||SPX EcoArc lamps were introduced in 1998 to offer a performance upgrade vs Sylvania's ULX / SHX Penning-start retrofits for mercury lamps. Those suffered relatively short lifetime owing to their rapid voltage rise during life, and despite the improvement in efficacy above mercury lamps, this was limited owing to the losses associated with the neon-argon fill that was necessary for easy ignition.
Sodium lamps can save energy on mercury ballasts due to their reduced power factor, and the shape of the ballast curve allows further savings by operating at either lower or higher lamp voltages. Most HPS retrofits use lower voltage to allow for voltage rise during life, however the SPX lamps were the first to shift to higher voltages up to 165V, made possible thanks to the their novel arc tube which operates in the mercury-unsaturated and sodium-saturated regime. The amalgam dose is considerably reduced, such that all the mercury and virtually all of the sodium is vaporised when in operation. Such lamps are characterised by a stable voltage through life, which permits the unusually high voltage.
The arc tube is xenon-filled for high efficacy and starting is facilitated by an ignition antenna, biased by a glowbottle in this low wattage lamp, or by an FEC + Sidac ignitor in the base of the larger versions. To limit the rate of sodium loss, the arc tube is made of NGK's superior G-40 ceramic, and the electrode emitter is Sylvania's low-reactivity BSY2 mix. The range originally comprised 98W, 190W and 295W ratings to replace 125W, 250W and 400W mercury. Following a design tweak to limit the voltage peaks during run-up, this smallest model was re-rated to 69/108W in 2001, so as to replace both 80W and 125W mercury lamps.