Multiple lighting level ballast for fluorescent lamps

Claim 2

A ballast apparatus for starting and operating at least one fluorescent lamp comprising: a high leakage reactance transformer having a primary winding and a secondary winding; capacitive reactance means including a first number of series connected capacitors, said first number being greater than one, in series-circuit relationship with said transformer and having a capacitive reactance value to cause a leading current to flow therethrough; means including electrical leads for extending connections from said transformer and capacitive reactance means to the lamp to form a series circuit therewith when connected thereto; and switching means coupled to said first number of capacitive reactance means and having a second number of selectable switch positions, said second number being one more than said first number, the fluorescent light level being selectively variable to any one of a second number of light levels when connected as aforesaid whereby the number of light levels which may be obtained is one greater than the number of said series capacitors.

Claim 3

The ballast of claim 1 wherein said capacitive reactance means include first and second series-connected capacitors, and said switch means include a three-position switch with a center arm movable to a first and second position to contact first and second contacts respectively, and a third position without electrical connection to either capacitor, said center arm being coupled to the junction of said first and second series-connected capacitors, said first contact being coupled to a second end of said first capacitor and said second contact being coupled to a second end of said second capacitor whereby one or the other of said first and second capacitors is short-circuited by said switch means in one of said first and second positions.

Claim 4

The ballast of claim 1 wherein said primary and secondary windings are in series-circuit relation forming an autotransformer.

Claim 5

The ballast of claim 1 wherein said first number is two and said switch means are operative to selectively couple both, one or the other of said capacitors in series-circuit relationship with said transformer.

Claim 6

The ballast of claim 4 wherein said switch means comprise a three-position switch.

Claim 7

A ballast apparatus for starting and operating at least a pair of fluorescent lamps wherein the lamps are arranged in series-circuit relation including in combination: first capacitive reactance means comprising a starting capacitor coupled in parallel with one of said fluorescent lamps; a high reactance transformer having a primary and secondary winding forming an autotransformer configuration; second capactive reactance means including first and second series coupled capacitors in series-circuit relationship with said autotransformer and adapted to be coupled in series-circuit relationship with said fluorescent lamps, said second capacitive reactance means having a capacitive reactance of such value related to the inductive reactance of the circuit to cause a leading current to flow therethrough; and switching means arranged in connection with said second capacitive reactance means and operative selectively to couple both, one or the other of said first and second series coupled capacitors in seriEs-circuit relationship with said autotransformer whereby the fluorescent light level is varied to any one of three different conditions depending upon the coupling.

Claim 8

A ballast apparatus for starting and operating at least a pair of fluorescent lamps wherein the lamps are arranged in series-circuit relation including in combination: first capacitive reactance means comprising a starting capacitor coupled in parallel with one of said fluorescent lamps; a high reactance transformer having a primary and secondary winding forming an autotransformer configuration; second capactive reactance means including first and second series coupled capacitors in series-circuit relationship with said autotransformer and adapted to be coupled in series-circuit relationship with said fluorescent lamps, said second capacitive reactance means having a capacitive reactance of such value related to the inductive reactance of the circuit to cause a leading current to flow therethrough; and switching means arranged in connection with said second capacitive reactance means and operative selectively to couple both, one or the other of said first and second series coupled capacitors in seriEs-circuit relationship with said autotransformer whereby the fluorescent light level is varied to any one of three different conditions depending upon the coupling.

Claim 9

The ballast of claim 6 wherein said switch means include a three-position switch having a center arm movable to a first and second position to contact first and second contacts respectively and a third position, said center arm being coupled to the junction of said first and second series-connected capacitors, said first contact being coupled to a second end of said first capacitor and said second contact being coupled to a second end of said second capacitor.

Claim 10

The ballast of claim 6 wherein said primary and secondary windings are coupled in series with one another and said second capacitive reactance means, said primary winding being coupled to a source of alternating current.

Claim 11

The ballast of claim 6 wherein said switch means are a three-position switch.