26-03-2014, 04:57 PM
Electronic Ballasts for High Intensity Discharge Lamps (HID)
Electronic Ballasts.pdf (Size: 1.35 MB / Downloads: 21)
Advantages of Electronic Technology
. Improves the overall efficiency of low wattage systems.
. A single unit replaces three components: ballast, capacitor and ignitor.
. Protects against voltage and current transients and lamp malfunction (e.g. DC effect near end-of-life).
. Stable light output.
. Stable watt output despite AC line voltage fluctuations.
. Power factor very close to 1.0.
. Lamp-friendly ignition process.
. Perfect square wave lamp current: increases longevity and improves lumen maintenance.
. Option for lamp monitoring and control.
Disadvantages of Electronic Technology
. The benefit of the efficiency of electronic ballasts decreases with rising lamp watt rating.
. Complex product because of complicated operational tasks.
. Sensitivity to high temperatures affects installation options.
. High cost.
. Acoustic resonance when lamp is operated at high frequency (Eltam's HID electronic ballast operates the lamp at low frequency).
Contribution of the Electronic Ballast to Lamp Longevity and Lumen Maintenance
. Lowers electrode meltback and shortens the glow stage through good control of the ignition process.
. Lamp current is square wave at low frequency.
. Faster lamp polarity inversions (minimal intervals at low current values).
. No reignition overvoltage required during steady state operation.
Operation Environment
. Actual working temperature is lower than ballast rated maximum.
. Electromagnetic compatibility standards (Surge, EMI, Harmonics content) are met.
. Input current is undistorted.
. Ballast inrush current and its effect upon the line overcurrent protection.
. Automatic ballast shut off upon line or lamp malfunction.