HID BALLAST TECHNOLOGIES
This is the most common and simplest type of HID ballast available. The only purpose of this type of ballast is to limit the current being fed to the lamp. Reactor ballasts can only be used when the line voltage is greater than the lamp starting voltage.
Reactors are the most compact, economical and most efficient ballasts because their job is to perform only one function. However, reactor ballasts are not recommended where power fluctuations are greater than +/- 5% because they offer little regulation capability.
By adding a capacitor (typically dry type) across the line, the power factor of the reactor system can be increased to be better than 90%. Adding the capacitor drops the required input current for starting and operating conditions down to as low as 50% lower than is needed for the normal power factor reactor system. This allows for more lamps and ballasts per circuit using the same wire gauge as with NPF systems.
AUTO-LAG AUTOTRANSFORMER (HX-NPF)
In this type, a transformer is used in conjunction with the reactor to raise line voltage that is below the minimum lamp starting voltage. Such a function is performed by combining a secondary winding with a primary winding to form a single phase autotransformer.
This circuit has the advantages of a normal power factor reactor, with a power factor of approximately 50%.
AUTO-LAG AUTOTRANSFORMER (HX-HPF)
In this type, the addition of a capacitor to the primary circuit makes it possible for an autotransformer ballast to provide a high power factor.
The high power factor autotransformer is usually designed with an extra capacitor winding within its copper windings in order to provide a more economical and efficient system. The ballast’s power factor can be increased to about 90% by combining the extended windings with the capacitor. The input current is reduced, as in the high power factor reactor. Lamp performance and regulation are also the same as a reactor ballast at +/- 5%.
CONSTANT WATTAGE AUTOTRANSFORMER (CWA)
The constant wattage autotransformer HID ballast type should be used where a stabilized light output is required.
CWA is an HID ballast type that comes in a fairly small economical size, yet still provides a reasonable degree of regulation. It also offers the advantage of a high power factor, low line extinguishing voltage, and line starting currents that are lower than operating currents.
Unlike the high power factor auto-transformer (HX-HPF), which uses a capacitor as a parallel component, the capacitor on a CWA ballast type is used in series with the lamp. This provides the lamp with a more stable wattage when voltage on the branch circuit fluctuates.
The capacitor is referred to as a lead circuit when, as in the case of the CWA ballast, it performs an important ballasting function.
CONSTANT WATTAGE ISOLATED (CWI)
When electrical isolation for the lamp power regulation is required, CWI ballasts are recommended because the primary and secondary coils are not connected. When the secondary coil does not share a portion of the primary coil, more efficient shunting of the ballast core flux can be achieved by the shunts of the ballast. This provides better lamp power regulation than with CWA ballasts. Electrical isolation is an important consideration when line to line supply voltages are used. The isolation allows the lamp screw shell to be safely grounded, and not be a shock hazard when the lamp is removed.
CWI designs eliminate the need for time delay relays, oversize circuit breakers, and heavier wiring (which is required by reactor and lag autotransformer ballasts for the same number of fixtures per circuit).
Lamp wattage and consequent light output from the lamps is maintained in spite of line voltage variations as great as 13% from nominal. This ensures reliable starting and operation within lamp specifications, and guaranteeing full lamp life and optimum performance.
Lamp extinguishing due to line voltage dips is improved over the previous circuit types. The CWI circuit will hold the lamp in operation even if supply voltage dips to 25 % below normal.
MAGNETIC REGULATOR (MAG-REG)
The magnetic regulator ballast is a three isolated coil ballast. The third coil is used to connect to a capacitor which resonates with the coil providing a stable magnetic flux in the ballast core as well as power factor correction.
The resonating current, and flux of the third coil produce significantly higher ballast losses, cost and larger size than other ballast types. Lamp extinguishing due to line voltage dips is virtually eliminated because the Mag-Reg circuit will hold the lamp in operation even if supply voltage dips to 30 % below normal.
Ignitors are intended to function with specific ballasts. Always check ballast and ignitor compatibility prior to installation. Ignitors should always be installed near the ballast but not on the ballast. A lighting system which calls for an ignitor must come with a pulse rated lamp socket in order to avoid voltage breakdown and arcing, caused by the high voltage ignitor pulse.
The capacitor is a very important part of the ballast and its function is often overlooked or forgotten. Both oil-filled and dry-film capacitors are used with ballasts, neither of which contain PCB’s.