Abstract: A voltage control load center (10) includes plural modular voltage control transformer circuits (20), and is connected between supply mains (22) and a load (L) including one or more high intensity discharge (HID) lamps. The lamps are started at full line voltage, and after a sufficient operating interval ensuring that the lamps have achieved a sustaining temperature, the operating voltage applied to the lamps is reduced, effecting a considerable savings in energy use, with little or an acceptably small decrease in illumination provided by the lamps. Because the voltage control transformer circuits (20) are modular, voltage control load centers (10) suitable for a variety of differing requirements may be quickly, easily, and inexpensively fabricated and installed without the need for the conventional requirement of a custom (i.e., application specific) transformer design and fabrication, which conventional requirements are both time and labor intensive.

Abstract: An improved apparatus and method for control of discharge lighting, such as HID (high intensity discharge) lighting, effects full-voltage start up of the lighting, and sustained operation of the lighting at a reduced voltage after a selected and variable start-up phase or interval. The apparatus includes an auto transformer having a primary winding and a secondary winding. The primary winding is always in series with the load, but may be shorted to connect full line voltage from the line to the load. When the primary winding is not shorted, the secondary winding is connected to the load also, so that reduced voltage is provided to the load. A thermal analog device simulates the warm up time constant of the HID lighting unit, so that the reduction in operating voltage to the HID lighting unit is effected only after this lighting unit has achieved a sufficiently high temperature to sustain operation at a reduced operating voltage.