Energy saving device for a standard fluorescent lamp system

Claim 1

In combination with a rapid-start type ballast for two low-pressure mercury-discharge fluorescent lamps comprising an autotransformer adapted to be connected across an AC energizing source, said lamps connected in series circuit relationship with ballasting capacitor means with the series combination connected across the primary and the secondary of said autotransformer, said lamps each having two contacts at each end thereof connecting to electrodes operatively positioned proximate the ends of said lamps, additional heater windings in transformer relationship with the primary of said autotransformer and connecting to each of said lamp contacts to preheat said lamp electrodes upon energization of said ballast, and a starting capacitor connected in parallel with one of said lamps to facilitiate series-sequence starting of said lamps, the improvement which comprises: a power reducing means included in series relationship with the two contacts at one end of said lamps, said power reducing means comprising switch means which initially upon energization has a low impedance state to permit current flow and then switches to a high impedance state, said switch means comprising a first switch member in series with one of said contacts at said one end of said one lamp, a second switch member connected in series with the other of said contacts at said one end of said one lamp, and a current limiting capacitor means of predetermined capacitance connected in parallel circuit arrangement across one of said switch members, whereby when the circuit is initially energized, said switch means permits preheating of said lamp electrode connecting to said contacts at said one end of said one lamp, and thereafter upon response to current flow said switch means switches and causes the lamp current to pass through said current limiting capacitor means and decrease by a predetermined amount the current through said normally operating lamps.