Choosing the Right Ballast

Fifteen years ago, matching ballasts and metal halide lamps was very simple because there were four basic lamp types and associated ballasts (175W, 250W, 400W, and 1000W). As metal halide usage increased, the need for specialty lamps and control gear became apparent. Metal halide users now demand additional qualities such as longer lamp life, higher lumen output, quicker starting, and most importantly better energy efficiency. To achieve these benefits, ballasts and lamps must be compatible. See our Specification Sheets to ensure that this compatibility is achieved. The following are the ballasts now commonly used.

This was formerly the "standard" and is still the most common type of ballast used for standard metal halide lamps (175W and higher). Lamps with starter electrodes are used with this ballast, so no ignitor is needed. The ballast can transform (increase) voltage so lower line voltages (120V) can be used. They use a capacitor and have a high power factor (90%). This ballast can tolerate a line voltage drop of 30% without the lamp extinguishing.

Reactor Ballast (R)

This is the simplest ballast and is often referred to as a lag or choke. It is used when the line voltage is high enough to start lamps (240 or 277V). It has low power factor (50%) unless it is corrected with a capacitor. These ballasts have very poor regulation of the secondary (lamp) voltage.

High Reactance Auto Transformer (HX)

This ballast is the most common type used today for low wattage (below 100W) lamps and uses an ignitor in these cases. This is also a reactor or lag type ballast with low power factor unless a capacitor is used (correctable to 90%). This ballast can transform (increase) input voltage so it is high enough to start lamps.

Regulated Lag Ballasts (Reg. Lag)

Until recently, these ballasts were primarily used for HPS lamps. Now they have been modified to operate Venture’s Uni-Form formed body pulse start lamps. This is a premium ballast with excellent regulation and is used in conjunction with an ignitor. The Uni-Form pulse start lamps designed for this system generally have extended life and higher lumen output. These ballasts can tolerate a line voltage drop of 50% without the lamps extinguishing.

Instant Restrike System (IS)

This system typically uses a specially wired CWA ballast and a high voltage ignitor (20,000+V). They are used to instantly restart lamps after a momentary power failure. These require special lamps and a fixture with electromechanical interlocks.

Controlled Current Reactor

These new ballasts employ reactor circuitry that can reduce "typical" ballast losses by about 50%. For example, a 150 watt ballast will only have 17 watts loss compared to 35-45 watts loss in standard 175W or 150W ballasts. They are designed to run on 277 input volts and use an ignitor to start the lamp. When used with Uni-Form pulse start lamps, the combined energy savings can be over 25%. This is accomplished with little or no light loss.

Electronic Ballasts

Other ballast types utilize an iron core and copper wire windings in order to operate. Electronic ballasts use component circuitry to start and sustain lamps. This affords them the benefit of greatly reduced size and weight. Fixtures designed for these ballasts are small enough to be used in any application. Electronic ballasts typically operate the lamps on DC voltage and have negligible ballast losses. The DC voltage extends life and decreases lumen depreciation.

When choosing a ballast for H.I.D. lamps, the options are a luminaire that has an integrally-mounted ballast, or a fixture (reflector, diffuser and lampholder assembly) for use with a remote ballast. The following points show some of the advantages of both options.

Integral Ballasts (Core & Coil)

Integral ballasts, or "core and coil" ballasts, must be suitably mounted and enclosed in the luminaire to pass CSA/UL requirements for electrical safety and operating temperature. Venture technical experts work in close liaison with fixture manufacturers, who offer a wide variety of H.I.D. lighting alternatives.

Some advantages of integral ballasts are:

• ballast is pre-wired to reduce installation cost

• components of fixtures are delivered to the job site together

• the ballast is easily located when trouble-shooting the lighting system

Remote Ballasts

Indoor remote ballasts are intended specifically for areas protected from the weather. The design allows for operation in ambient temperatures of 40°C or less. The ballasts must be mounted in areas where the air will circulate freely around the enclosure. They can be mounted vertically or horizontally. Designs for 60°C high ambient temperature are available

Outdoor remote ballasts have deep drawn, one-piece cases with aluminum spun-on covers and finish, except 1000 W. Neoprene gaskets placed between the case and the cover are roll-clamped under hydraulic pressure. All wiring connections are made to neoprene-insulated leads, which are inserted through a waterproof plug. Outdoor ballasts can be used at a pole base, on a cross arm, or mounted on the top of a pole. The ballasts are recommended for operation in ambient temperatures up to a maximum of 25°C (77°F).

Remote ballasts have several advantages:

• Remote mounting can be done to keep a ballast cool for lighting in high-ambient temperature areas.

• When fixture location is difficult to reach, the ballast can be mounted near the floor or a balcony.

• When low levels of sound are important, the ballast can be mounted outside an occupied area.