T PREFACE HERE is no more reliable piece of electrical apparatus than the arc lamp. With proper care, suitable carbons, and a uniform supply of power, it can be depended upon to meet its requirements, but any apparatus exposed to such hard usage as the arc lamp will sooner or later develop deficiencies which, if not promptly rectified, may lead to serious complications. It is with the idea of giving a few suggestions, of laying down a few rules, which, if followed, will increase the efficiency and raise the standard of arc lighting systems, that this book has been prepared. The suggestions offered are necessarily of a very general nature, since they refer to lamps of no particular manufacture and are equally applicable to all types. The authors have been associated with the Engineering Department of the National Carbon Company for a great many years, and their close contact with all types of arc lamps, all brands of carbons, and all arc systems, should, perhaps, enable them to take a more comprehensive view of common arc lamp practice than Engineers who are more directly interested in the development of some particular type. They will be pleased to take up individually any problem of daily practice which may not be covered by the suggestions outlined in this book. NATIONAL CARBON COMPANY PUBLICITY DIVISION 1911 Enclosed Arc Lamps Enclosed arc lamps may be divided into three general types, the multiple or constant potential, the series or constant current, and the series multiple or power circuit lamps. Each of these types is designed to meet certain service conditions. All three types are made for either direct or alternating current. D. C. lamps are preferable, due to their higher light efficiency and longer life, but the A. C. lamps are very often more desirable because of the more efficient transformation and transmission of electrical energy possible in A. C. systems. MULTIPLE ARC LAMPS. Multiple lamps are in very extensive use at present and are especially popular for indoor lighting on account of the low voltage required. They may be connected directly across 110 and sometimes on 220 volt circuits. Fig. 1. B Figure 1 shows the connections for a D. C. multiple lamp. There is only one set of magnet coils, R and S, and these are connected in series with each other and in series with the arc. These coils pull directly on the armature P, which operates the clutch C controlling the upper carbon. The operation of the lamp is as follows: When the current is first switched on, the carbons are touching each other and a strong current flows through the magnet coils. This attracts the armature P, raising the upper carbon and forming the arc. The current decreases as the carbons are separated until, when the arc is the proper length, the magnets are not strong enough to raise the upper carbon further. As the carbons are burned away the magnets are weakened and the clutch |