Method and apparatus for operating a gas discharge tube

Claim 2

In a circuit for starting and subsequently operating a gas discharge tube from an AC source, the combination of an autotransformer comprising a first and second series connected coil, said first coil being the primary winding, said first and second series connected coils being the secondary winding, and said second coil being adapted for operation as an inductive ballast for said tube during operation thereof from said AC source after starting, switch means interPosed between said first and second coils for enabling transformer action therebetween upon the application thereto of current from said AC source to produce a sufficient potential across said secondary winding for starting said tube, said switch means inhibiting said transformer action following arc discharge within said tube, whereupon said second coil acts as said inductive ballast in series with said tube during operation thereof from said AC source after starting, said autotransformer possessing a predetermined value of leakage inductance for coacting with stray capacitance in said circuit to generate transient high-frequency currents in said secondary winding to lower said requisite starting potential.

Claim 3

The combination according to claim 1 wherein said first and second coils are wound on one limb of a laminated core stack forming a magnetic circuit.

Claim 4

The combination according to claim 1 wherein said switch means comprises an electromagnetic relay having a relay coil connected across said secondary winding capable of drawing sufficient current therefrom for operating relay contacts connected between said first and second coils, said contacts remaining closed during the starting operation for enabling said transformer action, and being opened by said relay coil following arc discharge within said tube.

Claim 5

The combination according to claim 2 wherein said switch means comprises a magnetic shunt in said magnetic circuit including additional laminations interposed between said first and second coils to impede substantially the current flow therebetween for inhibiting said transformer action following arc discharge within said tube, the arrangement being such that said first and second coils coact in said transformer action during the starting operation, said second coil acting as said inductive ballast following said arc discharge.

Claim 6

The combination according to claim 2 wherein nonmagnetic gaps are provided in said magnetic circuit having a width related to a requisite inductance for said inductive ballast to suit the operating characteristics of said tube.

Claim 7

The combination according to claim 5 wherein said nonmagnetic gaps are adjustable airgaps.

Claim 8

Apparatus for starting and subsequently operating a gas discharge tube from an AC source comprising an autotransformer consisting of a first and a second series connected coil, said first coil being the primary winding, said first and second series connected coils being the secondary winding and said second coil being adapted for operation as an inductive ballast for said tube during operation thereof from said AC source after starting, switch means interposed between said first and second coils for enabling transformer action therebetween upon the application thereto of current from said AC source to produce a sufficient potential across said secondary winding for starting said tube, said switch means inhibiting said transformer action following arc discharge within said tube whereupon said second coil acts as said inductive ballast in series with said tube during operation thereof from said AC source after starting, a relay coil connected across said secondary winding for automatically opening and closing said switch means respectively before and after said arc discharge within said tube, connecting means adapted for connecting one end of said primary winding and said switch means to said AC source, and further connecting means adapted for connecting said gas discharge tube across said secondary winding, said autotransformer possessing a predetermined value of leakage inductance for coacting with stray capacitance in said apparatus to generate transient high-frequency currents in said secondary winding to lower said requisite starting potential.

Claim 9

Apparatus for starting and subsequently operating a gas discharge tube from an AC source comprising an autotransformer consisting of a first and a second series connected coil, said first coil being the primary winding, said first and second series connected coils being the secondary winding and said second coil being adapted for operation as an inductive ballast for said tube during operation thereof from said AC source after starting, switch means interposed between said first and second coils for enabling transformer action therebetween upon the application thereto of current from said AC source to produce a sufficient potential across said secondary winding for starting said tube, said switch means inhibiting said transformer action following arc discharge within said tube whereupon said second coil acts as said inductive ballast in series with said tube during operation thereof from said AC source after starting, a relay coil connected across said secondary winding for automatically opening and closing said switch means respectively before and after said arc discharge within said tube, connecting means adapted for connecting one end of said primary winding and said switch means to said AC source, and further connecting means adapted for connecting said gas discharge tube across said secondary winding, said autotransformer possessing a predetermined value of leakage inductance for coacting with stray capacitance in said apparatus to generate transient high-frequency currents in said secondary winding to lower said requisite starting potential.

Claim 10

The apparatus according to claim 7 wherein said first and second coils are wound on one limb of a laminated core stack forming a magnetic circuit, said stack comprising a plurality of E-shaped laminations, and a corresponding plurality of laminaTions arranged across and closing the open side of the E-shaped laminations, said first and second coils being wound on the central limbs of the E-shaped laminations.

