Abstract: An AC ferroresonant transformer includes a core having a closed loop path and a magnetic shunt assembly extending between portions of the core. A primary winding, a secondary winding and a tertiary winding are disposed on the core to link with magnetic flux in the core and the magnetic shunt. The tertiary winding includes terminals that are electrically isolated from the secondary winding. A first aspect of the present invention includes a tank capacitor connected to the tertiary terminals to form two LC circuits wherein a first LC circuit is a resonant circuit and a second LC circuit is a filtering circuit. Another aspect of the present invention is a method of operating an AC ferroresonant transformer proximate a knee of a B-H curve of the core, at minimal line voltage and full load, to reduce the generated harmonics.

Abstract: A dry film curing machine utilizes ultraviolet lamps mounted in reflectors, which are positioned on opposite sides of a mesh or open type conveyor belt carrying the film to provide radiation for drying. The lamps are controlled by a circuit that regulates the intensity of the ultraviolet lamps to a set level as the lamp ages. The control is effective even though the arc in the lamp may deflect as the lamp warps under temperature differentials. A sensor is mounted in a housing and is positioned adjacent the lamp. The sensor housing eliminates reflected ultraviolet light from striking the sensor, to eliminate erroneous input signals. The sensor provides a signal that is directly proportional to ultraviolet lamp intensity and this signal is used to adjust the power (primarily the current) to the lamp through a microprocessor controlled power source to maintain the UV intensity at the set level.