Control/Dimming HX601 and HX401 lamps failing very early

[SteveRR]

I'm helping a friend with this, so I don't know a lot about lighting systems, forgive me for that, but I am an electrical engineer so I have some relevant background.

These lamps are on a Leprecon Litescape LWD –2400 dimmer. These lamps are rated 1,500 hours, but they are getting a fraction of that, probably less than 50 hours on average. The dimmer manufacturer isn't much help. When the lamps burn out they do not get carbon inside the lamp, the filament just melts off at both ends where it attaches to the posts, and breaks into two or three pieces. What might cause such early failures? Using a voltmeter, the voltage into and out of the dimmer seems pretty steady. Looking at it with an oscilloscope, the output is pretty severely distorted under high load (the sine wave stays flat at 0v each time it crosses from positive to negative). I'm not sure if that would affect the lamps or not. They have probably 50 or 60 lamps that are having this problem.

I don't believe the lamps are subject to severe vibration. Also, the fixtures are mounted vertically (aimed straight down), my friend tells me they are rated for vertical operation. He is now using Ushio lamps, and I believe has tried other manufacturers with similar results.

Here is information on the dimmer:
Leprecon Lighting for Professionals

Any help with this would be greatly appreciated!

 

[DimmerDotCom]

These are 115VAC lamps I believe. What is your voltage on them? 120? 130? Do you see metalize particles on the glass when they blow?

edit: Metallization occurs when the migration of tungsten away from the filament occurs at an explosive rate. Temperatures above 200 degrees F also increase tungsten migration. Filament failure also occurs most often when no current is flowing and the filament is at its most brittle (the advantage of a dimmer system with a 5 second fade up time for architectural lights). Running lamps above their rated voltage also decreases their life.

The following formula can be used to re-rate lamps:

re-rated life = rated life x ( rated voltage / applied voltage)^12

Therefore, the 115VAC 1500-hour lamps running at 120VAC would have a life of:

1500 x (115 / 120)^12 = 900 hours

“The average life ratings published by lamp manufacturers (and included in the tables that follow) are based on tests performed under laboratory conditions: stable ambient temperature, no shock or vibration, filaments operated on AC voltage-regulated to plus or minus one percent. Average life is the elapsed time after which 50 percent of the lamps under test have failed. Failure includes a current increase to 10 percent above the initial current value and/or a brightness decrease to 20 percent less than initial brightness"

 

[mstaylor]

Can you see any reason other that voltage that the instruments would be conducting excessive heat.

 

[TimMiller]

i had something similiar happening on some dj lights a while back. Turns out the lamp sockets were bad. Also the chopping you saw on the scope is normal. There are only a few dimmers that do not do that, and those are true sinewave dimmers. I would definately compare the lamp rated voltage to the voltage that is being fed to them.

 

[derekleffew]

The fragility of the filament of the FLK/HX601 is well-documented. In what fixture are these being used? What is the actual voltage at the fixture? Does the dimmer allow for a maximum output limit? You might consider the GLA/HX-605 lamp as a direct replacement, but with an improved filament structure.

 

[NevilleLighting]

Also, check the lamp bases and the pins on the lamp for carbonization. If the lamp is not seated well they will produce an arc in the base which will lead to higher operating temps which can drastically reduce lifespan.

 

[TimmyP1955]

The following formula can be used to re-rate lamps:

re-rated life = rated life x ( rated voltage / applied voltage)^12

Therefore, the 115VAC 1500-hour lamps running at 120VAC would have a life of:

1500 x (115 / 120)^12 = 900 hours


What is ^ (or ^12) in this equation?

 

[derekleffew]

...What is ^ (or ^12) in this equation?

"Raise to a power of..." (exponent). It's MS Excel speak.

 

[Soxred93]

It's MS Excel speak.

Not exactly, ^ is used in a lot of computer programming applications to signify an exponent.

 

[FatherMurphy]

What fixture do you have these in? Is it possible that the fixture isn't rated for the wattage, or lacks enough cooling airflow in the position it's hung?

How are they programmed? Bump on to full from cold and dark, or fade up?

The HX-601 and HX-604 lamps are also known as GLC lamps, and are 3200 Kelvin lamps and have somewhat short lives. The HX-605 is also known as GLA, and is a 3050 Kelvin lamp, which is probably the long-life version you think you're buying. The two types are virtually identical in appearance, so you'll probably have to pull one and read the base to be sure.

If you're using the Leprecon LWD-2400, and have fixtures pointed straight down, I'm guessing they're being used for house lights in possibly a church setting. The LWD has time-of-day triggers available for cuing, you might consider adding a pre-heat cue of 15 or 20% to automatically execute and warm the lamps a half hour or so before the space is normally used. This would cut down on the thermal shocking, and wouldn't add significantly to the electric bill.