Claim 11

The apparatus according to claim 8 wherein nonmagnetic gaps are provided between the ends of the parallel limbs of the E-shaped laminations and said closure laminations, said gaps being of a width to suit the operating characteristics of said tube when connected across said secondary winding such that said second coil has the required inductance for said inductive ballast.

Claim 12

The apparatus according to claim 9 wherein said gaps are adjustable airgaps.

Claim 13

Apparatus for starting and subsequently operating a gas discharge tube from an AC source comprising an autotransformer consisting of a first and a second series connected coil, said first coil being the primary winding, said first and second series connected coils being the secondary winding, and said second coil being adapted for operation as an inductive ballast for said tube during operation thereof from said AC source after starting, a laminated core stack forming a magnetic circuit, said first and second coils being wound one above the other on one limb of said stack, a magnetic shunt for said magnetic circuit interposed between said first and second coils enabling transformer action to take place between said first and second coils upon application to said first coil of current from said AC source to produce a sufficient potential across said secondary winding for starting said tube, said shunt inhibiting said transformer action following arc discharge within said tube whereupon said second coil acts as said inductive ballast in series with said tube during operation thereof from said AC source after starting, connecting means adapted for connecting said primary winding to an alternating current supply, and further connecting means adapted for connecting said gas discharge tube across said secondary winding, said autotransformer possessing a predetermined value of leakage inductance for coacting with stray capacitance in said apparatus to generate transient radiofrequency currents in said secondary winding to lower said requisite starting potential.

Claim 14

Apparatus for starting and subsequently operating a gas discharge tube from an AC source comprising an autotransformer consisting of a first and a second series connected coil, said first coil being the primary winding, said first and second series connected coils being the secondary winding, and said second coil being adapted for operation as an inductive ballast for said tube during operation thereof from said AC source after starting, a laminated core stack forming a magnetic circuit, said first and second coils being wound one above the other on one limb of said stack, a magnetic shunt for said magnetic circuit interposed between said first and second coils enabling transformer action to take place between said first and second coils upon application to said first coil of current from said AC source to produce a sufficient potential across said secondary winding for starting said tube, said shunt inhibiting said transformer action following arc discharge within said tube whereupon said second coil acts as said inductive ballast in series with said tube during operation thereof from said AC source after starting, connecting means adapted for connecting said primary winding to an alternating current supply, and further connecting means adapted for connecting said gas discharge tube across said secondary winding, said autotransformer possessing a predetermined value of leakage inductance for coacting with stray capacitance in said apparatus to generate transient radiofrequency currents in said secondary winding to lower said requisite starting potential.

Claim 15

The apparatus according to claim 11 wherein said laminated core stack comprises a plurality of E-shaped laminations and a corresponding plurality of laminations arranged across and closing the open side of the E-shaped laminations, said first and second coils being wound on the central limbs of the E-shaped laminations, and said magnetic shunt comprises a plurality of laminations, for shunting said magnetic circuit between said first and second coils.

Claim 16

The apparatus according to claim 12 wherein nonmagnetic gaps are provided between the ends of the parallel limbs of the E-shaped laminations and said closure laminations, said gaps being of a width to suit the operating characteristics of the tube when connected across the secondary winding such that said second coil has the required inductance for said inductive ballast.

Claim 17

The apparatus according to claim 13 wherein said gaps are adjustable airgaps.

Claim 20

The apparatus according to claim 15 wherein said variable current limiting means comprises a resistance in series with said tube and gate controlled rectifying means possessing both forward and reverse rectifying characteristics, said rectifying means being provided for shunting said resistor whereby said light output may be varied.

Claim 21

The apparatus according to claim 16 wherein said switch means comprises an electromagnetic relay having a relay coil connected across said secondary winding capable of drawing sufficient current therefrom for operating relay contacts connected between said first and second coils, said contacts remaining closed during the starting operation for enabling said transformer action, and being opened by said relay coil following arc discharge within said tube.

Claim 22

The apparatus according to claim 16 wherein said first and second coils are wound on one limb of a core stack forming a magnetic circuit, said switch means comprising a magnetic shunt interposed between said first and second coils to impede substantially the current flow therebetween for inhibiting said transformer action following arc discharge within said tube, the arrangement being such that the first and second coils coact in said transformer action during the starting operation, and said second coil acting as said inductive ballast following said arc discharge.

Claim 23

The apparatus according to claim 15 wherein said first and second coils are wound on one limb of a laminated core stack forming a magnetic circuit, said magnetic circuit being provided with adjustable airgaps for varying the inductance of said inductive ballast to suit the operating characteristics of said tube.