Metal Halide M-81 Lamps

[jmd445]

I was working with a new member to my crew and were were replacing bulbs and ballasts for roadway lighting. The ballasts were Advance ballast kits 71A5490-500D and Phillips CDM150/TD/830 Lamps



He was getting disgusted since several lamps wouldn't ignite after replacement and was ready to throw in the towel. I went to help and just reversed the polarity (flipped it 180 degrees in the socket) and it ignited. Are these lamps polarity sensitive, obvioulsy they are, but I can't find and reading material on the net regarding this.

Assistance would be appreciated.

Jim

 

[Dennis Alwon]

I never used one but I can't imagine they are polarity sensitive. My guess is the bulb wasn't in the socket well enough on the first try.

 

[LarryFine]

My guess is the bulb wasn't in the socket well enough on the first try.

I agree. Just like tubular halogen lamps, it's easy to not get the end contacts centered in the porcelain ends of the tube.

 

[jmd445]

I first thought that it might not be mounted correctly in the pins, so I remove and reinserted the lamp, no good. Then I turned it upside down in the fixture, no good. Then I reversed it's polarity and it lit!!!!

I set up a bench test with the bulb, cap, ignitor combination and produced the same results.

Jim

 

[mxslick]

A lot of arc lamps are polarity sensitive, as the arc electrodes are usually shaped to help in the ignition of the arc.

In the case of the xenon short arc lamps used in cinema projectors and those sky-scan searchlights, the bulbs MUST be connected with correct polarity!! Any reverse polarity will instantly destroy the lamp for good, sometimes by explosive failure!

A Google search for "OSRAM" will lead you to thier website, they have an excellent technical paper availble for download on the theory and operation of Xenon short arc lamps.