Osram 310/360w Vialox NAV-E Mercury Retrofit

1 x 310/360w Osram elliptical coated high-pressure sodium lamp designed to replace 1 x 400w high-pressure mercury vapour lamp on the existing control gear which gives a significant increase in luminous flux and a small energy saving.
Unlike other retrofit lamps which feature a penning gas mixture, this lamp relies on an internal thermal "snap starter" for ignition which fires off with a nice ping. It takes quite a while to reset after the lamp is powered off.

This lamp is designed to operate at two wattages on standard high-pressure mercury vapour ballasts. 360w when the voltage tap is set normally and 310w when the ballast tap is set to 10v above the average supply voltage.
I measured 3.7a at 105.5v when my ballast was being fed exactly 240v. Since the ballast that I am using only has 230 or 240v taps, I simulated a 250w tap by simply feeding the ballast 10v less on the 240v tap. I measured 3.6a at 100v at that setting.

10,000h
34,000 / 38,000lm
310 / 360w
110 / 120v
3.4 / 3.7a