, cycling HPS lamps are an epidemic, and I HATE IT!!!!  It is SOOOO annoying.  That is why Mercury Vapor should NEVER have been banned!   

some HPS Lamps i see dont Cycle....but instead Go a Dim Orange Color and just Flicker.

Back home in Alaska cycling HPS lamps are pretty common too.  One surprising thing I noticed when I was there last, was that a bunch were in a string of fixtures that were newly installed back in 2007.  Those would only be at 1/4 of their rated life.

Some HPS lamps turn a weird blue color at the EOL instead of Cycling.

Those are the non-cycling lamps that turn blue at EOL.

Those are the non-cycling lamps that turn blue at EOL.

I have seen those this week, wondered at that.

I have seen many Metal Halide lamps usually below 100W tend to cycle at my school towards the end of the day. the arc swirls in the morning then eventually just flickers and cycles relentlessly.

I see HPS cycling commonly, and I have seen a very very few low wattage metal halide lamps cycle. Never seen a cycling MV in person, though, only intentional hot restrikes

i saw two 70w MH cycling for 2 years on local restaurant and an 250(or 500)W ML.

An interesting thing about cycling -

Its not allways the lamp that extinguishes when its voltage is too high

As the lamp voltage rises, it can get to the point where the ignitor (which is guessing whether the lamp is on or off by the vltage across it) thinks that the lamp is out. Now it attempts to start the (assumed off) lamp. When striing, the ignitor momentarily drops the voltage on the output to the lamp. Now that is what kicks the lamp out. Seen mostly with HPS

Ash, does that mean that the ignitor is at eol too ?

For cycling MV, the only time I saw it was with a lamp/ballast mismatch. It was a 175W H39 MV lamp running with a 100 W HPS ballast here in Canada.

No. They are ok and will work well if a new lamp is installed. In fact the actual fact that the lamp is cycling means that the ignitor is working properly and able to start the lamp

There are 2 common types of ignitors here :

Superimposed - measures voltage across lamp, releases a small pulse on each cycle or 1/2 cycle to start. With superimposed restriking you see dim "lightning bolt" discharge in the arc tube (in fact it is series of small discharges from the pulses)

Semiparallel - measures voltage across lamp, releases a powerfull pulse ~4 times/sec to start (self timing). With semiparallel restriking you see bright flashes of xenon/mercury color



Now the cycling lamp striked and is warming up. In a minute or somewhat longer it will reach to the point that the voltage across it is too high. Then the ignitor will decide that the lamp is off and attempt to start it

The starting attempts of the ignitor look like momentary voltage dips to the burning lamp

With the superimposed you will see the lamp brightness drop somewhat and "shake" as the ignitor begins to restrike it, with 50/60/100/120 times/sec momentary dips. This "dimming" in turn cools the lamp a bit, its voltage drops out of the region where the ignitor thinks it is off, and stops. The lamp is back to full brightnes and warming up again

So what you see is the lamp burning, dimming, beginning to shake in brightness for few seconds, going back to full brightness and so on (repeated every few sec). Then in 1 of those times where the lamp is "dimmed", it drops out on 1 of the pulses

With the semiparallel you will see (not easy to spot, but possible) "jumps" in the lamp brightness (not dips, because every dip is also followed by a flash, so they cancel out in visibility), with intervals of up to 1 in few sec. This will often go on for years when the lamp is still good, ie the ignitor allready attempts to start the lamp but the lamp is still good enough to not drop out on the dips). Finally, the lamp will not hold in 1 of them and drop out

So what you see is the lamp burning with very slight "jumps" in the light output, following a precise pattern (once in X sec or so). This can go on forever or for long time. Eventually when the timing is just right for another jump, the lamp will go out instead

Thanks, makes sense now. Either way, the situation is hard on the ignitor as it works more often than once per turn on.

It is said that cycling lamps damage ignitors (and there are even pictures of melted and burned ignitors in the gallery)

However the most common ignitor around here (semiparallel Eltam ES50) appears to be quite reliable, it can click all night for months and years on cycling or missing lamps and appears to remain working well after that.  But maybe its only this one