It has been over 30 years since I went to engineering school, but I think I still remember enough of what I learned to know that statement is impossible. Voltage is a constant. You can't use more or less than what is there. If you meant "one third the current" that might make sense, since Ohm's Law states that current is inversely proportional to resistance (I = E/R). To use one third the current, the resistive value of the element and ballast would have to be 3x greater than the light source it replaced.