| Because any HID lamp presents a "negative resistance", a ballast is necessary to limit the current through the lamp. A filament lamp has a fixed wattage, say 100 watts. A HID lamp does not. It is one of the ballasts function to limit the current through the lamp. This is why it did not blow the breaker when the chain hit the lamp base. The ballast held the wattage of the arcs (inside the lamp, and at the lamp base) to 600 watts.
(BTW- I have never heard of a 600 watt HPS lamp in the US. Must be a Canadian standard.)
Andy |