Forgive my ignorance, but what are the major benefits and liabilities of each design? More to the heart of the matter, what does the
ballast do?
Ballasts are needed to regulate the
current flow through the arc tube of discharge lights. In most cases, ballasts also provide the high
voltage spike needed to ignite these lights as well.
Fast Overview:
Magnetic
Ballast:
1) Large transformer-like core,
power factoring
capacitor, and a Igniter that produces a high
voltage kick to get the light going.
2) Lamp actually "blinks" 120 times per second each time the
voltage crosses 0 volts
3) Limited range of
voltage and frequency input before
unit can not provide the correct conditions to keep the lamp lit.
4) Very heavy
5) Simple design, so there is not much to fail. Been around for 60+ years, in almost every street light out there.
Electronic
Ballast:
1) Converts AC to DC and then back to AC at a very high frequency using solid state components.
2) Fully regulated
circuit can take very wide range of voltages and frequencies while maintaining proper lamp conditions.
3) Due to the high frequency, there is no visible lamp flicker.
4) Due to secondary frequency, the
transformer core can be very small and lightweight.
5) Complicated design which "came of age" after high
voltage transistors became available. (about 20 years)
6) Usually very reliable, but part failure will stop
unit dead.