GB689368A - Improvements in and relating to high frequency transformers - Google Patents

Abstract

689,368. Transformers with inductances. BRITISH THOMSON-HOUSTON CO., Ltd. July 25, 1951 [July 28, 1950], No. 17642/51. Class 38 (ii). A high-frequency electric transformer comprises a unitary body 3 of insulating material, having high dielectric strength and a low loss factor, arranged about and between the primary and secondary windings 1, 2, an axially movable metal cylinder 5 being provided close to the insulating body to form an adjustable short circuited winding. The primary winding 1 is formed of a hollow tube through which a cooling fluid may be passed whilst the secondary winding 2 comprises a single turn of sheet metal the insulating body 3 being formed of a material such as polythene by the Schoop gun process, the body being provided with rounded portions 4 to prevent superficial disruptive discharges. An adjustable copper cylinder 5, axially guided through the bore of the insulating body by rods 5a, forms a movable short-circuited turn in order to vary the coupling between the primary and secondary windings. To provide compensation for the alteration in the transformer reactance which takes place when the coupling is varied, and thus to correct the modulation of the circuit in which the transformer is used, a variable indicator is provided, the winding of which is connected in series with the primary winding of the transformer. The variation of the inductor may be occasioned by the use of a movable core which may be caused to move simultaneously with the cylinder 5. In a further embodiment the inductor may be located in an axial extension of the insulating body in which case the variation in the inductor and in the coupling of the transformer may be effected by the short circuited copper cylinder. A further secondary winding may be associated with the inductor winding to form a transformer having a different ratio to that of the transformer 1, 2, the functions of the transformer and inductor then being interchangeable as desired. A cooling member may be attached to the cylinder 5 which cylinder may be made of two telescoping members to afford adjustment in the length thereof.