China manufacturer of magnetic ballasts for metal halide flood lights & hps flood lights

James offers High Intensity Discharge ballasts for mercury, probe start metal halide, pulse 

start metal halide and high pressure sodium lamps. Standard metal halide lamps or probe 

start metal halide over 150 watts, like fluorescent, are electric discharge lamps and require an 

open circuit voltage of nearly two times the operating voltage to the initiate the arc between 

the two electrodes in the arc tube. High pressure sodium, pulse start metal halide and probe 

start metal halide lamps 150 watts or less require an ignitor to initiate the high voltage to 

start the lamps. The ballasts provide the starting voltage with the igniter, where required, and 

provides stability for the lamp. HID lamps have negative impedance characteristics and would 

draw current until destruction unless a ballast was in place to regulate the current.

HID lamps take several minutes to warm-up and reach full light output. If power is interrupted 

between the lamp and the ballast, the arc will extinguish and lamp will go out. The lamp must 

cool down and reduce the vapor pressure before it will re-start.

The most common HID ballasts are the core and coil and is used in 90% of the fixture 

applications. Core and coil ballasts consist of one, two or three copper (or aluminum) coils on a 

core of electrical-grade steel laminations. HID ballasts are classified by the kind of circuit they 

use: Reactor (R), High Reactance autotransformer (HX), Constant Wattage Autotransformer 

(CWA), Regulated lag (Reg Lag) or Electronic. HID ballast are also classified as high power factor 

(HPF) or normal power factor (NPF). 

To correct the high current draw associated with reactor and high reactance ballasts, and to provide a greater level of lamp wattage regulation, the 2-coil Constant Wattage Autotransformer (CWA ballast, also referred to as a "Peak Lead Autotransformer") was developed. It is the most commonly used ballast circuit for medium and high wattage (175 - 2000W) applications and typically represents the best compromise between cost and performance. The CWA is a high power factor ballast utilizing a capacitor in series with the lamp rather than across the input. The capacitor works with the core-and-coil to set and regulate the lamp current to the prescribed level.

 

The CWA ballast provides for greatly improved lamp wattage regulation over reactor and high reactance circuits. A +/- 10% line voltage variation will result in a +/- 10% change in lamp wattage for metal halide. The metal halide and high pressure sodium ballasts also incorporate wave shaping of the open circuit voltage to provide a higher peak voltage than a normal sine wave. This peak voltage (along with the ignitor when used) is used to start the lamp and control the lamp current crest factor (typically 1.60 - 1.65).

 

With the CWA ballast, input current during lamp starting or open circuit conditions does not exceed the input current when the lamp is stabilized. CWA ballasts are engineered to tolerate 25-30% drops in line voltage before the lamp extinguishes (lamp dropout), thus reducing accidental lamp outages.