GB1066370A - Improvements relating to inductive apparatus - Google Patents

Abstract

1,066,370. Transformer. FERRANTI Ltd. Feb. 7, 1966 [Nov. 26, 1964], No. 48057/64. Heading H1T. [Also in Division H3] The coupling between the two windings of an inductive apparatus (e.g. transformer) is controlled by a third winding which saturates the ferromagnetic screen on which it is toroidally wound and which screen separates the two main windings. A cylindrical laminated limb 10 (Fig. 2) carries the first winding 12 and has its part circular end flanges 11 shaped to accommodate a control winding 14 which is wound toroidally on a laminated ferromagnetic cylindrical screen 13 in the two opposite spaces not in magnetic contact with the core 10. The second winding 15 is wound around the screen 13 over the winding 14. The control winding 14 is energized with direct current to produce a magnetic field in the screen 13 perpendicular to the fields produced by either main winding 12, 15 whereby the screen may be saturated to regulate the coupling between the windings. The iron core 10 may be replaced by a three-link core in magnetic contact with the screen 13 to provide a return flux path, with the outer links passing outside winding 15. An alternative arrangement includes a second screen (16) (Fig. 3, not shown), placed around the outer winding 15 and provided with a second control winding (17) to vary the saturation of the second screen (16). The two screens may be connected such that the saturation of one screen increases while the other decreases. When the primary and secondary windings are divided into seriesconnected sections and interleaved, a separate screen may be located between each section of the primary and the adjacent sections of the secondary. The arrangement may form an electric switch if the primary winding has a high impedance and is connected into the circuit to be controlled, while the screened secondary winding is made to have a low impedance (e.g. by short-circuiting the winding). When the control winding is energized, the low impedance of the secondary is reflected into the primary to greatly reduce the primary impedance (e.g. stated impedance ratios of 100 to 1).