A "ballast" used for electrical elements, "discharge lamps" in this case, is a current limiter, because in this type of lamps, which work by electric crackling between metallic particles in gaseous suspension, the amperage tends to become infinite with the heating, hence if the device accepts 150 w, limits the current for that value, therefore, 250 watts, requires more current, that that device will not deliver it to you, it will be useless. I hope I was clear. luck
A "ballast" used for electrical elements, "discharge lamps" in this case, is a current limiter, because in this type of lamps, which work by electric crackling between metallic particles in gaseous suspension, the amperage tends to become infinite with the heating, hence if the device accepts 150 w, limits the current for that value, therefore, 250 watts, requires more current, that that device will not deliver it to you, it will be useless. I hope I was clear. luck