Patent GB-190501391-A (GB)
Title: Improvements in Controllers for Apparatus Adapted to be Operated by Alternating Currents.
Inventor: JACKSON RAY PHILIP
Filed: 1905-01-24
Granted: 1905-11-30
Abstract: 1391. Jackson, R. P. June 6, 1904, [date applied for under Patents Act, 1901]. Switches. - Relates to means for preventing arcing at the contacts of controllers employed for supplying alternating currents of variable voltage, particularly for use in systems in which the variable voltage is obtained by connecting up to different points on the secondary of a transformer. An auxiliary autotransformer or other transformer is used, and one of the terminals of the working circuits is connected to an intermediate point of the winding of the transformer. An ohmic resistance may be employed in parallel with the auxiliary transformer. Fig. 1 shows one arrangement, in which a generator 1 supplies a translating device 7 through an auto-transformer 2 and the voltage impressed on the translating device can be varied by moving the contacts 10, 11. One terminal of the translating device 7 is connected to one end of the auto-transformer, and the other to the middle point 19 of an auxiliary auto-transformer connected between the two contacts 10, 11. A resistance 13 is connected between the contacts, and its middle point is also connected to the point 19. In this arrangement, the voltage of the point 19 is intermediate between that of the contacts 121, 122. To increase the voltage, one of the contacts 10 or 11, preferably 10, is moved to the next contact 123, the mutual actions of the windings 16, 17 preventing arcing. To reduce the voltage, the contact 11 is moved back to the contact 12, the contacts 10,11 thus alternately engaging contacts of higher and lower potential. Fig. 2 shows the arrangement applied to a controller, the contact-segments 22, 29, &c. being connected alternately tu the upper contacts 21, 211 and the lower contacts 24, 244. Movement of the controller drum through the positions A ... G successively cuts in sections of the transformer 2, and increases the voltage. In the final position G, the resistance 13 is cut out. In the modified arrangement shown in Fig. 3, the auxiliary transformer 14 has a primary winding 31 and a secondary 32. The controller has auxiliary contacts 181, 182, &c, and 43, 102, &c., which momentarily engage the contact-fingers connected to the sections of the transformer 2 in the movement of the controller to the positions A . . . F. The contacts 181 &c. serve to close the secondary circuit 32 at the moment the contact-fingers are passing from one contact to the next. The contacts 43 &c. serve tc short-circuit momentarily the sections of the tiansformer 2. In another modification, the middle points of the windings 31, 32 are connected to the work circuit. In the arrangement shown in Fig. 5, the auxiliary transformer 14 has two primary windings 311, 312 and one secondary 32. The controller has sets of contacts 211, 212, &c, and 231, 232, &c. which make momentary contact when the controller is moved from one position to the next. The contacts 211 &c. change the connexion of the.primary windings, and the contacts 231 &c. serve to close the secondary circuit.