This guide is prepared to assist electricians with normal routine maintenance and to help them understand the operation of different lamp sources and electrical systems.

Caution: High voltages, currents, and temperatures are required to operate gas discharge lamps. Shock and burn hazards exist, and testing or evaluating fixtures or compo-nents should be done by qualified individ-uals only.

Light Sources:

Fluorescent
Mercury Vapor (MV)
Metal Halide (MH)
High Pressure Sodium (HPS)

Lamps

Fluorescent lamps come in many sizes, shapes and colors. This lamp source can provide numerous advantages, depending on the needs and requirements of end users. These lamps are generally used when low mounting heights and quiet operation are required. Note that many new, more efficient lamps and electronic ballasts offer the customer many energy saving opportunities.

Mercury Vapor lamps were the first to be developed in the family of high intensity discharge (HID) lamps. Their advantage is that they offer long life. Their disadvantages are poor color rendition, poor lumen maintenance, and low efficiency.

MH lamps are similar to MV lamps in design and operation. Their lumen output is double that of MV lamps of the same wattage. MH lamps are used in installations that require high efficiency, and white light. Lamp life historically has been less than MV and HPS, however new MH systems are now changing this by providing excellent life, lumen maintenance and color control.

A. HPS lamps offer long life and more lumens per watt than MV or MH sources. HPS lamps emit a pale amber color compared to other whiter light sources. Energy savings is the main HPS advantage. New high-xenon HPS lamps offer even higher LPW, longer life and improved lumen maintenance.

Ballasts

All HID light sources require some form of ballast because:

Most require a starting voltage that is higher than the line voltage.

They all have a characteristic known as negative resistance. This means that once the arc is initiated, the lamp’s resistance continually decreases as current increases. For all practical purposes, the lamp becomes a short circuit. The ballast limits and controls the current wave form through the lamp. They provide voltage transformation to allow the use of many line voltages.

There are many different types of ballasts used with different lamps. Within a lamp type, ballasts vary in lamp operating wattage and regulation caused by changes in line voltage and lamp voltage. Better regulation and control normally results in higher initial cost, but may greatly improve operating characteristics and overall performance.

Capacitors

Capacitors are used for power factor correction or as current regulation devices which provide the control necessary to ensure proper lamp and ballast operation. Different wattages, voltages, and ballast types require a variety of different capacitors. The ballast ID label specifies the microfarad and voltage rating required for proper operation. If the capacitor is incorrectly wired, improper operation of the fixture as well as other component failures could result.

Ignitors/Starters

These devices are utilized to provide the proper voltage and energy to start the lamp. They are predominantly used with HPS lamps as well as some Metal Halide and Fluorescent systems.