Advance Transformer Co. LI551H4 Lamp Ignitor LI551H4

LI551H4 is a round, black ballast ignitor from Philips Advance designed for 35–150 W high‑pressure sodium lamps and to be used with compatible core‑and‑coil HID ballasts. The compact round housing measures about 1-1/4 inches in diameter and 2-1/2 inches in length, and it operates on 120–277 VAC to deliver the ignition pulse required to strike the lamp. The ignitor supports a lamp‑to‑ignitor distance of up to 2 feet, guiding fixture layout where the lamp is within reach of the ballast. It is specified for HID systems using 35–150 W HPS lamps, and its round‑case design is part of the LI551H4 family of ignition components from Advance Ballast. Used with a compatible ballast, this LI551H4 provides the ignition energy needed to reliably start high‑pressure sodium lighting in round‑case configurations.