I came up with an idea and drew it all out. It is a metal halide bulb, but with one starting probes on each end of the quartz discharge tube, each probe being connected to the opposite main electrode through a resistor and with a bimetallic strip as usual (but twice).

If my predictions are correct, this should lower the necessary OCV of the lamp enough to allow it to strike on an MV ballast. More details are in my gallery post that I will link here once it gets admin approved.

Edit: Here is the link:
https://www.lighting-gallery.net/gallery/displayimage.php?album=lastup&cat=0&pos=3&pid=256836

What do you think?
 

Iwasaki/EYE made such probe-start MH lamp. Also European Philips HPI-BUS 400W/P is a probe-start MH lamp with one starting probe and a neon-argon penning gas which operates directly from MV ballasts without ignitors.

I came up with an idea and drew it all out. It is a metal halide bulb, but with one starting probes on each end of the quartz discharge tube, each probe being connected to the opposite main electrode through a resistor and with a bimetallic strip as usual (but twice).

If my predictions are correct, this should lower the necessary OCV of the lamp enough to allow it to strike on an MV ballast. More details are in my gallery post that I will link here once it gets admin approved.



What do you think?
 

I am aware that GE’s “I-Line” lamps achieve something similar, but the newer 400W “I-Line Plus” lamps have some form of voltage doubler circuit that uses a CWA ballast’s series capacitor to double the voltage to help with starting.

See here:

https://www.lighting-gallery.net/gallery/displayimage.php?album=search&cat=0&pos=12&pid=189390

As I understand it also, the 500 watt MBTF lamps made by Thorn had a starting problem that was actually identified by Philips!, (or it could have been the other way round?), don’t quite remember now?, anywho,
The Thorn lamp only had one starting probe that could get shorted out by a blob of mercury dropping between it and the main electrode, stopping the lamp from starting, and from this Philips add two starting electrodes to stop this happening?

I don't think it would lower the necessary OCV, it would "only" make the starting more reliable (if the auxiliary probe got shorted to the main one by e.g. a mercury droplet, the other side would still ignite the lamp), but this is more related to pure mercury, as there the mercury dose really forms conductive droplets. In MH the nongaseous fill uses to reside in the form of solid salts, which when cold and solid state are not conductive, so do not prevent the starting probe from doing its job.

The OCV limitation of MH comes mainly from the ability of the cold electrode discharge to carry sufficient current to sustain the arc and to warm up the electrodes, which won't change with two starting probe design. And to allow the gap from the auxiliary probe to spark over, where the existence of two probes won't help either.


On the contrary, having the starting probes on both ends would create reliability problems, increase the risk of one side to be flooded by the condensing salts when cooling down. Then after restrike, as the thing is warming up, the just melting salts tend to be extremely aggressive towards anything metal when there is an electrical potential difference involved, so attack the leads when the salts are just starting to melt while the bimetal is not yet ON (could happen some seconds after ignition). When starting probe is just on one end, you can more easily design the lamp with fewer position restrictions yet still completely avoiding this problem (position ratings like e.g. "all burning positions except BaseDown" and having the starting probe at the base end, so the condensing salts will never flow towards the end with the starting probe...).

Even if the starting resistors are shorted to the mains electrodes via a bi-metallic strip when the lamp is hot, I would follow Medved things.