Abridgment of the rectification of alternating currents with steel enclosed mercury arc power rectifiers and their auxiliary devices

Recently many publications have been issued on mercury arc rectifier installations in this country and in Europe, as well as on the theory of their voltage and current performances. Nevertheless, it seemed that it might be of interest to give a condensed paper dealing with the most important theoretical treatments, as well as a description of a steel enclosed rectifier of modern design. The fundamental theory of these rectifiers is discussed, touching only slightly upon the physical phenomena, but treating particularly of the theory involved in the practical applications. The effects of various factors on the rectifier characteristics and operation are dealt with, and the methods used for calculating the relations of voltages, currents, transformer ratings, etc., are given and tabulated. Moreover, there are mentioned the latest developments of the rectifier proper, as well as the auxiliary devices. Included in this is the design of the transformers from a mechanical point of view, making them rigid enough to stand the mechanical stresses forced upon the windings under abnormal operating conditions; and from an electrical point of view, giving the characteristics of connections such as zig-zag windings, special polyphase windings, and the introduction of reactance absorption coils in the neutral connections of the transformer. Special attention is paid also to the anodes and their cooling equipment, and to the seals, several ingenious points being brought out in their construction. The vacuum question also is considered one of the most important, not only from the standpoint of producing and maintaining the vacuum, but also from the standpoint of measuring it. The importance of properly measuring the degree of vacuum, as well as the amount of mercury and other vapor present in the cylinder, is brought out, since it was found that the well-known devices for measuring a vacuum, such as McLeod´s vacuum gage, did not give the actual conditions existent in the cylinder,- but only a relative indication, namely, the pressure of the perfect gases. A new vacuum-measuring gage of novel design, which only very recently has been developed to its present state of perfection, is described in detail and its operation explained. This gage makes it possible to measure and record the absolute pressure of the gases and vapors contained in the rectifier cylinder. The preparation of the rectifiers for service and their operation are described, and special attention is given to the numerous advantages secured by the use of rectifiers in substations. To simplify operation and to assure continuity of service, a simple and reliable method of ignition and excitation had to be developed. Without touching upon the two methods formerly employed, i. e., d-c. — a-c. ignition and excitation, a new method, lately developed, which proved to be extremely serviceable in practise, is described and illustrated in detail. The simplicity of starting and operation, the ease of control and the adaptability to full automatic operation, as well as the high efficiencies of these rectifiers, are dealt with and all the advantages are recapitulated at the end. A somewhat exhaustive bibliography, which might be of value to future investigators, is also appended.