How do your HPS lamps react to a power failure?

HPS LAMPS: HOW TYPICAL IGNITION WORKS

High Pressure Sodium lamps are commonly named High Discharge Lamps. Generally, it is not possible to ignite instantly a cold HPS lamp to full brilliance. In fact, as power is applied, temperature and pressure gradually increase, causing sodium vapor to enter the arc and release light energy. Sometimes, starting the arc takes a few seconds, and the warm-up period is generally about four minutes. During this time, the lamp exhibits different colors as more sodium vapor enters the arc stream.

When started cold, all HPS lamps have different initial lighting output efficiency, but their average time to get 100% on nominal luminous flux is approximately the same.

WHAT HAPPENS TOUGH, IF YOU IGNITE THEM WHEN THEY ARE HOT?

Once HPS lamps are turned off, for instance in case of power failure on site, and you need to turn them on again in a short amount of time (a few seconds), you are in presence of the so-called Hot restrike, which can cause quite a few problems.

While a conventional HPS lamp is in service, if the lamp circuit is turned off below the level needed to sustain the arc discharge, the ions in the arc tube deionize and light output stops. Even if power supply will be back in few seconds, the lamp will not restart immediately.

Indeed, HPS conventional lamps will need some time to cool down before being re-ignited and delivering high lumen performances. This happens because the arc gases are under pressure and the lamp must cool to an extent to reduce the vapor pressure. Only after this process is over, the lamp will be able to restrike. Time lamps require to re-ignite is strongly influenced by the design of the luminaire, since it determines the cooling rate of the lamp. In general, up to 5 to 10 minutes are required.

Hot restrike is a major concern in applications where prolonged lighting interruptions could create unsafe conditions or a manufacturing shutdown.

HOW TO DEAL WITH HOT RESTRIKE?

In order to deal with hot restrike situations, TECHNOR ITALSMEA has studied HOT INSTANT RESTRIKE ballasts, dedicated ballast (or electrical control gears), available upon request, which assure high efficiency warm-up capability of the HPS lamps and consequently immediate re-ignition for safer working conditions.

TECHNOR ITALSMEA has designed reactor ballasts, which in addition act as current limiters and provide lamp wattage regulation. Moreover, they are combined with a capacitor to provide the highest power factor. Reactor ballasts require a higher start-up current than operating current and they are used only when the available line voltage is at least two times greater than the lamp-rated operating voltage. Such HPS reactor ballasts contain a starting circuit that provides the proper pulse voltage for starting the lamp.

MAIN ADVANTAGES:

Warm-up: 80% of luminous flux in 7 SECONDS
Power: available from 50 up to 400W
Application: designed to operate in severe ambient condition, like wet or high humidity field with ambient temperature up to -50°C/+60°C

For more information, do not hesitate to contact us